Locomotion and Movement Class 11 Biology Free Study Material in PDF

UNIT 1 - GENERAL INTRODUCTION TO HUMAN ANATOMY AND
PHYSIOLOGY AND TISSUE SYSTEM I
UNIT 2 - TISSUE SYSTEM II
UNIT 3 - INTEGUMENTARY SYSTEM
UNIT 4 - MUSCULAR SYSTEM
UNIT 5 - SKELETAL SYSTEM
STRUCTURAL ORGANIZATION AND HUMAN
PHYSIOLOGY: LOCOMOTION AND MOVEMENT

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1.1. LEVELS OF ORGANIZATION OF THE HUMAN BODY
Life is a complex continuum of flows of energy and matter. Discrete structures such as organs and
cells allow us to divide life into levels of organization. This organization is to some extent artificial, and
to some extent practical.
The human body is a complex, hierarchical system-that is a system made up of smaller subsystems
which are themselve made up of even smaller systems. We commonly study these different hierarchical
levels-levels of organization-separately. By breaking down the complex system into simpler parts, we
can make the whole system easier to understand. This “reductionist” approach, reducing a complex
system to simpler components is central to how we practice modern science.
Regarding the body, therefore, we consider the body as a whole, then its subsystems, and then the
components of these subsystems. We can model the hierarchy of organization within the body as
comprised of organs, tissues, cells, cell organelles, macromolecules, molecules and finally atoms.
The levels of organization that we will consider are from smallest to largest
• The chemical level, which consists of atoms, ions, and small molecules
• The macromolecule level, which consists of large molecules
• The cell level, which consist of individual cells; this is the smallest level that contains living
entities
• The tissue level, which consists of groups of related cells working together to perform specific
function
• The organ level, which consist of group of tissues working together to perform a higher - level
function
• The organ system level, which consists of all of the organs involved in performing a vital
function
• The organism or whole body level, which consists of a whole person
Although we will consider each level individually, it is important for you to keep in mind the connections
between the levels. Processes and events at one level can affect other levels. An alteration in the
structure of a protein (macromolecule level) can prevent a cell from functioning properly; this improper
function can affect the tissues, organs, organ system, and the whole body and the reverse is true:
changes to the body (organism level) can affect organs, tissues, cells and molecules.
UNIT 1 - GENERAL INTRODUCTION TO HUMAN ANATOMY AND
PHYSIOLOGY AND TISSUE SYSTEM I

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How body is organized?
Organelle
Tissue
Organ
Cell
Organ System
Organism
CHEMICAL LEVEL TISSUE LEVEL
Atoms
(C, H, O, N, P)
Smooth muscle cell
1
Stomach
Smooth muscle
tissue layers
Liver
4 ORGAN
LEVEL
2 CELLULAR
LEVEL
Molecule
(DNA)
5 SYSTEM LEVEL
ORGANISMAL
LEVEL
6
3
Large intestine
Small intestine
Digestive System
Smooth muscle tissue
Serous
membrane
Epithelial tissue
Esophagus
Stomach
Pancreas
Gall bladder
1.1.1. Tissues
In the body’s organizational hierarchy, tissues occupy a place between cells and organs. That is a
tissue is a group of cells with a similar shape and function. In turn, organs (which make up the body)
are comprised of various tissues.
The component cells of a tissue are a specific cell type. A tissue’s cell may be identical, but are not
necessarily so. Several tissues will comprise an organ. The body is made of dozens of different
tissues, but broadly speaking there are four types of tissues.
• Muscle tissue (in turn divided into skeletal, smooth and cardiac) is contractile. It allows
locomotion of the body. It also allows necessary contractions of various organs such as the
heart and of respiratory and digestive systems.
• Nerve tissue comprises the body’s wiring system. It conducts signals between the nervous
system and various organs.
• Connective tissue holds the body together. It is found in most organs, anchoring them to the
skeleton and other organs. Types of connective tissue include fibrous tissue, fatty tissue,
loose tissue and cartilage. Connective tissue also include bone, blood and lymph.
• Epithelial tissue is the body’s protection against the outside environment. Skin tissue helps to
maintain homeostasis. It helps monitor and control temperature and resists abrasion, foreign

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bodiesand damaging chemicals. Internally, epithelial tissue linesmost internal cavities, secreting
or absorbing nutrients.
1.1.2. Organs
An organ is made up of tissues that work together to perform a specific function for the body as
whole. Groups of organs that perform related functions are organized into organ systems, which
perform more general functions. The table below describes, the structures and functions of some
common organs.
Organ Primary function(s) Tissues it Organ system(s) it is a
contains part of
Brain Control of body system Nervous, connective, Nervous system, endocrine
and behavior; cognition epithelial system
Skin Protection; support and Epithelial, nervous, Integumentary system
containment; temperature connective, muscular
and fluid regulation
Stomach Chemical and mechanical Epithelial, connective, Digestive system
digestion of food muscular, nervous
Sternum Support; protection; blood Epithelial, connective, Skeletal system, immune
(breastbone) cell production nervous system, cardiovascular
system
Kidney Waste removal; fluid Epithelial, connective, Urinary system
regulation nervous

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1.1.3. Organ system
Organsystem are made up of organs that work together to perform a specific function for the body as
a whole.The table belowdescribesthe organ system and their primaryorgansandphysiological functions.
1.1.4 The whole body
The organ system of the body all work together to maintain proper physiological functions. Many
times in the arena of anatomy and physiology, including in this course, we closely examine the
molecules, cells, tissues and organs of the body to learn their forms and functions. However, it is
important to consider that every molecule works as part of the entire system. Endocrine disorders
such as diabetes affect glucose levels in the body. Altered blood glucose levels can affect many
organ systems. For example, the immune system may not heal as well, the urinary system may
experience kidney damage, and the cardiovascular system can experience vascular damage, even
to the point of causing blindness. In the body, everything is interconnected.
Organ system Key organ(s) Primary function(s)
Integumentary Skin Support; protection; regulation of fluid
levels and temperature
Skeletal Bones, cartilage Support; protection; movement; blood
cell production
Muscular Muscles, tendons Support; movement
Urinary Kidneys, bladder, urethra Waste removal; regulation of fluid
levels
Digestive Tongue, esophagus,stomach, Digestion of food; waste removal
small intestine, large intestine
gall bladder, rectum
Respiratory Trachea, lungs Gas exchange; regulation of
temperature
Cardiovascular Heart, blood vessels Transport of materials through the
body regulation of temperature
Nervous Brain, spinal cord Control of behavior and body systems;
cognition
Endocrine Glands Control of body systems and
development
Immune Thymus, tonsils, spleen Defense against infection
Lymphatic Lymph nodes, lymphatic vessels Immunity; regulating fluid balance
Reproductive Penis, testes, prostate (males); Reproduction
uterus, ovaries, vagina (females)

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1.2 TISSUES
Tissues are group of cells similar in structure, function and origin. Cells may be dissimilar in structure
and function but they are always similar in origin. Tissues form during development. Stem cells in the
embryo differentiate into various cell types. Different tissues arise from the source cells in each of the
three primary germ cell layers. For example, the epithelium is derived from the ectoderm and
endoderm. Connective tissue arises largely from the mesoderm.
4 basic types of tissues:
TARGET POINTS
 Bichat coined the term ‘tissue’.
 Histology: Study of tissue, word was given by Mayer; Father of histology - Bichat
 Microscopic anatomy: Detail study of tissue; founder - Marcello Malpighi
Epithelial tissue  Body’s protection against the outside environment
 Skin tissue helps to maintain homeostasis i.e. helps
monitor and control temperature and resists abrasion,
foreign bodies and damaging chemicals.
 Lines most internal cavities, secreting or absorbing nutrients
Connective tissue  Synthesizes and maintains a structurally competent
(CT) extracellular matrix, including a supporting and connecting
framework for all other tissue types
 Holds the body together
 Found in most organs, anchoring them to the skeleton and
other organs
 Types include: fibrous tissue, fatty tissue, loose tissue,
cartilage, bone, blood and lymph
Muscle tissue  Contractile tissue
 Allows locomotion of the body, necessary contractions of
various organs such as the heart and of respiratory and
digestive systems
 Divided into skeletal, smooth and cardiac.
Nerve tissue  Comprises the body’s wiring system, conducts signals
between the nervous system and various organs
helial tissue Connective tissue

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1.3 EPITHELIAL TISSUE
Epithelial = Epi (upon) + Thelia (growth)
1.3.1 Epithelial structure
 Word ‘Epithelium’ was given by- Ruysch.
 The only tissue in which cells are always arranged in uniform layer.
 High power of regeneration (it is absent or least in nervous tissue).
 Covers and lines organs / cavity walls; forms protective boundaries.
 Always rest upon underlaying connective tissue; are closely packed with very little intercellular
space due to which they are avascular but with innervations.
 Basement membrane: A thin non-living acellular membrane present between epithelium and
connective tissue
– Highly permeable
– Consist of 2 layers:
a. Basal lamina: Just below epithelium, made of glycoprotein secreted by epithelial cells.
b. Fibrous lamina: Just above connective tissue, collagen and reticular fibres are
suspended in mucopolysaccharide which is a matrix of connective tissue.
– Hence, basement membrane is secreted by both epithelium and conncetive tissue.
Secretory cells are found
in most epithelial layers.
These specialized cells
secrete substances onto
the surface of the cell
sheet
Cilia
Apical
Basement
membrane
Apical
Ciliated cells have cilia
on their free surface
that beat in synchrony
to move substances
(such as mucus) over
the epithelial sheet.
Nucleus
Epithelial structure
TARGET POINTS
 Mucopolysacharide is present in the form of hyaluronic acid which is composed of 2 components
- N acetyl D- glucosamine and glucuronic acid. Both these components are found in alternate form
- NAG - GA - NAG

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 To provide mechanical support for the tissue, plasma membrane of adjacent epithelium cells
modify to form the following structures (intercellular junctions):
1.3.2. Plasma membrane modification
Plasma membrane of free end gets modified to form 3 types of functional structures:
A. Microvilli
 Minute protoplasmic process which are non-motile, non-contractile.
 Help in absorption, secretion, excretion.
 Increase surface more than 20 times.
 Present in the wall of intestine, gall bladder, proximal convoluted tubule etc.
 Give a brush - border appearance when present in cuboidal / columnar epithelial cells.
B. Cilia or Kinocilia
 Long cylindrical protoplasmic process, motile and contractile.
 Originate from basal granule or kinetosome.
 Diameter of cilia is same from base to apex. In internal structure of cilia, 9 + 2 arrangement of
microtubules is present.
 Help in conduction of particles or mucus in a specific direction. Movement of cilia is in uniform
direction.
 Found in the inner surface of hollow organs eg. fallopian tube, trachea, uterus, ependymal
epithelium (inner lining of ventricles of brain and central canal of spinal cord. Function of cilia
is to conduct substances in CSF).
C. Stereocilia
 Long cytoplasmic process, non-motile, non-contractile.
 Basal granule is absent, plasma membrane is thick and rigid.
Interdigitation Finger like processes of plasma membrane which enter into cytoplasm of
adjacent cells. These structures are mainly found in transitional epithelium.
Desmosomes This type of (Macula Adherens) junction consists of disc - like protein plate
with intermediate fibre known as tonofibrils composed of keratin like sclero
protein. These filaments are deeply situated in the cytoplasm of respective
cell. These structures provide mechanical support to stratified epithelium.
They act as cementing to keep neighbouring cells together.
Tight junction At some places plasma membrane of adjacent cells become fused to form
tight junction. These structures are mostly found in columnar epithelium. These
stop substances from leaking across tissues.
Gap junction Allowcells to communicate with each other by connecting cytoplasm of adjoining
cells for rapid transfer of ions, small molecules and sometimes big molecules.

