B.Pharm-Ist sem-HAP-Chapter 3-tissue level of organization.pptx

Miss. Sheetal Patil M. Pharm
Rani Chennamma College Of Pharmacy,
Belagavi

Introduction
 The term tissue is used to describe a group of cells found together in the
body. The cells within a tissue share a common embryonic origin. Function
together to carry out specialized activities.
 Histology is the science that deals with the study of tissues.
 Pathologist specialized in laboratory studies of cells and tissue for diagnoses.

 Types of tissues
On the basis of structure and functions body tissues are classified into four
types:
1. Epithelial tissue
• Covers body surfaces and lines hollow organs, body cavities, duct, and forms glands.
2. Connective tissue
• Protects, supports and binds organs.
• Stores energy as fat, provides immunity.
3. Muscular tissue
• Generates the physical force needed to make body structures move and generate body
heat.
4. Nervous tissue
• Detect changes in body and responds by generating nerve impulses.

 Development of Tissues
 Tissues of the body develop from three primary germ layers:
Ectoderm, Endoderm and Mesoderm
 Epithelial tissues develop from all three germ layers.
 All connective tissue and most muscle tissues form from mesoderm.
 Nervous tissue develops from ectoderm.

 Epithelial cell
 Epithelial tissue consists of cells arranged in continuous sheets, in either
single or multiple layers.
 Closely packed and held tightly together.

 General Features of Epithelial Cells
 Surfaces of epithelial cells differ in structure and have specialized functions
i. Apical (free) surface
 Faces the body surface, body cavity, lumen, or duct
ii. Lateral surfaces
 Faces adjacent cells
iii. Basal surface
 Opposite of apical layer and adhere to extracellular materials

 General Features of Epithelial Cells
1. Basement membrane
 Thin double extracellular layer that serves as the point of attachment and
support for overlying epithelial tissue
a. Basal lamina
 Closer to and secreted by the epithelial cells
 Contains laminin, collagen, glycoproteins, and proteoglycans
b. Reticular lamina
 Closer to the underlying connective tissue
 Contains collagen secreted by the connective tissue cells

1. Epithelial Tissues
 Epithelial tissues are essentially large sheets of cells covering all the surfaces of
the body exposed to the outside world and lining the outside of organs.
 Epithelium also forms much of the glandular tissue of the body.
 Epithelial tissues are nearly completely avascular. No blood vessels cross the
basement membrane to enter the tissue, and nutrients must come by diffusion or
absorption from underlying tissues or the surface.
 Has nerve supply.
 Apical, lateral and basal surfaces of epithelial cells are modified in various ways
to carry out specific functions.
 Epithelial tissues are capable of rapidly replacing damaged and dead cells.

 Classification of epithelial tissues
 Epithelial tissues are classified according to :
 Number of the cell layers formed
I. Simple epithelium (one layer)
II. Stratified epithelium(several layer)
 The shape of the cells
I. Squamous (flat cell)
II. Cuboidal (cube like)
III. Columnar (rectangular)
IV. Transitional (variable)

 Covering and Lining Epithelium
 Arrangement of cells in layers
 Consist of one or more layers depending on function
a. Simple epithelium
 Single layer of cells that function in diffusion, osmosis, filtration, secretion, or
absorption.
b. Pseudostratified epithelium
 Appear to have multiple layers because cell nuclei at different levels
 All cells do not reach the apical surface
c. Stratified epithelium
 Two or more layers of cells that protect underlying tissues in areas of wear and
tear

 Different Types of Covering and Lining Epithelium
 Cells vary in shape depending on their function
a. Squamous
 Thin cells, arranged like floor tiles.
 Allows for rapid passage of substances.
b. Cuboidal
 As tall as they are wide, shaped like cubes or hexagons.
 May have microvilli .
 Function in secretion or absorption.

c. Columnar
 Much taller than they are wide, like columns
 May have cilia or microvilli
 Specialized function for secretion and absorption
d. Transitional
 Cells change shape, transition for flat to cuboidal
 Organs such as urinary bladder stretch to larger size and collapse to a smaller
size