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 Base of stereocilia is broad and apical part is narrow, they are conical in shape.
 Increase surface area and found in epididymis, vas deferens
1.3.3 Types of epithelial tissue (based on number of layers of cells)
A. Simple epithelium (unilayered) - Simple squamous epithelium
(Functions as lining for body - Simple cuboidal epithelium
cavities, ducts and tubes) - Simple columnar epithelium
- Pseudostratified epithelium
B. Compound epithelium (multilayered) - Transitional epithelium
(Protective function) - Stratified squamous epithelium
- Stratified cuboidal epithelium
- Stratified columnar epithelium
C. Glandular epithelium
Apical surface
Basal surface Simple
Apical surface
Basal surface Stratified
Simple vs. Stratified epithelium
1.4. SIMPLE EPITHELIAL TISSUE
1.4.1. Simple squamous epithelium
Also called pavement epithelium or tessellated epithelium.
 Description: Single
layer of flattened cells
with disc shaped
central nuclei and
sparse cytoplasm; the
simplest of epithelia.
 Function: Allows passages of materials by
diffusion and filtration sites where protection is not
important; secretes lubricating substances in
serosae.
Simple squamous epithelium
Nucleus
Cytoplasm
Cell boundary

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Nucleus Basement membrane
Connective tissue
Basement
membrane
Cell
membrane
Nucleus
Cytoplasm
Simple cuboidal epithelium
 Location:
- Bowman’s capsule (Podocytes)
- Alveoli of lungs (Pneumocytes)
- Mesothelium: Covering of coelom is called as mesothelium (Tesselated)
(visceral and parietal peritonium, visceral and parietal pleura, visceral and parietal
pericardium)
- Endothelium: Inner lining of blood vessels and lymph vessels (Tesselated). Inner lining of
heart wall.
1.4.2. Simple cuboidial epithelium
Also called germinal epithelium because these cuboidal cells divide to form egg and sperm in gonads.
 Description: Single layer of cubelike cells with large, spherical central nuclei. Basement
membrane is present. Cells are of same length and width, so
they appear square in a vertical section.
 Function: Secretion, absorption and excretion; also forms
gametes in gonads.
 Location: Vesicles of thyroid gland, secretory unit of sweat glands, Acini of pancreas, iris
choroid, ciliary body of eye, thick part of ascending limb of loop of Henle, DCT of nephron,
peripheral region of ovary and lining of seminiferous tubules in testis.
 Modifications
A. When microvilli are present on free end of cuboidal cells, it is called as brush bordered
cuboidal epithelium. Found in PCT of nephron.
B. When cillia are present on free end of cuboidal cells, it is called as ciliated cuboidal epithelium.
Found in certain part of nephron and collecting duct.
1.4.3. Simple columnar epithelium
 Description: Single layer of tall cells with round to oval nuclei, some
cells bear cilia; layer may contain mucus, secreting unicellular glands
(goblet cells). Basement membrane is present.
 Function:Absorption; secretionof mucus, enzymes, and other substances
ciliated type propels mucus(or reproductive cells) by ciliaryaction.

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 Location: Non-ciliated type lines most of the
digestive tract (stomach to anal canal), gall
bladder and excretory
ducts of some glands;
ciliated variety lines small
bronchi, uterine tubes, and
some regions of the
uterus.
 Modifications
A. Brush bordered columnar epithelium: When microvilli are present on free end of columnar
epithelium eg. gall bladder.
B. Glandular columnar epithelium: Unicellular mucus secreting goblet cells are also present
in between columnar cells eg. stomach, colon, rectum
C. Glandular brush bordered columnar epithelium: When microvilli present on free end of
columnar cell and in between these cells goblet cells are also present eg. duodenum,
ileum, caecum.
D. Ciliated columnar epithelium: When cilia are present on free end of columnar cells
eg. fallopian tube, ependymal epithelium.
E. Stereociliated columnar epithelium: When stereocilia are present on free end of columnar
cells eg. epididymis, vas deferens.
1.4.4. Pseudostratified (ciliated / columnar) epithelium
 Description: Single layer of cells of differing heights, some not reaching the free surface;
nuclei seen at different levels; may contain mucus secreting goblet cells and bear cilia. In long
cells, elongated nucleus is present at the base of cell while in short cells, rounded nucleus is
present in the centre of cell. As nucleus in both cells are present on different levels, it appears
bilayered because few cells are too short to reach the top surface. But, all cells are present on
single basement membrane so it is unilayered.
Pseudostratified columnar and ciliated columnar
Goblet
cell
Mucus
Kinocilia
Basement
membrane
Cytoplasm
Nucleus
Long cell
Short cell
Basement
membrane
Nucleus
Connective
tissue
Microvilli

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 Function: Secretion, particularly of mucus; propulsion of mucus
by ciliary action.
 Location: Non-ciliated type in male’s sperm-carrying ducts and
ducts of large glands; ciliated variety lines the trachea, most of
the upper respiratory tract.
 Modifications
Pseudostratified ciliated glandular
epithelium:
In this epithelium, cilia are present of free
end of long cells and goblet cells are also
present in this epithelium eg. trachea,
bronchi, respiratory epithelium of nasal
chambers
1.4.5. Special types of simple epithelium
A. Neurosensory epithelium: In the structure of thisepithelium
in between piller shaped supporting cells modified sensory
cells are present. On the free end of sensory cell, sensory
hair is present by which they receive sensation. Base of
these cells is attached with sensory nerve.
Eg.- Gustatory epithelium - Covering of taste bud
of tongue receive taste sensation
- Olfactory epithelium - Schneidarian membrane receive
smell sensation.
- Stato - acoustic - Lining of internal ear.
- In retina of eye receive optic sensation.
B. Myoepithelium: Around mammary and sweat gland
C. Pigmented epithelium (cuboidal): In retina of eye.
1.5 COMPOUND EPITHELIUM
Limited role in secretion and absoption. To provide protection against chemical and mechanical
stress. On the basis of stretching ability it is of 2 types:
- Transitional epithelium: Stretchable
- Stratified epithelium: Non - stretchable
1.5.1. Transitional epithelium (urothelium)
 Description : Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal
or columnar; surface cellsdome shaped or squamouslike, depending on degree of organ stretch.
Trachea
Connective
tissue
Basement
membrane
Basal cells
Goblet cells
Cilia
Nerve fibrils
Columnar
cells
Neurosensory cells
Sensory hair

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 Function: Stretches readily and permits distension of urinary organ by
contained urine.
 Location: Lines the ureters, bladder and part of the urethra.
1.5.2. Stratified squamous epithelium (germinativum layer)
 Description: Thick membrane composed of several cell layers; basal
cells are cuboidal or columnar and metabolically active; surface cells
are flattened (squamous); in the keratinized type, the surface cells are
full of keratin and dead; basal cells are active in mitosis and produce
the cells of the more superficial layers.
 Function: Protects underlying tissues in areas subjected to abrasion.
 Location: Nonkeratinized type forms the moist liningsof the esophagus,
mouth, and vagina;
keratinized variety forms
the epidermis of the skin,
a dry membrane.
 Types: Based on presence of keratin proteins in outermost cells.
A. Keratinized stratified squamousepithelium: If keratin protein is present in scaly cells and cells
become non-nucleated dead cells eg. epidermis of skin, scale, horn, nails, feathers etc.
B. Non-keratinized stratified squamous epithelium: If keratin protein is absent. Cells are
nucleated and living. Eg. buccal cavity or oral cavity of mammals, inner lining of cheeks,
inner lining of lips, lining of hard palate, lining of tonsils, lower part of soft palate, pharynx,
oesophagus, anal-canal, lining of vagina, cornea of eye.
Epithelium Epithelial cells
Underlaying
connective
tissue
Stratified squamous
Horny layer
Intermediate
layers
Germinative
layer
Basement
membrane
{

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1.5.3. Stratified cuboidal epithelium
 Description: Generally two layers of cubelike cells:
innermost layer - cuboidal / columnar.
middle layer - polygonal shaped cells.
outermost layer - cubelike, nucleated and living cells.
 Function: Protection
 Location:
- Secretory duct of sweat glands, mammary glands and sebaceous gland, secretory duct of
sebaceous gland.
- Secretory duct of salivary glands, submandibular (Whartson’s duct), parotid (Stenson’s duct),
sublingual (Bartholin duct or duct or Rivinus).
- Pancreatic duct.
- Female urethra.
- Conjunctiva of eye.
1.5.4. Stratified colummar epithelium
 Description: Several cell layers; basal
cells usually cuboidal; superficial cells
elongated and columnar. Cells are
nucleated.
 Function: Protection; secretion
 Location: Rare in the body; small amounts in male urethra and in large ducts of some glands
 Types: Based on presence of cilia
A. Ciliated stratified columnar epithelium: Eg. buccopharyngeal cavity of frog, upper part of
soft palate towards nasopharynx, larynx, uterus
B. Non-ciliated stratified columnar epithelium. Cilia absent on free end. Eg. distal part of male
urethra, epiglottis
1.6 GLANDULAR EPITHELIUM
 Cells specialized to produce and secrete substance into ducts or into body fluids
 More cuboidal / columnar cells
1.6.1 Glands
A cell or a group of cells which secretes chemical substances are called glands. All glands are
composed of epithelium tissue. Glands can originate from all the three germinal layers.
Urethra

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1.6.2 Classification of glands
On the basis of presence of secretory duct
Endocrine glands Secretory duct absent, secrete hormones directly into the fluid bathing
the gland
Exocrine glands Secretory duct present - Liver (largest gland), secrete mucus, saliva,
oil, earwax, milk and enzymes
Heterocrine/mixed gland Both endocrine and exocrine partsare present eg. pancreas, gonadsetc.
On the basis of nature of secretion
Eccrine / Acrine / Secrete substances by simple diffusion (exocytosis). No part of
Merocrine glands cytoplasm is destroyed in secretion. Secretory matter is like water.
Eg.maximum sweat glands of humans, claws of rabbit, goblet cells,
salivary gland, tear gland, intestinal glands, mucous gland.
Apocrine glands Secretory products are collected in apical part of secretory cell and
apical portion is also shed alongwith secretory matter. Secretory cells
gain their lost part of cytoplasm by process of regeneration. Secretory
matter is comparatively concentrate. Eg. sweat gland of arm pit, pubic
region, skin around anus, lips, nipples etc. Largest sweat gland of
body are found around nipples - Areola mamme.
Holocrine glands Secretion is shed with whole cell leading to its destruction. Secretory
matter is concentrate. Eg. sebaceous, meibomian and zeis gland
Merocrine Apocrine Holocrine

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Simple
coiled
tubular
Simple
tubular
Simple
alveolar
Compound
tubular
Compound
alveolar
Compound
tubulo-
tubular
Based on secretory matter
Serous glands Secretion - watery fluid eg. sweat glands
Mucous glands Secretion - mucous / gelatinous eg. goblet cell
Mixed glands Secretion - watery + mucous eg. pancreas, gastric glands.
Based on number of cells
Unicellular glands Isolated glandular cell eg. goblet cells, Paneth cells
Multicellular glands Consist of cluster of cells.
Based on shape of secretory unit
Tubular glands A. Simple glands:
- Simple tubular glands eg. intestinal glands (crypts of
Leiberkuhn)
- Simple coiled tubular eg. sweat glands
- Simple branched tubular, eg. gastric glands
B. Compound tubular glands: Eg. Brunner’s gland,
mammary glands of prototheria, inactive mammary
glands of eutheria
Saccular / Alveolar glands A. Simple glands:
- Simple alveolar eg. cutaneous glands of frog, poison
glands, mucous glands
- Simple branched alveolar eg. sebaceous glands.
B. Compound alveolar glands: Eg. sublingual glands,
submandibular glands
Compound tubulo-saccular glands Eg. active mammary glands, parotid gland, pancreas

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1. The type of tissue lining the nasal passage,
bronchioles and Fallopian tubes is
a) Columnar ciliated epithelium
b) Cuboidal epithelium
c) Neurosensory epithelium
d) Germinal epithelium
2. Areolar tissue
a) Is made of threads crossing each other
and leaving a space between them
b) Stores fat
c) Is found in mammary gland
d) Is found in hyaline cartilage
3. The three germinal layers of the gastrula
give rise to
a) Epithelial tissues
b) Muscular and nervous tissue
c) Connective tissue
d) All of the above
4. Squamous epithelium is also called
a) Germinal epithelium
b) Columnar epithelium
c) Pavement epithelium
d) Sensory epithelium
5. An organ is a
a) Group of two or more kinds of tissue,
united structurally and coordinated in
their activities
b) Group of similar cells that function
together in a specialised activity
c) Multilayered sheet of cells
d) Solid structure formed of embryonic
mesoderm
6. Characteristic of simple epithelium is
a) They are arranged indiscriminately
b) They make a definite layer
c) Continue to divide and help in organ
function
d) None
Simple Questions
7. Who is father of microscopic anatomy?
a) Bichat b) Reyush
c) Malpighi d) Hartwig
8. Compound squamous epithelium occurs in
a) Stomach b) Pharynx
c) Intestine d) Trachea
9. Cells of peritoneum comprise
a) Ciliated epithelium
b) Glandular epithelium
c) Columnar epithelium
d) Squamous epithelium
10. Glands are formed of
a) Secretory epithelial cells
b) Transitional epithelial cells
c) Stratified columnar cells
d) Pseudostratified epithelial cell
11. Epithelial cells get nutrients from
a) Neighbouring cells
b) Blood vessels
c) Lymph vessels
d) Underlying tissue
12. Gap junctions
a) Help to stop substances from leaking
across a tissue
b) Perform cementing to keep neighbouring
cells together
c) Provide stretchability to the epithelium
d) Facilitate the cells to communicate with
each other by connecting the cytoplasm
of adjoining cells
13. Assertion: Epithelium cells get their
nutrients from adjacent cells.
Reason: In epithelium tissue large
intercellular spaces are present.
a) A b) B
c) C d) D

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14. Basement membrane is composed of
a) Hyaluronic acid + glycoproteins
b) Only mucopolysacharides
c) Endodermal cells
d) Epidermal cells
15. The type of epithelium found in conjunctiva
of eye is
a) Stratified cuboidal
b) Stratified columnar
c) Stratified squamous
d) Transitional epithelium
16. Inner line of vagina is composed of
a) Stratified ciliated columnar epithelium
b) Cuboidal epithelium
c) Simple squamous epithelium
d) Stratified squamous epithelium
17. Epithelium of bronchioles is
a) Simple cuboidal
b) Pseudostratified columnar
c) Simple squamous
d) Pseudostratified sensory
18. Vertebrate salivary glands and exocrine part
of pancreas are
a) Apocrine b) Holocrine
c) Epicrine d) Merocrine
19. Stratified squamous epithelium is found in
a) Buccal cavity b) Stomach
c) Intestine d) Spleen
20. Which type of tissue forms glands?
a) Epithelial b) Connective
c) Nervous d) Muscular
21. Gastric glands are
a) Simple tubular
b) Simple coiled tubular
c) Branched tubular
d) Compound tubular
22. Which of the following cells does not divide
once but only differentiate?
a) Interstitial cells b) Nerve cells
c) Blood cells d) Glial cells
23. Bowman’s capsule of mammalian nephron
is lined by
a) Columnar epithelial cells
b) Squamous epithelial cells
c) Cuboidal epithelial cells
d) Ciliated columnar epithelial cells
24. The oil substance secreted by the
ceruminous gland in the ear is called
a) Ear wax b) Cerubimen
c) Oil d) Mucin
25. Goblet cells are a type of
a) Multicellular gland
b) Intracellular gland
c) Unicellular gland
d) Intercellular gland
26. An example of holocrine gland is a
a) Sweat gland b) Salivary gland
c) Pancreatic gland d) Sebaceous gland
27. The cell membranes of adjacent cells are
fused at this cell junction
a) Macula adherens
b) Zonula adherens
c) Zonula occludens
d) Nexus
28. Simple squamous epithelium is found in
a) Lining of intestine
b) Henle’s loop
c) Seminiferous tubule
d) Uriniferous tubule
29. Adjacent epithelial cells are held together
by means of
a) Microsomes b) Liposomes
c) Desmosomes d) Glyoxysome

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30. Select the correctly matched pair
a) Cuboidal epithelium - Blood vessels
b) Columnar epithelium - Uterine
endometrium
c) Simple epithelium - Nasal cavity
d) Stratified epithelium - Thyroid follicles
31. Sweat glands are
a) Merocrine
b) Endocrine
c) Holocrine
d) None
32. Extracellular basement membrane is the
peculiarity of
a) Nervous tissue
b) Vascular tissue
c) Epithelial tissue
d) Connective tissue
33. The protein deposited in the dead superficial
cells that makes the skin epithelium
impervious to water is
a) Mucus
b) Elastin
c) Keratin
d) Collagen
34. Pigmented epithelium is found in
a) Iris b) Retina
c) Choroid d) Cornea
35. Epithelial lining of cornea is composed of
a) Stratified squamous non-keratinised
b) Transitional
c) Simple cuboidal
d) Simple squamous
36. Desmosomes
a) Connect the epithelial cells
b) Types of lysosomes
c) Granules of muscle fibres
d) Found in bone
37. Cutaneous gland of frog are
a) Tubular
b) Simple alveolar
c) Compound alveolar
d) Compound tubular
38. Lining of salivary glands is made up of
a) Stratified Squamous epi.
b) Stratified Cuboidal epi.
c) Stratified columnar epi.
d) Transitional epi.
39. Secretory duct of mammary gland is
composed of
a) St. cuboidal epithelium
b) St. columnar epithelium
c) St. squamous epithelium
d) Pseudostratified epithelium
40. Term tissue is coined by (for animal
anatomy)
a) Bichat b) Mayer
c) Malpighi c) Hertwig

21
1. Olfactory epithelium (Schneiderian
membrane) is composed of
a) Neurosensory epithelium
b) Simple sq. epithelium
c) Simple cuboidal
d) Germinal epithelium
2. Debove’s membrane is a layer of
a) Muscular tissue b) Epithelial tissue
c) Connective tissue d) All of these
3. Mesothelium is
a) Lining of coelom which originated from
mesoderm
b) Lining of coelom which originated from
ectoderm
c) Lining of heart which originated from
Endoderm
d) Lining of heart which originated from
Mesoderm
4. Which gland secretes chemical by simple
diffusion?
a) Apocrine gland b) Holocrine gland
c) Merocrine gland d) None
5. Stereocilia present in
a) Epididymis b) Seminal vesicle
c) Ureter d) Kidney
6. Which of the following is correct match of
epithelial tissue?
Difficult Questions
7. Which of the following is made up of cube
like cells?
a) Epithelium of fallopian tubes
b) Epithelium of PCT
c) Epithelium of stomach
d) Epithelium of alveoli
8. Germinal epithelial cells are present in
a) Seminiferous tubules
b) Uriniferous tubules
c) Lining of stomach
d) Inner lining of trachea
9. Which of the following serve as the
anchoring junctions between the cells?
a) Tight junctions b) Gap junctions
c) Desmosomes d) Nexuses
10. Find out the incorrect match
A Ciliated - Bronchioles and
epithelium Fallopian tubes
B Compound - Ducts of salivary
epithelium glands
C Dense regular - Tendons and
connective tissue Ligaments
D Areolar tissue - Present in the
skin
a) A and C b) B and C
c) A and D d) Only D
11. Embryonic mesoderm forms the
a) Endothelium of blood vessels
b) Exocrine cells
c) Endocrine cells
d) Glial cells
12. Glands of vertebrates are orginated from
a) Ectodermal b) Endodermal
c) Mesodermal d) All the above
13. Ependyma is
a) Ciliated pseudostratified columnar
b) Ciliated columnar
c) Ciliated cubical epithelium
d) Non Ciliated Columnar
a) Squamous Bronchioles and
epithelium fallopian tube
b) Columnar Ducts of glands
epithelium and tubular part
of nephron
c) Cuboidal Walls of blood
epithelium vessels and air
sacs of lungs
d) Compoud Buccal cavity
epithelium and pharynx

22
14. Inner lining of gut, stomatch and liver is
made up of
a) Simple squamous
b) Simple cuboidal
c) Simple columnar
d) Pseudostratified epithelium
15. An epithelium with water proofing qualities
is
a) Stratified cuboidal
b) Stratified columnar
c) Stratified squamous
d) Transitional epithelium
16. Assertion: Simple cuboidal epithelium is
also called as germinal epithelium.
Reason: Cuboidal cells of gonads forms
gametes.
a) A b) B
c) C d) D
17. Identify the glands (A) and (B) shown below
and select the right option for location and
function
A
B
18. Choroid of eye lined by
a) Cuboidal epithelium
b) Squamous epithelium
c) Ciliated epithelium
d) Columnar epithelium
19. Tessellated epithelium is present in
a) Ependymal menbrane
b) Endothelium
c) Schneiderian membrane
d) Alveoli of lungs
20. Endocrine glands
a) Secrete hormones
b) Are ductless glands
c) Also secrete enzymes
d) Both (a) and (b)
21. The four sketches (A, B, C and D) given
below represent four different types of
animal tissues.
A B
C D
Gland Location Function
a) A Unicellular Alveoli Secrete
gland saliva
b) B Multicellular Oesophagus Secrete
gland enzyme
c) A Multicellular Alimentary Secrete
gland canal mucus
d) B Multicellular Buccal Secrete
gland cavity saliva
Tissue Location Function
a) B Simple Fallopian tube Transport
squamous of gamete
epithelium
b) C Simple Wall of blood Diffusion
cuboidial vessels and boundary
epithelium air sac of lungs
c) D Compound Skin Protection
epithelium
d) A Simple Tubular part Secretion
columnar of nephron
epithelium

23
ANSWER KEYS
Simple Questions
1.a 2.a 3.d 4.c 5.a 6.b 7.c 8.b 9.d 10.a 11.d 12.d
13.d 14.a 15.a 16.d 17.c 18.d 19.a 20.a 21.c 22.b 23.b 24.a
25.c 26.d 27.c 28.b 29.c 30.c 31.a 32.c 33.c 34.b 35.a 36.a
37.b 38.b 39.a 40.a
Difficult Questions
1.a 2.b 3.a 4.c 5.a 6.d 7.b 8.a 9.a 10.d 11.a 12.d
13.b 14.c 15.c 16.a 17.d 18.a 19.b 20.d 21.c

24
1. In transitional epithelium
a) Innermost layer is cuboidal rest on
underlying connective tissue
b) Innermost layer is columnar rest on
underlying connective tissue
c) Innermost layer is pear shaped rest on
basement membrane
d) Innermost layer is umbrella shaped rest
on underlying basement membrane
2. Lining of sebaceous duct is composed of
a) Cuboidal stratified epithelium
b) Stratified squamous
c) Simple columnar
d) Simple squamous
3. Lining of larynx is
a) Stratified ciliated columnar epithelium
b) Stratified squamous epithelium
c) Stratified cuboidal epithelium
d) Stratified columnar epithelium
4. Vesicles or acini of thyroid gland is
composed of
a) Simple squamous epithelium
b) Simple cuboidal epithelium
c) St. squamous epithelium
d) St. cuboidal epithelium
5. Compound tubulo alveolar gland is
a) Parotid gland
b) Brunner’s gland
c) Submandibular gland
d) Sebaceous gland
DPP - 1
6. Stretchable and water proof epithelium
a) Simple cuboidal
b) Simple squamous
c) Simple columnar
d) Transitional
7. Exoskeleton originate from (eg. feathers
nail, horn, hoofs)
a) Connective tissue proper
b) Epithelium tissue
c) Skeletal tissue
d) Vascular tissue
8. Vagina, esophagus, urethra contain which
type of tissue?
a) Stratified squamous epithelium
b) Simple squamous epithelium
c) Ciliated epithelium
d) Columnar epithelium
9. The cavities of alveoli of lungs are lined by
a) Cuboidal epithelium
b) Columnar epithelium
c) Stratified cuboidal epithelium
d) Squamous epithelium
10. Which type of tissue forms the inner lining
of a blood vessel?
a) Epithelial b) Connective
c) Nervous d) Muscular