A. Simple Epithelium
i. Squamous epithelium
ii. Simple cuboidal epithelium
iii. Simple columnar epithelium (nonciliated and ciliated)
iv. Pseudostratified columnar epithelium (nonciliated and cilated)

i. Simple squamous epithelium
 Single layer of flat cells having centrally located nucleus.
 Location: It lines heart, blood vessels, lymphatic vessels, air sacs of lungs,
glomerular capsule.
 Function
 Filtration (e.g., kidneys)
 Diffusion (e.g., oxygen in lungs)
 Osmosis
 Secretion

ii. Simple Cuboidal Epithelium
 It consist of single layer of cube shaped cells having centrally located
nucleus.
 Location: It found in ovary, lines of kidney tubules,thyroid gland and the
ducts of some glands, (e.g., the pancreas)
 Function
 It has the function of secretion and absorption

iii. Nonciliated Simple Columnar Epithelium
 It consist of single layer of of nonciliated column like cells with nuclei near
base of cell.
 It contains goblet cells and cells with microvilli in some location.
 Location: It lines gastrointestinal tract, ducts of many glands and gall
bladder.
 Function
 It has function of secretion and absorption.

iv. Ciliated Simple Columnar Epithelium
 It consist of single layer of ciliated column like cells with nuclei near base,
contains goblet cells in some locations.
 Location: Lines few portion of upper respiratory tract, uterine tubes, uterus,
ventricles of brain.
 Function
 Moves mucus and other substances by ciliary action.

v. Pseudostratified columnar epithelium
 Appears to have several layers due to nuclei are various depths
 All cells are attached to the basement membrane in a single layer but some
do not extend to the apical surface.
 Location: It lines the airways of most of the upper respiratory tract, larger
ducts of many gland etc.
 Function
 Secretion and movement of mucus by ciliary action.

B. Stratified Epithelium
 Two or more layers of cells.
 Specific kind of stratified epithelium depends on the shape of cells in the
apical layer.
i. Stratified squamous epithelium
ii. Stratified cuboidal epithelium
iii. Stratified columunar epithelium
iv. Transitional epithelium

i. Stratified Squamous Epithelium
 Several layers of cells that are flat in the apical layer.
 New cells are pushed up toward apical layer.
 As cells move further from the blood supply they dehydrate, harden, and die
 Location: Keratinized form contain the fibrous protein keratin, found in
superficial layers of the skin, nonkeratinized form does not contain keratin,
found in mouth, pharynx, esophagus, tongue and vagina.
 Function
 Protection and limited secretion.

ii. Stratified Cuboidal Epithelium
 It consist of two or morw layers of cells in which cells in the apical layer are
cube shaped.
 Location: Ducts of sweat glands, and part of oesophageal glands and part of
male urethra.
 Functions
 Protection and limited secretion and absorption.

iii. Stratified Columnar Epithelium
 It consist of several layers of irregularly shaped cells, only apical layer has
columnar cells.
 Location: lines part of urethra, oesophageal glands, and part of conjuctiva of
the eye
 Functions
 Protection and secretion

iv. Transitional Epithelium
 Its appearance is variable, shape of cells in apical layer ranges from
squamous to cuboidal.
 Location: Lines urinary bladder and portion of ureter and urethra.
 Functions
 Permits distention.

 Glandular Epithelium and Glands
There are main two types of glands
1. Endocrine Glands
2. Exocrine Glands
 Glands
 Glands secret substances in ducts, called hormones, diffuse directly into the
bloodstream.
 Function in maintaining homeostasis.

2. Endocrine Glands
 Their secretory products (hormones) diffuse into blood after passing through
interstitial fluid.
 Location: pituitary gland, pineal, thyroid, parathyroid, adrenal thymus,
pancreas, ovaries, testes etc.
 Functions
 Produces hormones that regulate various body activities

2. Exocrine Glands
 Their secretory products are released into ducts.
 Location: Sweat, oil and ear wax glands of the skin, digestive glands like
salivary glands which secrete into mouth, pancreas which secrete into small
intestine.
 Functions
 Produces substances such as sweat, oil, earwax, saliva or digestive enzymes.

 Structural Classification of Exocrine Glands
They are classified according to whether their duct is branched or not.
1. Simple gland
2. Compound gland
 A simple gland has an unbranched duct (or no duct at all). There is only a
single secretory unit (acinus or tubule). Examples include sweat
glands, gastric glands, intestinal crypts and uterine glands.
 A compound gland has a branching duct. Salivary glands and pancreas are
examples. They are typically fairly bulky and contain many individual
secretory units (acini or tubules).