25
2.1 CONNECTIVE TISSUE
 O. Hartwig called them ‘Mesenchyme’ as they originated from the embryonic mesoderm
 Constitutes 30% of total body weight: Muscle - 50%, epithelium - 10%, nervous - 10%
 Most abundant and widely distributed for linking and supporting.
 3 types based on matrix:
1. Connective tissue proper: Matrix soft and fibrous
2. Connective tissue skeleton: Dense and mineralised matrix, due to deposition of minerals
it becomes hard
3. Connective tissue vascular: Liquid and fibre free matrix.
2.2 CONNECTIVE TISSUE PROPER
2.2.1. Components
A. Cells
1. Fibroblast cells
 Largest cell of connective tissue proper; maximum in number.
 Cell body is oval shaped with oval shaped nucleus.
 Branched cytoplasmic process arise from these cells so they appear irregular. Cytoplasm is
rich in rough ER.
 Function: To produce fibres (fibres are composed of protein) and synthesize most part of
matrix of connective tissue.
 Old fibrocytes are inactive cells and synthesize only little part of matrix.
 Also considered as undifferentiated because they can be modified into Osteoblasts and
Chondrioblasts to produce bone and cartilage.
2. Plasma cell (Cart wheel cell)
 Less in number, small in size, amoeboidal in shape.
 Rounded nucleus is present ; chromatin is arranged like spokes (radial rows) in wheel so also
called as Cart wheel cells.
 Formed by the division of lymphocytes hence, also called as clone of lymphocytes.
 Function: To produce, secrete and transport antibodies.
3. Mast cells (Mastocytes)
 More in number, smaller in size, amoeboidal in shape
 Are like basophils in structure and function.
 ‘S’ shaped nucleus is present which is divided into 2 or 3 lobes and lobes are interconnected
by protoplasmic strands.
UNIT 2 - TISSUE SYSTEM II

26
 Cytoplasm contains basophilic granules that can be stained with basic dye methylene blue.
 Functions: Synthesis of proteins and matrix (by mast cells)
a) Histamine: It is a vasodilator, increases blood circulation in affected area. It also increases
the permeability of blood capillaries.
When allergic substances enter body, mast cell stimulates and secretes histamine so a
part of blood comes out from blood capillaries with WBC and accumulate in intercellular
spaces. This part of blood is called as exudate which causes swelling in affected area.
The swelling is red, warm and painful and called inflammation.
b) Serotonin: Also called as 5-hydroxy tryptamine. It is a vasoconstrictor. At the site of cut or
injury, mast cell secretes serotonin which decrease high blood loss.
c) Heparin: It is a mucopolysaccharide and a natural anti-coagulant. It prevents clotting of
blood in uninjured blood vessels and prevents the conversion of prothrombin into thrombins.
TARGET POINTS
 Other natural anticoagulants are
Hirudin - found in leech.
Anophelin - found in female Anopheles.
Lampredin - found in Petromyzon.
Cumerin - obtain from plants.
Warfarin - obtain from plants.
 To collect blood in the bottle in blood bank artificial anticoagulants are used like sodium citrate,
sodium oxalate, EDTA (Ethylene diamine tetra acetic acid). These chemicals act as calcium
binding units and remove 2
Ca
ions from blood.
4. Adipose cells
 Oval shaped cells, stores fat.
 On the basis of number of fat globules, adipocytes are of two types:
a) Monolocular adipocytes:
– Single large and central fat globule is present.
– Nucleus and cytoplasm is peripheral; cytoplasm is less in amount.
– Due to compression of fat globule, nucleus becomes flattened in shape.
– These adipocytes form white fat.
b) Multilocularadipocytes:
– Many small fat globules are distributed in the cytoplasm around nucleus
– Cytoplasm is more in quantity
– Nucleus is rounded and central
– These adipocytes form brown fat.

27
5. Mesenchymal cells
 Less in numbers, small sized with cytoplasmic process having irregular shape.
 Oval shaped nucleus present.
 Are undifferentiated cells of connective tissue (pluripotent).
 Function: Forms other cells of connective tissue.
6. Macrophages (Histiocytes)
 2nd
largest in size and 2nd
maximum in number.
 Amoeboidal in shape with bean (Reniform) or kidney shaped nucleus.
 Cytoplasm quantity is more and agranular but due to presence of more number of lysosome it
appears granular.
 Phagocytic in nature, destroy bacteria and viruses. They arise by the fusion of monocytes.
 Also called as scavenger cells of connective tissue as they destroy dead or damaged cells to
clean connective tissue.
 Macrophages of
Lungs - Dust cells Brain - Microglial cells
Liver - Kupffer cells Thymus gland - Hessel’s granules
Blood - Monocytes Spleen - Reticular cells
7. Lymphocytes
 Less in number and small in size having amoeboidal shape.
 Large nucleus is present and cytoplasm is present as peripheral layer in less quantity.
 Function: Produce, transport and secrete antibodies.
 Divide to form plasma cells of connective tissue proper.
B. Fibres
1. Collagen fibres (White fibres)
 Bright and white fibres made of collagen (Tropocollagen).
 Present in maximum quantity in vertebrates and constitutes one third part of connective tissue
fibres.
 Wavy and tough fibres arranged in bundles called fascia.
 In fascia, elasticity is absent but in single collagen fibre, very less elasticity is present.
 On boiling, convert into gelatin.
 Are digestible by pepsin enzyme.
2. Elastic fibres (Yellow fibres)
 Yellow in colour and made of elastin.

28
Fibroblast
Collagen fibres
Areolar tissue
 Are branched fibres but arranged singly. Branches form network.
 Maximum elasticity is present and are highly resistant to chemicals. When boiled they do not
dissolve.
 Are digestible by trypsin enzyme.
3. Reticular fibres
 Also known as arzyrophil fibre since they can be stained with silver salts.
 Are made of reticulin protein.
 Highly branched and form dense network.
 Delicate, elasticity is completely absent.
 Mainly distributed in lymphoid organs like spleen or lymph nodes.
C. Matrix (Ground substance)
 Composed of mucopolysaccharide present in the form of hyaluronic acid.
2.2.2 Types of connective tissue proper
A. Areolar connective tissue
 Also known as loose connective tissue or spongy tissue.
 Most widely distributed tissue in the body.
 Maximum intercellular space or substances / matrix is present.
 Due to irregular arrangement of bundle of collagen fibres many gaps called Areolae are present.
In areolae, other components of connective tissue are distributed like fibres, cells and matrix.
 Few elastic fibres are present but reticular fibres and reticular cells are completely absent.
 In cells, mast cells, macrophage and fibroblast are more in number.
 Areolae blood vessels and nerve fibres are also present.
TARGET POINT
 Tela Subcutanea: A thin continuous layer which connects skin with underlaying skeletal muscles
(Panniculas camosus). In mammals, skin is tightly attached with muscles.
While in frog, it is present in the form of septum so skin is loosely attached with muscles.
Endomysium - Around single muscle fibres.
Perimysium -Around bundle of muscle fibres.
Endoneurium - Around single nerve fibres.
 Location: Outside of seminiferous tubules,
medulla of ovary, submucosa of trachea,
bronchi, intestine.

29
B. Adipose connective tissue
 Modification of areolar connective tissue. But in areolae, major component is adipocytes which
store fats. Blood vascular system is also present in this tissue.
 If this tissue is treated with alcohol (organic solvent), fat will be dissolved completely and
adipocytes will become vacuolated.
 Can be stained with sudan solution.
 On the basis of adipocytes 2 type of fats are found in animals:
1. White fat: Composed of monolocular adipocytes with a single large fat globule, peripheral
cytoplasm and peripheral nucleus is present. Due to less amount of cytoplasm, mitochondria
are also less in number. So they produce less energy.
Eg. Panniculas adiposus: A thin continuous layer of white fat under the dermis of skin which
isalso called hypodermis of skin. Panniculas adiposus is absent in skin of rabbit. Fat is collected
in form of adipose connective tissue as a
discontinuous layer.
Blubber: Thick layer of white fat found
under dermis of skin. Found in whale, seal
elephants. Maximum thickness of this
layer is found in blue whale (80 cm.).
Hump of camel, tail of marino sheep
and yellow bone marow.
2. Brown fat: Composed of multilocular
adipocytes with many fat globules.
Cytoplasm is more in amount. Due to more number of mitochondria, it produces 20 times
more energy than white fat. Brown colour of fat is due to presence of cytochrome pigment.
Cold resistance device in new born baby is due to presence of brown fat.
Rodents like rat, shrew obtain energy from stored brown fat during hibernation.
When fat is oxidised it produces water and energy.
C. White fibrous connective tissue
 Bundle of collagen fibres are more
in quantity and other components of
connective tissue proper are less in
quantity.
 Yellow fibres and reticular fibres are
completely absent.
 In cells, fibroblast and mast cells are more in number.
 Based on arrangement of fibres and matrix this tissue occurs in dense and irregular forms.
Fat storage area
Nucleus
Plasma membrane
Collagen fibers
Dense regular CT Dense irregular CT
Fibroblast nuclei
Collagen fiber bundles

30
a) Cord:
1. Bundle of collagen fibres and matrix are distributed in regular alternate pattern.
2. Fibroblast cells are arranged in a series. Mast cells are scattered in matrix.
Eg. Tendon: A structure which connects muscles and bones.
b) Sheath: There is no regular pattern of fibres and matrix. Cells and fibres are criss - crossed
arranged.
Eg. Pericardium
Periosteum - Outer covering of bone.
Perichondrium - Outer covering of cartilage
Epimysium - Covering of muscle.
Renal capsule - Around kidney.
Tunica albugenia - Covering of testis.
Splenic capsule - Covering of spleen.
Duramater - Outermost covering of brain.
Glison’s capsule - Around lobe of liver.
Cornea of eye
Tunica adventia of trachea, bronchi, oesophagus
D. Yellow fibrous connective tissue
 Yellow fibres are more in quantity but collagen fibres are also present.
 Reticular fibres are absent.
 On the basis of distribution of fibres and matrix they are of two types
a) Cord: Bundle of collagen fibres and matrix distributed in a regular pattern and in matrix
yellow fibres form network.
Eg. Ligaments - A structure which connects bones.
b) Sheath: Irregular distribution of fibres and matrix with elastic fibre.
Eg. Wall of alveoli of lungs, small bronchioles, lymph vessels and blood vessels and true
vocal cords
TARGET POINTS
 Strongest tendon of the body is Tendocalcaneus tendon. This connects gastrocnemius muscle
of shank with calcaneum bone of ankle.
 Strongest ligament of body is Ilio femoral ligament. This ligament connects Ilium bone of pelvic
girdle with femur bone of hind limb.
 Another strongest ligament ligamentum flava, present between two adjacent vertebrae.
 In quadrupeds like cow and buffalo strongest ligament is ligamentum nuchea present in the
neck between two cervical vertebrae.

31
E. Reticular fibrous connective tissue
 Also called lymphoid tissue, mostly found in lymphoid organs.
 Matrix of this tissue is like lymph.
 Reticular fibres are more in amount and form dense network around reticular cells. Lymphocytes
are also more in number.
 Provide support and strength and form the stroma (frame work) of soft organs.
Eg. Spleen, lymph nodes (tonsils, Peyer’s patches), cortex of ovary, endosteum (covering of
bone marrow cavity), lamina propia of trachea, bronchi, intestine.
F. Mucoid connective tissue
 Also called embryonic tissue because it is mainly found during embryonic life.
 Matrix is in abundance. Few collagen fibres and fibroblast cell may be present.
 Matrix is composed of jelly like material called Wharton’s Jelly.
Eg. Umbilical cord (connects placenta with foetus), vitreous humor in vitreous body of eye,
comb of cock.
G. Pigmented connective tissue
 Modification of areolar connective tissue but in areolae, pigmented cells are more in number
known as Chromatophores which provide colouration.
Melanophore - Melanin - Black colour.
Guanophore - Guanine - White colour.
Xanthophore - Xanthophil - Yellow colour.
Eg. Dermis of frog skin, iris and choroid of eye.
2.3 CONNECTIVE TISSUE SKELETON
 Matrix is dense and mineralised. Due to deposition of minerals it becomes hard.
 Also known as supporting tissue i.e. provides support to body
 2 types: Cartilage and bone.
2.3.1 Cartilage
 Outermost covering, Perichondrium is composed of white fibres connective tissue.
 Cartilage producing cells arranged on periphery of cartilage are Chondrioblast. These are
active cells and divide to form chondriocytes, and synthesize the matrix of cartilage.
 Mature cells of cartilage is called Chondriocytes. They are found in vacuole like space in
matrix called Lacuna in which 1-4 Chontrocytes are present.
 Chondrioclast are cartilage destroying cells.
 Matrix of cartilage is called chondrin composed of chondromucoprotein having Chondroitin-
6-sulphate and mucopolysaccharide (hyaluronic acid).

32
 Chondrin provides rigidity and elasticity to cartilage (matrix solid, pliable and resistscompression)
 Blood circulation is absent in chondrin but blood supply is present in perichondrium.
 Types of cartilage: A. Hyaline cartilage.
B. Fibrous cartilage - (a) Elastic cartilage (b) White fibrous cartilage
C. Calcified cartilage
A. Hyaline cartilage
 Maximum in human body.
 Most part of embryonic skeleton is composed of this cartilage thus, maximum bones of body
are cartilagenous bones.
 Perichondrium is present.
 Matrix is glass like clear or hyaline matrix because fibres are completely absent in the matrix.
Only few collagen fibres may be present.
 Colour of matrix is bluish and it is translucent.
 Eg. Nasal septum
‘C’ shaped rings of trachea and bronchi (incomplete in dorsal surface).
Sternal part of ribs (coastal cartilage).
Larynx
Articular cartilage: At the junction of two long bones on articular surface. At the end of long
bone periosteum is absent and hyaline cartilage is present known as articular cartilage.
B. Fibrous cartilage
1. Elastic cartilage
 In the matrix of this cartilage yellow fibres form networks and thus, make it highly flexible.
 Colour of matrix is pale yellow.
 Eg. Tip of nose, ear pinna (outer ear joint), epiglottis, wall of eustachian tube
2. White fibrous cartilage
 Perichondrium is absent (only in WF cartilage) because complete WFCT is converted into
cartilage.
 In matrix bundle of collagen fibres are more in quantity (strongest cartilage).
 Eg. Pubic symphysis: Pubis bone (half part of pelvic girdle Os innomineta) are interconnected
by pubic symphysis.
Intervertebral disc: A pad of cushion like structure which absorbs mechanical shock and
jerks and protects vertebral column. Central part of this disc is soft called as nucleus
pulposus. Slight elongation of body after death or in sleeping posture is due to relaxation
of this disc.

33
C. Calcified cartilage
 Modified hyaline cartilage but due to deposition of calcium salts its matrix becomes hard like
bones.
 Hardest cartilage of the body.
 Ca salt deposits in the form of hydroxyapatite (Ca (PO ) (OH) )
10 4 6 2
 Eg. Pubis of frog’s pelvic girdle, supra scapula of pectoral girdle, head of femur and humerus.
2.3.2 Bone
 Study of Bone - Osteology
 Process of bone formation - Ossification
 Hardest tissue - Bones, Softest tissue - Blood
 Hardest substance - Enamel. It is not a group of cell but formed by the secretion of ameloblast
cells of teeth.
 Outermost covering of bone is periosteum composed of white fibrous connective tissue.
 Bone producing cell iscalled osteoblast. They divide to form osteocyte and synthesize organic
part of matrix.
 Mature cell of bone is called osteocyte, found in lacuna. Only one osteocyte is found in lacuna.
 Bone destroying cells are osteoclasts.
 Matrix - Hard and non-pliable. It has two parts:
– Inorganic part (65-68%): 2
4
3 )
(PO
Ca - 80% max, rest 20% 3
CaCO (10%), 3 4 2
Mg (PO ) (10%),
Fluorides (very less).
– Organic part (32-35%): Ossein in which bundle of collagen fibres suspended in sulphated
mucopolysaccharide.
 Sharpay’s fibre: Extra bundle of collagen fibres present in the outermost layer of matrix. They
are also found in the cement of teeth and provide extra mechanical support to bone.
A. Structure of long bone
Long bone has three regions:
1. Epiphysis:
– Ends of long bone
– Composed of spongy tissue.
– If present at the joint then on articular surface periosteum is absent and articular cartilage
(hyaline cartilage) is present.
– Cavity is present in the form of trabeculae filled with red bone marrow. It is composed of
myeloid tissue which produces blood corpuscles so epiphysis act as a hemopoietic organ.

34
2. Diaphysis:
– Middle part or shaft of long bone.
– Composed of compact bone.
– Hollowcavity is present called bone marrow
cavity filled with yellow bone marrow
composed of white fat.
– Function of YBM is storage of fat.
– If required or essential in anaemic condition,
YBM is replaced by RBM.
– At the time of birth RBM is 70 ml while in
adult it is about 4 litre.
3. Metaphysis:
– Formed little part between epiphysis and diaphysis.
– Epiphyseal plate is present made up of osteoblast cells. They divide to form osteocyte and
also synthesize matrix of bone. Epiphyseal plate is responsible for bone elongation.
– After complete development of long bone this plate is destroyed. So, in completely developed
bone only 2 regions are found while in a developing bone 3 regions are present.
B. Internal structure of mammalian bone
It has the following major structures:
1. Periosteum
 Outermost covering of bone
 Consists of two layers : Outer layer consists of WFCT in which blood circulation is present.
Inner layer consists of single layer of osteoblast cells.
 They divide to form osteocyte and secrete layers of matrix.
Concentric lamellae
Endosteum
Periosteum
}
} Concentric lamellae
Haversian canal
Lamellae
Lacuna
Canaliculi
Interstitial
lamellae
T. S. of Mammalian long bone
}
}
Haversian
system
Epiphysis
Metaphysis
Cancellous (spongy)
bone with red bone
marrow
Compact bone
Marrow cavity with
yellow bone marrow
Periosteum
Endosteum
Long Bone
Diaphysis
(shaft)
Metaphysis
Epiphysis

35
2. Matrix
 Composed of inorganic and organic compounds.
 In matrix, two types of canals are present:
a) Haversian canal: Longitudinal canals arranged parallel to long axis of bone. One or two
blood capillaries and nerve fibres are present.
b) Volkmann’s canal: These are transverse/horizontal or oblique canals. Haversian canals are
interconnected by Volkmann’s canal. Matrix of bone is synthesized in the form of layer called
lamellae. On the basis of arrangement three types of lamellae are present in the matrix:
i) Haversian lamellae
– Concentric layers of matrix present
around Haversian canal.
– Between these lamellae, layer of
osteocyte cells are also present.
– Haversian canal, Haversian lamellae
and osteocyte form Haversian system
or osteon.
– Presence of Haversian system is a
typical feature of mammalian compact
bones.
– Osteocytes are present in the lacuna. Each osteocyte is interconnected with adjacent
osteocyte by their cytoplasmic process.
– Cytoplasmic processes are present in the canals of lacuna called as canaliculi.
ii) Interstitial lamellae
– These layers of matrix are present in the space between two Haversian systems.
iii) Circumferential lamellae
– Are of two types:
Outer circumferential lamellae: Present around all Haversian system, these are
peripheral layers of matrix.
Inner circumferential lamellae: Present around bone marrow cavity.
3. Endosteum
 Endosteum consists of two layers:
– Towards bone marrow cavity layer lined with reticular fibrous connective tissue.
– Towards matrix of bone endosteum lined with layer of osteoblasts which divide to form
osteocytes and sythesize matrix. So growth of bone is bidirectional (periphery and central
region) while growth of cartilage is unidirectional.
Protoplasmic
processes
Bone cell
Cytoplasm
Nucleus

36
4. Bone marrow cavity
 In the central region, hollow cavity is present filled with YBM.
 Composed of white fat.
 Function: Collection of fats or storage of fats.
C. Types of bones
On the basis of development or location of ossification:
1. Cartilagenous bones/Replacing/Endochondral bone
 Developed from cartilage or formed by the ossification of cartilage.
 In their formation, two types of cells are required.
– Chondrioclast: Reabsorb cartilagenous matter.
– Osteoblast: Deposit bony matter into cartilage, so cartilage is replaced by bone. Hence,
these bones are also called as replacing bones.
 Eg. Maximum bones of our body like limb bones (fore and hind), ribs.
2. Membranous bones/Dermal bones/Investing bones
 These bones are developed from the connective tissue of dermis or formed by ossification in
the connective tissue of dermis.
 Eg. Pubis, sternum, nasal bone, clavicle, vomer bone (present in the posterior part of nasal
chamber), scapula bone, flat bones of skull (parietal, frontal, lachrymal, temporal bone),
jaw bones.
3. Sesamoid bones
 These bones are developed by the ossification of tendons at the joints.
 Eg. Pisciform (wrist bone) of man and rabbit. One out of 8 carpals in man and 1 out of 9
carpals in rabbit.
Patella (knee bone): Largest sesamoid bone. Patella and two fabillae are present in rabbit.
4. Visceral bones
 Formed when ossification takes place in the visceral organs.
 Rare bones, found in few animals. In rabbit and man these bones are absent.
 Eg. Os cardis : Present in interventricular septum of deer’s heart.
Os palpebrae : In the eyelid of crocodile.
Os penis (Baculum) : In the penis of rodents rat, shrew, bat, whale, tiger.
Os rastralis : In the snout of pig.

37
TARGET POINTS
 Spongy bones: Bones in which Haversian systems are absent. Marrow cavity is present in the
form of trabeculae filled with RBM. All spongy bones are haemopoietic eg. ribs, pubis, sternum,
vertebrae, clavicle, end of long bones, scapula
 Compact bone: Haversian system is present eg. diaphysis of long bone.
 Diploic/Heterotypic: Middle part of bone is composed of spongy bone, in which trabeculae is
filled with RBM. While this bone is covered by compact bone on upper and lower surface eg. all
flat bones of skull.
 Pneumatic bone: In the matrix, air filled spaces are present so bone becomes light in weight eg.
bones of birds.
 Decalicified bone: If a bone is kept in dil HCl for 3 days then complete mineral part of the matrix
get dissolved in acid and organic part remain making the bone soft and flexible.
 Black bone: If a bone is dipped into conc. acid then outer surface of the bone gets burnt and it
appears black in colour.
 Dried bone: If a bone is kept in sunlight for long time then complete aqueous part of the bone
disappears. In these bones empty lacuna and empty bone marrow cavity is present. Shape of
bone remains unchanged.
If a bone is burnt or kept into very high temp then complete organic part of bone is burnt and
mineral part of matrix remain as such in the form of ash.
 Bright bone: If a bone is kept into KOH then complete attached muscle fibres dissolve in KOH
and bone becomes clear and bright called bright bone. Bone will remain unchanged eg. bones of
laboratory.
** Connective tissue vascular is described in detail in Module 8, Unit 3

38
1. White fibrous tissue is
a) Nervous b) Muscular
c) Ligaments d) Tendons
2. Loose connective tissue is
a) Areolar b) Bone
c) Blood d) Cartilage
3. Supportive connective tissue means
a) Tendon
b) Cartilage and bone
c) Ligament
d) Blood and lymph
4. Which of the following is an epidermal
structure of mammals?
a) Sebaceous gland
b) Receptors
c) Hair
d) Sweat gland
5. Assertion: Mucoid connective tissue is
called as embryonic tissue.
Reason: Mucoid connective tissue ismainly
found in embryonic stage.
a) A b) B
c) C d) D
6. Chondrin is composed of
a) Chondroitin-6-sulphate and osine
b) MAG and GA
c) Chondroitin-6-sulphateandhyaluronicacid
d) Chondroitin-6-sulphate and chondrocyte
7. Tendons and ligaments are a kind of
a) Muscular tissue
b) Connective tissue
c) Epidermal tissue
d) Nervous tissue
8. Elastin is found in
a) Yellow fibres of areolar tissue
b) Adipose tissue
c) Cartilage
d) Spongy bone
Simple Questions
9. Select the correctly matched pair.
a) Chondroblast - Matrix secreting
cells of cartilage
b) Elastic cartilage - Pubic symphysis
c) Fibrous cartilage - Pinna of ear
d) Hyaline cartilage - Intervertebral disc
10. The main function of ligament is
a) Joining of two bones
b) Joining of muscles
c) Joining of muscle to bone
d) Joining of muscle to nerves
11. Haversian canal contain
a) Blood vessels and nerves
b) Blood vessels only
c) Lymphatic only
d) Connective tissue only
12. Which cartilage is present on the end of long
bones?
a) Hyaline cartilage b) Fibrous cartilage
c) Calcified cartilage d) Elastic cartilage
13. Bone desolving cells
a) Osteoblast b) Osteocyte
c) Osteoclast d) Fibroblast
14. Assertion: Brown fat producesmore energy.
Reason: Brown fat is composed of
monolocular adipocyte.
a) A b) B
c) C d) D
15. Strongest cartilage is
a) White fibrous cartilage
b) Elastic cartilage
c) Hyaline cartilage
d) None
16. Epiglottis is composed of
a) Hyaline cartilage
b) Calcified cartilage
c) Both (a) and (b)
d) Elastic cartilage