1. Simple glands
i. Simple tubular
ii. Simple branched tubular
iii. Simple coiled tubular
iv. Simple acinar
v. Simple branched acinar
2. Compound glands
i. Compound tubular
ii. Compound acinar
iii. Compound tubuloacinar

1. Simple glands
i. Simple tubular
 Tubular secretory part in straight and attaches to a single unbranched duct.
 E.g., glands in large intestine
ii. Simple branched tubular
 Tubular secretory part is branched and attaches to a single unbranched
ducts.
 E.g., gastric glands

iii. Simple coiled tubular
 Tubular secretory part is coiled and attaches to a single unbranched duct.
 E.g., sweat glands
iv. Simple acinar
 Secretory partion is rounded and attaches to a single unbranched duct.
 E.g., glands of the urethra
v. Simple branched acinar
 Rounded secretory part is branched and attaches to a single unbranched
ducts.
 E.g., sebaceous glands

1. Compound glands
i. Compound tubular
 Secretory portion is tubular and attaches to branched ducts
 E.g., bulbourethral glands
ii. Compound acinar
 Secretory portion is rounded and attaches to branched duct.
 e.g., mammary glands
iii. Compound tubuloacinar
 Secretory portion is both tubular and rounded and attaches to a branched ducts.
 e.g., acinar glands of the pancreas

 Functional Classification of Exocrine Glands
1. Merocrine glands
2. Aprocrine glands
3. Holocrine glands

Functional Classification of Exocrine Glands

2. Connective Tissue
 Most abundant and widely distributed tissues in the body.
 Functions of connective tissues
i. Binds tissues together
ii. Supports and strengthen tissue
iii. Protects and insulates internal organs
iv. Compartmentalize and transport
v. Energy reserves and immune responses

Cells and fibres of connective tissues

 Characteristics of Connective Tissue
 Extra cellular matrix
 Fibers
 Cells of various types

 Extracellular matrix of Connective Tissue
 Extracellular matrix is the material located between the cells.
 Consist of protein fibers and ground substance.
 Connective tissue is highly vascular.
 Supplied with nerves.
 Exception is cartilage and tendon. Both have little or no blood supply and no
nerves.

 Connective Tissue Cells
i. Fibroblasts
 Secrete fibers and components of ground substance of extracellular matrix
(ECM).
ii. Adipocytes (fat cells)
 Store triglycerides (fat), found deep to the skin and around organs such as
heart and kidney.
iii. Mast cells
 Produce histamine, also ingest and kill bacteria. Abundant alongside blood
vessels.

iv. White blood cells
 Have role in immune response. They migrate from blood into connective
tissue in response to certain conditions. E.g., neutrophils gather at sites of
infection.
v. Macrophages
 A type of WBC. They engulf bacteria and cellular debris by phagocytosis.
vi. Plasma cells
 Develop from B lymphocytes and secrete antibodies. They are an important
part of body’s immune response.

 Connective Tissue Extracellular Matrix
 Ground substance and fibres make up the ECM.
a) Ground substance
 Between cells and fibers.
 Functions to support and bind cells, store water, and allow exchange between
blood and cells.
 Complex combination of proteins and polysaccharides (hyaluronic acid,
chondroitin sulphate dermatan sulphate and keratan sulphate).

b) Fibres
i. Collagen fibers: Composed of collagen protein, found in bone, tendons
and ligaments. They are very strong, resist pulling forces and flexibility of
the tissues.
ii. Elastic fibers: Composed of elastin, glycoproteins. Found in skin, blood
vessels and lungs. They join together to form network within a tissue. They
show elasticity.
iii. Reticular fibers: Composed of collagen and glycoproteins. Found around
fat cells, nerve fibres, skeletal and smooth muscle cells. They provide
support and strength.

 Classification of Connective Tissues
A. Embryonic connective tissue
I. Mesenchyme
II. Mucous connective tissue
B. Mature connective tissue
I. Loose connective tissue
a. Areolar connective tissue
b. Adipose tissue
c. Reticular connective tissue
II. Dense connective tissue
a. Dense regular connective tissue
b. Dense irregular connective tissue
c. Elastic connective tissue
III. Cartilage
a. Hyaline cartilage
b. Fibrocartilage
c. Elastic cartilage
IV. Bone tissue
V. Liquid connective tissue
a. Blood
b. Lymph

A. Embryonic Connective Tissue
I. Mesenchyme
 Consist of irregularly shaped mesenchymal cells embedded in a semiflui
ground substances that contains reticular fibres.
 Location: Under skin and along developing bones of embryos and along
blood vessels.
 Functions
 Forms all other types of connective tissues.

II. Mucous connective tissue (Wharton’s jelly)
 Consist of widely scattered fibroblast embedded in viscous substances that
contains collagen fibres.
 Location: umbilical cord of fetus.
 Functions
 Support

B. Mature connective tissue
I Loose Connective Tissue
a. Areolar Connective Tissue
 It consist of fibres (collagen, elastic and reticular) and cells (fibroblast,
macrophages, mast cells, plasma cells) embedded in semifluid ground
substances.
 Location: deep to skin, around blood vessels, nerves and body organs.
 Functions
 Strength, elasticity and support.

b. Adipose Tissue
 Contains adipocytes, with centrally located triglycerides (fats), nucleus.
 Location: deep to skin, around heart and kidney, behind eyeball.
 Function
 Reduces heat loss through skin, serves as an energy reserve, support and
protects.

c. Reticular Connective Tissue
 It is a network of interlacing reticular fibers and reticular cells.
 Location: Forms the stroma of liver, spleen, and lymph nodes and around the
blood vessels and muscles.
 Function
 Binds together smooth muscle tissue cells, filter and removes worn out blood
cells in the spleen and microbes in lymph nodes.