39
17. Adipose tissue forms
a) Only during fetal development
b) Throughout life
c) Mainly during fetal development and the
first postpartum year
d) Mainly at puberty
18. Tissue (interstitial) fluid would most likely be
found in
a) Loose connective tissue
b) Nervous tissue
c) Adipose tissue
d) Bone tissue
19. Wharton jelly in umblical cord is
a) Mucoid connective tissue
b) Reticular connective tissue
c) Areolar connective tissue
d) Adipose connective tissue
20. Assertion: Mesenchymal cells are
undifferentiated cells of connective tissue.
Reason: Their function is formation of other
cells of connective tissue proper.
a) A b) B
c) C d) D
21. White adipose tissue contains
a) Multilocular fat cells
b) Bilocular fat cells
c) Unilocular fat cells
d) Alocular fat cells
22. Non-cellular layer that connects inner
surface of the epithelial tissue to the
connective tissue is
a) Endodermis
b) Cuticle
c) Connective tissue
d) Basement membrane
23. Tendons are made up of
a) Yellow fibrous connective tissue
b) Adipose tissue
c) Modified white fibrous tissue
d) Areolar tissue
24. Matrix of the connective tissue is secreted
by
a) Fibrocytes b) Histiocytes
c) Mast cells d) Plasma cells
25. Epithelia are involved in all the following
except
a) Protection b) Secretion
c) Connection d) Absorption
26. The hump of camel contains thick
concentration of
a) Areolar tissue b) Fibrous tissue
c) Adipose tissue d) Elastic tissue
27. A common character of tendon and ligament
is that both are made up of
a) Striated muscles
b) Connective tissue
c) Smooth muscles
d) Both (a) and (c)
28. Embryonic connective tissue is derived from
a) Ectoderm b) Endoderm
c) Mesoderm d) Mesogloea
29. Yellow fibres are present in
a) Bundles
b) Singly and branched
c) Singly and unbranched
d) None of these
30. Cartilage is
a) Nonvascular
b) Poorly vascular
c) Highly vascular
d) Irregularly vascular
31. Perichondrium is
a) Adipose tissue
b) White fibrous connective tissue
c) Yellow elastic tissue
d) Areolar connective tissue
32. Bone marrow is absent in
a) Reptilia b) Amphibia
c) Fishes d) Birds

40
33. Areolar tissue connects
a) The skin with muscles
b) Muscles to muscles
c) Bone to bone
d) Bone to muscles
34. Ligament is mainly made up of
a) Reticulin b) Elastin
c) Myosin d) Collagen
35. Regeneration of cartilage can occur from its
a) Matrix
b) Plasma
c) Perichondrium
d) A piece without perichondrium
Difficult Questions
1. Indentify the given below tissue with its type
and select the right option for the two
together
2. Alveoli has
a) Yellow fibrous connective tissue
b) White fibrous connective tissue
c) Areolar connective tissue
d) Adipose connective tissue
3. Eustachian tube is supported by
a) Elastic cartilage
b) White fibrous cartilage
c) Calcified cartilage
d) Hyaline cartilage
4. Identify the figure of animal tissue given
below along with it’s correct location :-
5. The covering of articular cartilage is made
up of
a) Areolar C.T.
b) Yellow fibrous C.T.
c) White fibrous C.T.
d) Reticular C.T.
6. Identify the animal, in which adipose tissue
excessively developed.
a) Desert rat
b) Bats
c) Whales
d) Beavers
Option
Tissue Type
a) Cartilage Specialised
connective tissue
b) Tendon Dense irregular
connective tissue
c) Ligament Dense regular
connective tissue
d) Bone Specialised
connective tissue
Tissue Location
a) Dense regular Heart
connective tissue
b) Dense irregular At bone joints
connective tissue
c) Adipose tissue Beneath skin
d) Areolar connective Beneath skin
tissue

41
7. Cartilage tissues are generally slow to heal
following an injury because
a) Cartilage is vascular in nature
b) Cartilage does not undergo mitosis
c) The matrix is semisolid
d) Chondrocytes are surrounded by fluids
8. Identify the type of connective tissue and
their components given in the figure.
A
B
C
D
a) A-White blood cells, B-Red blood cells,
C-Platelets, D-Blood
b) A-Haversian system, B-Central canal, C-
Lacuna, D-Bone
c) A-Macrophages, B-Collagenous fibre, C-
Elastic fibre, D-Loose connective tissue
d) A-Haversian system, B-Red blood cells,
C-White blood cells, D-Blood
9. Dermis of the skin is formed of
a) Plasma and RBC
b) Plasma and thrombocytes
c) Heparin and corpuscles
d) None of the above
10. Which of the statement is incorrect?
a) Cartilage contain chondrin which makes
the matrix
b) Matrix of bone is formed by ossein
c) Haversian canal system is characteristic
of mammalian bone
d) Volkmann’s canal connect the lacuna
present in the cartilage
11. Bones of old persons are brittle and fracture
more readily occur because they contain
more
a) Lacunae b) Organic matter
c) Inorganic matter d) Bone marrow
12. Our heart consists of
i) Epithelial tissue ii) Connective tissue
iii) Muscular tissue iv) Neural tissue
a) Only ii b) i and iii only
c) ii, iii and iv only d) All of these
13. What will happen if ligaments are cut or
broken?
a) Bones will move freely at joints
b) No movement at joint
c) Bone will become unfix
d) Bone will become fixed
14. Collagen and elastin are formed by
a) Macrophages b) Fibroblasts
c) Mast Cells d) Chondrocytes
15. Volkmann’s canals are found in
a) Bones of birds
b) Bones of amphilbians
c) Bones of mammals
d) Cartilage of mammals
16. Calcium phosphate is the principal chemical
constituent of
a) Mammalian bone b) Fibrous cartilage
c) Elastic cartilage d) Hyaline cartilage
17. Endoesteum is composed of
a) White fibrous C.T.
b) Reticular C.T.
c) Yellow fibrous C.T.
d) Areolar C.T.
18. Arzygophill fibres are present in
a) In spleen b) In tendons
c) In ligament d) In blood vessel
19. Collagen fibres are secreted by
a) Mast cells b) Macrophage
c) Histiocytes d) Fibroblasts
20. Ligament is
a) Modified white fibrous tissue
b) Inelastic white fibrous tissue
c) Modified elastic connective tissue
d) None of the above

42
21. Clavicle is
a) Membrane bone b) Cartilage bone
c) Visceral bone d) Sesamoid bone
ANSWER KEYS
Simple Questions
1.d 2.a 3.b 4.a 5.a 6.c 7.b 8.a 9.a 10.a 11.a 12.a
13.c 14.c 15.a 16.d 17.b 18.a 19.a 20.a 21.c 22.b 23.c 24.a
25.c 26.c 27.d 28.c 29.b 30.a 31.b 32.d 33.a 34.d 35.c
Difficult Questions
1.d 2.a 3.a 4.d 5.c 6.c 7.d 8.c 9.d 10.d 11.c 12.d
13.c 14.b 15.c 16.a 17.b 18.a 19.d 20.c 21.a 22. a
22. Difference between bone and cartilage is
a) Haversian canal b) Blood vessel
c) Lymph vessel d) None of these

43
1. Skeletal tissue originates from which
embryonic germinal layer?
a) Ectoderm b) Mesoderm
c) Endoderm d) All the above
2. Scavenger cell of connective tissue proper
is called as
a) Fibroblast cell b) Mast cell
c) Mesenchymal cell d) Macrophages
3. Bone forming cells are called
a) Osteoclast b) Osteoblast
c) Chondroblast d) Osteocyte
4. Hyaline cartilage is present at
a) The ends of digits
b) Tip of the nose
c) Epiglottis of mammals
d) Articular ends of long bones
5. Which of the following lacks blood supply?
a) Bone b) Connective tissue
c) Cartilage d) None of these
6. The inability to absorb digested nutrients
may be due to damage of which type of
epithelium?
a) Ciliated columnar
b) Simple columnar
c) Simple squamous
d) Simple cuboidal
DPP - 2
7. Septa which connects skin with underlaying
muscles are made up of
a) Epithelium tissue
b) Yellow fibrous C.T.
c) Adipose C.T.
d) Areolar C.T.
8. Which protein is present in largest amount
in human body?
a) Collagen b) Elastin
c) Albumin d) Keratin
9. Pigmented connective tissue is present in
a) Iris
b) Choroid
c) Frog’s skin (dermis)
d) All of the above
10. Which statement best describes the
connective tissue?
a) It isderived from endoderm and secretes
metabolic substances.
b) It is derived from mesoderm and
conducts impulses.
c) It is derived from mesoderm and
contains abundant matrix.
d) It is derived from ectoderm and is usually
layered.

44
UNIT 3 - INTEGUMENTARY SYSTEM
3.1 INTRODUCTION
Integumentary system is one of the main protective systems of the human body. It contains your
skin, hair, nails and several glands and so termed as integument.
3.1.1 Gross anatomy
Skin makes up approximately 7% of your body weight and is the largest organ in your body. It is also
known as your integument or covering.
Skin is made up of 2 mutually dependent layers that are distinguished based on their structure and
location. These layers – the epidermis and the dermis – contain a variety of structures, including
blood vessels, hair follicles, and sweat glands. Beneath the dermis lies the hypodermis (subcutis).
It is mainly composed of fatty tissues (loose connective – adipose and areolar). The hypodermis is
the “connection” layer. It connects the integument (epidermis and dermis) to organs and muscles in
the body.
Epidermis
Dermis
Hypodermis
3.1.2 Components
Epidermis (outer) – ectodermal in origin
Dermis (inner) – mesodermal in origin
Hair
Nail
Glands
Appendages
Skin
Skin is the most numerous component of the integumentary system.

45
The level of organization of the skin and its accessory structures are listed below:
• Molecular level – keratin, melanin and vitamin D.
• Microscopic level – Stem cells and skin cells.
• Tissue level – Epithelial and connective tissue.
• Organ level – Skin, consisting of the epidermis, dermis and hypodermis, as well as hair,
nails and glands.
A. Molecular level
i) Keratin
 A group of fibrous proteins that give hair, nails and skin their tough, water-resistant properties.
 Are filaments formed from the polymerization of intermediate filament proteins.
 In addition to intra and intermolecular hydrogen bonds, keratins have large amounts of the
sulfur containing amino acid cysteine, which forms disulfide bridges that confer additional
strength.
 Have an alpha-helix secondary structure in the central rod domain. Two keratin proteins then
come together and the helices wind around themselves to form a quaternary structure of a
coiled coil dimer. These dimers then assemble into protofilaments and then filaments.
-Helix
Coiled coil of two -helices

Protofilament (pair of coiled coils)
Filament (four right-hand twisted protofibrils)
ii) Melanin
 Melanin is a class of photopigment (“photo” meaning “light” and “pigment” meaning “colored
material”) with a molecular structure that allows it to absorb UV (ultraviolet) radiation from the
sun.
 Transforms the energy from the radiation into harmless heat, and melanin prevents the indirect
DNA damage from the sun that is responsible for many skin cancers.
 Melanin also gives skin, hair and eyes their color.

46
 Melanin is produced by specialty cells called melanocytes, inside special vesicles called
melanosomes. About 10 days after initial sun exposure, melanin synthesis peaks, which is
why pale – skinned individuals tend to suffer sunburns of the epidermis initially.
iii) Vitamin D
The epidermal layer of human skin synthesizes the precursor to vitamin D when exposed to UV
radiation. In the presence of sunlight, an isomer of vitamin D3
, cholecalciferol, is synthesized from a
derivative of the steroid cholesterol in the skin. The liver converts cholecalciferol to calcidiol, which
is then converted to calcitriol (the active chemical form of the vitamin) in the kidneys. Vitamin D,
which is really a hormone, is essential for normal absorption of calcium and phosphorus, which are
required for healthy bones.
In addition to affecting bone health, vitamin D is essential for general immunity against bacterial,
viral and fungal infections.
B. Microscopic level – Cells of the epidermis
The epidermis (or epithelial layer) is stratified squamous epithelia, composed of four to five layers
(depending on body region) of epithelial cells. The top layers of the epidermis are made up of:
i) Keratinocytes: These are cells containing the protein keratin. The keratinocytes on the most
superficial layer of the epidermis are dead, and periodically slough away, being replaced by cells
from the deeper layers. As keratinocytes move superficially from the deeper layers, they lose
cytoplasm and become flattened, allowing for many layers in a relatively small space.
Keratinocyte
Langerhans cell
Melanocyte
Merkel cell
Basal cells
Sensory neuron

47
ii) Basal cells: These cells are an example of tissue-specific stem cells, meaning they can turn
into a variety of cell types found in that tissue. Under normal conditions, daughter basal cells
most commonly replace lost keratinocytes.
The deepest layer of the epidermis and the most superficial layer of the dermis give out projections
that interlock with each other (like Velcro) and strengthen the bond between the epidermis and
the dermis. The projections originating in epithelial cells of the bottom layer of the epidermis are
called desmosomes, and the ones originating in the dermis are called dermal papillae. Think
of the projections as a formation of folds of cellular matter. The greater the fold, the stronger the
connections made.
iii) Merkel cells: These are sensory receptors that detect light touch. They form synaptic connections
with sensory nerves that carry touch information to the brain. These cells are abundant on the
surface of the hands and feet.
iv) Melanocytes: These are the cells in the bottom layer of epidermis that produce the pigment
melanin, which gives hair and skin itscolor. Individualswhose melanocytes produce more melanin
have darker skin color. Cellular extensions of the melanocytes reach up in between the
keratinocytes.
(v) Dendritic or Langerhans cells: These are tissue macrophages that contribute to the immune
function of the skin. They engulf foreign organisms and signal to the immune system. Since the
skin is in constant contact with the environment, it is important to have immune cells to help
destroy any pathogens that might get pass the cell barrier of the epidermis.
C. Tissue level
The skin contains many tissue types. The epidermis is classified as epithelial tissue composed of
stratified squamous epithelia. The dermis is made of different types of connective tissues including
areolar and dense irregular connective tissue, and histiocytes (tissue macrophages). The hypodermis
contains areolar connective tissue, adipose tissue, and glands.
i) Epithelial tissue:The epidermisis mainly made up of stratified (layered) squamous (flat) epithelial
cells. Epithelial cells found in the different layers of the epidermis have different shapes.
Stratification (layering) is important in the epithelial tissue of the integumentary system, which
forms a barrier. Epithelial cells found in other systems have other surface cell shapes, including
cube like (cuboid) and column like (columnar) in a single layer (simple) or multiple cell layers
(stratified).
ii) Connective tissue: While the epidermis is composed of epithelial cells, the dermis is composed
of connective tissue. The dermis connects the epidermis to the hypodermis and provides structure
and elasticity from collagen and elastin fibers. These proteins are made by fibroblasts found in
the dermis. Collagen and elastin work together. Collagen provides strength; elastin, as the name
implies, is elastic and allow for distension. The skin must remain strong to protect you from

48
abrasions and other cuts. However, the skin also needs to be able to deform and hopefully,
return to its original shape.
TARGET POINTS
Body wall – It is thicker than integument and consists of many layers:
 Integument
 Panniculus adiposus: Layer of adipose connective tissue.
 Tela subcutanea: Layer of areolar connective tissue.
 Panniculus carnosus: Layer of skeletal muscles.
 Parietal peritoneum: Inner lining of body wall composed of simple squamous epithelium. All
layers of body wall are mesodermal in origin except epidermis which is ectodermal in origin. So
complete body wall is ectomesodermal in origin.
3.2 SKIN STRUCTURE
Complete skin is ectomesodermal in origin. Study of skin is called Dermatology.
Meissner`s corpuscle
Free nerve ending
Reticular layer of dermis
Sebaceous (oil) gland
Arrector pili muscle
Sensory nerve fibre
Eccrine sweat gland
Pacinian corpuscle
Epidermis
Dermis
Hypodermis
(superficial)
fascia)
Hair root
Hair follicle
Eccrine sweat gland
Hair shaft
Pore
Dermal papillae
(papillary layer of derm)
Hair follicle receptor
(root hair plexus)
Adipose tissue
Artery
Vein

49
3.2.1 Epidermis
The epidermis (or epithelial layer) is made up of four or five distinct layers (strata), depending on the
region of the body. From deep to superficial, they are named the stratum basale, stratum spinosum,
stratum granulosum, stratum lucidum, and stratum corneum. The stratum lucidum is unique to
areas like the palms of the hand (palmar surfaces) and soles of the feet (plantar surfaces), where the
skin is thicker than it is in the rest of the body. The stratum basale is made up of the many cell types
already discussed, including basal cells, melanocytes, Langerhans cells and Merkel cells. As you look
at the more superficial layers, you see that they become mostly (or completely) composed of
keratinocytes, which protect and waterproof the body. As the cells are pushed superficially (toward the
surface) they make keratin. As the cells begin to fill with keratin, they become increasingly impervious
to water, and it becomes more difficult for osmosis and diffusion to occur inside the cell. In addition, as
cells enter each superficial layer (further away from the dermis, which contains the blood supply), the
distance across which oxygen and other nutrients must diffuse increases, making it harder for the
cells to get the nutrients they need. The keratinocytes in the stratum corneum (the most superficial
layer) are usually inert, or dead and periodically slough away, being replaced by cells from the deeper
layers.
The five strata of epidermis are as follows:
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
Dermis
A. Stratum basale
The stratum basale (also called stratum germinativum) is the deepest epidermal layer and attaches
the epidermis to the basal lamina, below which lie the layers of the dermis. The stratum basale is

50
primarily made up of a single layer of basal cells (cuboidal or columnar in shape). These cells are
considered to be stem cells. The function of this layer is to divide to replicate the cells that are lost
from the surface. The daughter cells then differentiate into keratinocytes. Merkel cells and
melanocytes are also dispersed among the basal cells in the stratum basale.
B. M. dermis
Keratinocytes
Melanosome
Melanocytes
Melanoblast
B. Stratum spinosum
As the name suggests, the stratum spinosum is spiny in appearance due to the polyhedral shape of
the cells and desmosomes visible. As basal cells divide at different rates, keratinocytes get pushed
up but maintain these strong cell to cell connections, changing cell shapes and forming a protective
barrier. This stratum is composed of eight to 10 layers of keratinocytes, formed as a result of cell
division in the stratum basale. Interspersed among the keratinocytes of this layer are the Langerhans
cells, which help with immunity.
C. Stratum granulosum
The stratum granulosum has a grainy appearance due to further changes to the keratinocytes as
they move up from the stratum spinosum. The cells (three to five layers deep) become flatter, and
their cell membranes thicken. At this point, the keratinocytes generate large amount of protein
keratin and keratohyalin in the cytoplasm and, with other lipids and enzymes, form vesicles called
lamellar granules, which may be secreted by exocytosis. The cellular secretions act to retard water
loss and entry of foreign materials. These two proteins eventually make up the entire mass of the
keratinocytes in the stratum granulosum ( the nuclei and other cell organelle disintegrate) and mark
the transition between the metabolically active strata and the dead cells of the superficial strata.
Keratohyalin granules are composed of Ca2+
, acidic polysaccharides and RNA. Stratum granulosum
can be stained by hematoxylin. Glycogen granules are also present in their cytoplasm in little amount.
Keratohyaline
Ca
Acidic
RNA
polysaccharide

51
D. Stratum lucidum
The stratum lucidum appears lucid, or clear, and is not present throughout the body, but only on
parts with thick skin, such as the surface of the palms and the soles of the feet. The stratum lucidum
is a smooth, thin layer, just superficial to the stratum granulosum. The keratinocytes in this layer are
derived from the stratum granulosum, and mainly consist of keratin fibers. They are flat and densely
packed. Cells are in 2 – 4 layers and are rectangular in shape. Eleidin, a waterproof protein is
present which makes this layer waterproof and thus, it acts as a barrier layer.
E. Stratum corneum
The stratum corneum is the most superficial layer of the epidermis, and is the layer that is exposed
to the environment. The increased keratinization (also called “cornification”) of the cells in this
layer gives it its name. There are usually 15 to 30 layers of dead cells in the stratum corneum. This
dry, dead layer prevents the growth of microbes and keeps the rest of the underlying layers healthy.
It is also resistant to penetration by water and protects the inner layers from environmental damage.
Dead cells in this layer are shed periodically (approximately every two weeks) and are replaced by
cells from the stratum granulosum (or stratum lucidum in the case of the palms and soles).
The shedding of keratin is called ecdysis / moulting. Few living cells (< 1% present) are endocrine
in nature and secrete unknown hormones that control and regulate the division of stratum basale.
TARGET POINTS
 Thickest stratum corneum is seen on sole and palm.
 Thinnest stratum corneum on lips.
 Thinnest epidermis is seen on conjunctiva of eye.
 Thickest epidermis is seen on sole and palm.
 Sloughing: Periodic shedding of intact stratum corneum in snakes
 Keratin scales which falls from epidermis in frog are composed of simple squamous epithelium
in which cells are nucleated and living.
3.2.2 Dermis
The skin’s dermis is made up of two distinct layers of connective tissue. The papillary layer is
made up of areolar connective tissue and the underlying reticular layer is composed of dense
irregular connective tissue. This dermal part of the skin (organ) is vasculated (has blood vessels)
and is innervated (has nerves). The dermis is sparsely populated with fibroblasts that produce
collagen and elastin fibers in the extracellular matrix. This leads to a strong and elastic tissue
structure. The matrix can also contain mast cells involved in allergic reactions.
A. Papillary layer (Pars papillaris)
The fibroblasts are dispersed within the collagen and elastin fibers of the areolar tissue (loose
connective tissue) of the papillary layer. This forms a loose mat, which contains an abundance of
small blood vessels. The dermal papillae with blood capillaries interdigitate (become interlocked)
with the epidermal ridges of the stratum basale. In addition, the papillary layer contains phagocytes

52
– defensive cells that help fight bacteria or other infections that have breached the skin. This layer
is also interspersed with lymph vessels and sensory receptors.
B. Reticular layer (Pars reticularis)
The reticular layer appears “reticulated”(net like) because it is composed of a mesh of collagen
fibers and elastin fibers. Fibrocytes form the bundles of collagen that extend into the papillary layer
and the hypodermis, making these layers hard to distinguish. The flexible collagen provides structure
and strength, while elastin lends limited elasticity to the skin. Collagen also binds with water, keeping
the skin hydrated. Water is necessary to maintain the normal elasticity and resiliency (called “turgor”)
of the skin. Dehydration causes a loss of turgor; if the skin of a dehydrated person is pinched, it
remains domed and does not immediately flatten out.
Fibroblast, mast cell and macrophage are more in numbers. Matrix composed of mucopolysaccharide.
TARGET POINTS
 Dermis is mesodermal in origin, derived embryologically from dermatome.
 Dermis is 2 or 3 times thicker than epidermis.
 Tanning: Preservation of dermis to obtain leather
 Taxidermy: Preservation of whole skin with its derivatves
 Rete pegs: Invagination of epidermis into dermis in the form of grooves. Dermal papilla and rete
pegs make the dermal epidermal junction provide rigidity to complete skin.
 In the dermis of frog, two regions (i) spongiosum layer (outer) and (ii) compactum layer (inner)
are present.
3.2.3 Hypodermis
The hypodermis is made up of areolar tissue, collagen, and elastic fibers, providing it with some
elasticity. Additionally, it contains adipose tissue, which functions as a mode of fat storage. The
hypodermis is vascular and contains arteries, veins and blood capillaries.
Adipose tissue present in the hypodermis accumulates fat, which serves as an energy reserve,
insulates the body, and prevents heat loss. The fat distribution changes as our bodies mature and
age. It is also hormone dependent. Men tend to accumulate fat in different areas (neck, arms, lower
back, and abdomen) than do women (breasts, hips, thighs, and buttocks). Improved diet and
increased exercise are the best ways to control body fat accumulation, especially when it gets to
levels that increase the risk of heart disease.