II. Dense Connective Tissue
a. Dense regular connective tissue
 Bundles of collagen fibers are regularly arranged in parallel patterns for
strength.
 Location: Tendons and most ligaments.
 Function
 Provide strong attachment between various structure.

b. Dense Irregular Connective Tissue
 Collagen fibers are usually irregularly arranged.
 Location: Reticular region of dermis of skin, joint capsule, pericardium of the
heart and heart valves.
 Function
 Provides strength.

c. Elastic Connective Tissue
 Contain branching elastic fibers, fibroblast are present in spaces between
fibres.
 Location: Lung tissue, walls of arteries, trachea, bronchial tube and ligaments
between fibres.
 Function
 Allow stretching of various organs.

III. Cartilage
a. Hyaline cartilage
 Most abundant cartilage in the body.
 Location: ends of long bones, anterior ends of ribs, nose, parts of larn
 Function
 Provide flexibility and support.
 Provide smooth surfaces for movement at joints.

b. Fibrocartilage
 It consist of chondrocytes are scattered among bundles of collagen fibers
within the extracellular matrix.
 Location: Found in intervertebral disc (between vertebrae), tendons.
 Function
 Support and fusion.

c. Elastic Cartilage
 Chrondrocytes are located within a threadlike network of elastic fibers.
 Location: part of external ear and auditory tubes.
 Function
 Gives support and maintain shapes.

IV. Bone tissue
 Compact bone: it consist of osteons that contain lamellae, lacunae,
osteocytes canaliculi and central canals.
 Spongy bone tissue consist of thin columns called trabeculae, spaces
between trabeculae are filled with red bone marrow.
 Location: both compact and spongy bone tissuemake up the various parts
of bone of the body.
 Function
 Support, protection, storage and houses blood forming tissues.

V. Liquid Connective Tissue
a. Blood tissue
 It consist of blood plasma and formed elements, RBC (red blood cells),
white blood cells (leukocytes) and platelets.
 Location: Within blood vessels (arteries, venules, veins) and within the
chamber of the heart.
 Function
 RBC transport oxygen and some CO2.
 WBC carry on phagocytosis and involved in immune system responses.
 Platelets are essential for clotting of the blood.

b. Lymph
 It consist of plasma like liquid components and lymphocytes as formed
elements.
 Location: Within lymphatic vessels.
 Function
 Involved in the defence of the body against infection.
 Transport fats in the form of chylomicrons from intestine to blood
circulation.

3. Muscular Tissue
 Consists of elongated cells called muscle fibers or myocytes for contraction.
 Cells use ATP to generate force.
 Muscular tissue classified into 3 types:
I. Skeletal muscle tissue
II. Cardiac muscle tissue
III. Smooth muscle tissue

I. Skeletal Muscle Tissue
 It consist of long, cylindrical, striated fibres with many peripherally nuclei,
voluntary control.
 Location: Attached to bone by tendons.
 Function
 Motion, posture, heat production and protection.

II. Cardiac muscle tissue
 It consist of branched, striated, fibres with one or two centrally located
nuclei, contains intercalated discs, involuntary control.
 Location: Heart wall
 Function
 Pumps blood to all parts of the body.

III. Smooth Muscle Tissue
 It consist of spindle shaped, nonstriated fibres with one centrally located
nucleus, involuntary control.
 Location: Iris of eyes, walls of hollow internal structures such as blood
vessels, airways of lungs, stomach, intestine, gall bladder, urinary bladder
and uterus.
 Function
 Motion (constriction of blood vessels and airways, propulsion of food
through GI tract, contraction of urinary bladder and gall bladder).

4. Nervous Tissue
 Consists of two principle types of cells
a. Neurons or nerve cells
b. Neuroglia
a. Neurons: It consist of a cell body and processes extending from the cell
body (multiple dendrites and a single axon).
b. Neuroglia: They do not generate or conduct nerve impulses but have other
important supporting functions.

 Location: Nervous system
 Function
 Exhibit sensitivity to various types of stimuli, converts them into nerve
impulses (action potentials) and conducts nerve impulses to other neurons,
muscle fibre or glands.

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