53
3.2.4 Cutaneous receptors
Merkel`s disk
(touch)
Krause`s
corpuscles
(cold receptors)
Sebaceous
gland
Hair
folicle
receptor
Arrector
pili muscles
Ruffini`s
corpuscle
(touch, pressure)
Sweat
gland
Meissner`s
corpuscle
(sensitive touch)
Pacinian
corpuscle
(pressure)
Blood
vessels
Free nerve
ending
Structure and location of cutaneous receptors
A. Algesireceptors: These are sensitive towards pain; found only in the form of naked nerve-
fibers (max. 40 lakh in man). These types of receptors are maximum in number.
B. Tangoreceptors: These are sensitive towards touch. Many type of corpuscles sensitive to
touch are found in skin.
i) Meissener’s corpuscles: Found in the dermal-papilla i.e., located in the outer part of
dermis. These are more in number in the skin of lips, finger-tips, nipples.
ii) Genital corpuscles: Meissener’s corpuscles which are present in the skin of external
genital organs like clitoris and glans penis are termed as genital-corpuscles.
iii) Merkel’s disc: Their upper part extends in the epidermis and their basal part is present in
the dermis.
iv) Pacinian corpuscles: Placed deep into the dermis and are sensitive to pressure.

54
C. Thermoreceptors: These are of 2 types:
i) End bulb of Krause: These are bulb-shaped corpuscles, sensitive to low-temperature.
These are frigidoreceptors.
ii) End organ of Ruffini: These are long and spiral corpuscles, sensitive to high temperature.
These are caloreceptors.
D. Vibroreceptors: In rabbit, these are vibrissae or Whiskers. They are sensitive to vibrations
and are also responsible for directional movement and touch.
3.3 SKIN ACCESSORY STRUCTURES
Accessory structures of the skin include hair, nails, sweat glands and sebaceous glands. Although
these structures appear to be part of the dermis, they are actually derived from the epidermis. The
hair shaft is made of dead, keratinized cells and gets its color from melanin pigments. Nails are also
keratinized and protect the extremities of our fingers and toes from mechanical damage. Sweat
glands and sebaceous glands produce sweat and sebum, respectively. Each of these fluids has a
role to play in maintaining homeostasis. Sweat helps the body remove excess fluids and electrolyte
wastes and also cools down the body surface when it gets overheated. Sebum act as a natural
moisturizer of the dead, flaky outer keratin layer of skin and hair. Sebum is also known for its
microbicidal and microbiostatic properties.
3.3.1 Hair
Adipose tissue
Hair shaft
Epidermis
Dermis
Eccrine
sweat gland
Subcutaneous
(hypodermis)
Dermal papilla
Sebaceous gland
Pacini corpuscle
Arrector pili muscle
Strands of hair originate from the base of the downward extension of living epithelial cells into the
dermis that is called the hair follicle. Hair follicles are surrounded by the dermis, but the cells are
part of the epidermis and are separated from the dermis by basal lamina layer. Hair forms in a
manner similar to the skin: rapid division and differentiation of stem cells into keratinocytes that get

55
pushed up and become flattened, dead, keratinized cells. The part of hair that is exposed on the
skin surface is called the hair shaft, and the rest of the follicle is called the hair root. The bulge at
the base of the hair root is called the hair bulb, which is made up of a layer of basal cells called the
hair matrix. The hair matrix contains the cells that rapidly divide to form the hair. The hair bulb
surrounds the hair papilla (made up of connective tissue, blood capillaries and nerve endings).
Basal cells in the center of the hair bulb divide to form layers of keratinocytes that form the medulla,
cortex and cuticle of the hair bulb. Keratin formation starts in the cells of the medulla and the
keratin continues to be produced in the cortex and cuticle. Keratinization is completed as the cells
are pushed to the skin surface to form the shaft of hair that is externally visible. The external hair is
composed entirely of keratin.
Additionally, the hair follicle is made up of three concentric layers that make up the wall of the follicle
– the internal root sheath, the external root sheath, and the glassy membrane. The cells of the
internal root sheath are derived from the basal cells of the hair matrix. This layer does not surround
the entire hair strand, but stops short at the base of the hair shaft. The external root sheath, which
encloses the hair root, is made up of basal cells at the base of the hair root and tends to be more
keratinous in the upper regions. The glassy membrane is a thick, clear connective tissue sheath
covering the hair root and connecting it to the tissue of the dermis.
Hair serves a variety of functions. Hair on the head protects it from the sun and from heat loss; and
hair in the nose and ears and around the eyes (eyelashes) defends the body by trapping dust
particles that may contain allergens and microbes. Hair on the eyebrows prevents sweat and other
particles from bothering the eyes. Hair also has a sensory function due to innervation of the hair
papilla. Hair is extremely sensitive to changes in the environment; much more so than the skin
surface. The hair root is connected to smooth muscles called arrector pili that contract in response
to stimuli, making the external hair shaft “stand up”. This is visble in humans as goose bumps and
even more obvious in animals, such as when a frightened cat’s fur puffs out.
3.3.2 Nails
Stratum corneum
Nail root
Free edge
Nail body
Lunula
Nail root
Cuticle
Nail body
Eponychium
Hyponychium

56
The nail is a specialized structure of the epidermis that occurs at the tips of our fingers and toes.
The nail body is formed on the nail bed, and it is designed to protect the tips of our fingers and
toes, as they are the farthest extremities and the parts of the body that experience the maximum
mechanical stress. The epidermis in this part of the body has evolved a specialized structure upon
which nails can form. The nail body forms at the nail root. Lateral nail folds, folds of skin that
overlap the nail on its side, help anchor the nail body. The nail fold that meets the proximal end of the
nail body forms the nail cuticle, also called the eponychium. The nail bed is rich in blood vessels,
making it appear pink, except at the base, where there is a crescent shaped region called the
lunula. The nail body is composed of keratin rich, densely packed dead keratinocytes. The area
beneath the free edge of the nail, where debris gets lodged, is called the hyponychium.
3.3.3 Cutaneous glands
Cutaneous glands are ectodermal in origin. Sweat gland and sebaceous glands are main cutaneous
glands and rest glands are modification of these glands.
A. Sweat glands
 Main function is thermoregulation.
 These are coiled tubular in structure. Coiled part of this gland is called secretory unit, around
secretory unit myoepithelial cells are present. When they contract sweat comes out from
this gland. Sweat is like dilute urine.
 In sweat more than 99% is water and in rest part urea, uric acid, ammonium chloride and
sodium chloride salts are present. Lysozyme is also present which destroy bacteria.
 Smell in sweat due to presence of fatty substances, which are decomposed by bacteria.
 Sweat glands are of two types:
i) Eccrine or merocrine: Secrete sweat by simple diffusion so their secretion is like watery
liquid. Eg. maximum sweat gland of human body, in rabbit, these are found on paws.
ii) Apocrine: In their secretion little part of cytoplasm of gland or part of gland itself is present
so their secretion is concentrated. Due to presence of pigment, sweat of these glands is
pale yellow in colour. Its common sites of presence are:
Human: In armpits, in pubic region, skin around lips, nipples (areolar region: Areola
mammae), skin around anus.
Rabbit: On lips, skin around lips
B. Sebaceous/Oil glands
 Simple branched alveolar in structure.
 Holocrine in nature (complete cytoplasm is destroyed).
 Found in attached position with the lateral surface of hair follicle. In few body parts they are
present in the absence of hair follicle, like lips, nipples, glans penis and clitoris. These glands
are completely absent in sole and palm. They are maximum on forehead and face.
 In whale and seal (aquatic mammals) sebaceous glands are completely absent.

57
 Their secretion is called sebum. In composition, all fatty substances are present like ester,
cholesterol, phospholipids and triglycerides. Ester and cholesterol are converted into vitamin
D in presence of sunlight.
C. Mammary gland
 In eutherians, mammary glands are modifications of apocrine sweat glands thus, their secretion
is concentrated. Active mammary glands are found in females while in males they are present
in inactive form.
 In prototherians, mammary glands are modifications of sebaceous glands thus, their secretion
is thick and sticky (semi–solid). Both male and female have active mammary glands. This
condition is called Gynaecomastism. Nipples are absent and sticky milk is collected in two
shallow pits which are present on abdominal skin.
 Active mammary glands are compound tubulo alveolar in structure. Inactive mammary glands
are compound tubular in structure.
 Secretion: Milk composed of lactoalbumin, lacto globulin, lactose sugar, casein
(phosphoprotein), fats, calcium. IgA secretory antibody is present. Iron and vitamin - C are
absent in milk.
 Control of mammary glands:
Alveolar growth  Progesterone
Tubular growth  Oestrogen
Ejection of milk  Oxytocin (milk let down hormone)
Synthesis of milk  Prolactin
D. Ceruminous glands
 Modified sweat glands, found in external auditory canal (meatus).
 Secretory duct opens in hair follicle of auditory canal.
 Watery secretion of ceruminous glands makes cerumen or ear wax with the secretion of
sebaceous glands attached with the hair follicle.
 Function of cerumen: Prevent growth of bacteria and prevent the entry of insects and dust
particles in auditory canal and protect ear drum.
E. Perineal glands
 Modified apocrine sweat glands or sebaceous glands (for rabbit  sebaceous).
 Found in rabbit and absent in human.
 Found in the skin of external reproductive organs and skin around anus.
 Their secretion is milky white in which specific smell is present. Due to smell in their secretion
these glands are called as scent–glands.
 Function: Help in sexual attraction.

58
F. Moll’s glands
 These are modifications of sweat glands.
 Found in eye lids.
 Secretory duct opens in the hair follicle of eye lashes.
 Moll’s gland acts with zeis glands which are attached with the hair follicle of eye lashes.
Secretion of both these glands make eye lashes and skin around eye lashes moist and oily.
G. Zeis glands
 Modified sebaceous glands, attached with the hair follicles of eye lashes.
 Oily secretion acts with watery secretion of moll’s glands and makes the skin around eye–
lashes moist and oily.
H. Meibomian glands
 Modified sebaceous glands, found in eye lids.
 Secretory duct opens in corner of eye. Oily secretion makes oily layer on the layer of tears on
the conjunctiva of eye, so tears do not fall. Tears are essential for the protection of living cells
of conjunctiva.
TARGET POINTS
 In kangaroos, hippopotamus and monkey, colour of sweat is red.
 Dog, shrew, whale mammals have no sweat glands.
 Maximum sweat glands are found on sole and palm.
 Sweat glands are absent on lips, nipples, glans penis and clitoris.
3.4 SKIN FUNCTIONS
A. Protection (primary function)
Skin makes the first line of defence because
a) Most cells of outermost layer of skin are dead.
b) Lysozymes present in sweat destroy bacteria.
c) pH of skin is highly acidic (3 - 5) so bacteria are unable to grow.
B. Respiration (in frog)
Frog cannot live without cutaneous respiration. During hibernation frog respires only through skin.
Mucous glands make skin moist. These glands are multicellular.
Mammalian skin does not help in respiration due to absence of mucous glands.
C. Excretion: Urea, uric acid, NH4
Cl.
D. Absorption: Creams, oil

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