The document provides a comprehensive overview of human tissues and their classifications, discussing the four major types of adult tissues: epithelial, connective, muscle, and nervous tissues. It elaborates on the functions, structures, and properties of these tissues, including histological terms, major cell types, and the extracellular matrix. Additionally, it covers the embryonic origins of tissues and the effects of aging on tissue functionality and repair.

1. MR.AMADI.K.O

2. • Tissues - collections of similar cells and the substances
surrounding them
• Tissue classification based on structure of cells, composition
of noncellular extracellular matrix, and cell function
 Major types of adult tissues
 Epithelial
 Connective
 Muscle
 Nervous
 Histology: Microscopic Study of Tissues
 Biopsy: removal of tissues for diagnostic purposes
 Autopsy: examination of organs of a dead body to
determine cause of death

3.  3 major germ layers that form the embryonic disc (source of stem cells)
 Endoderm
 Inner layer
 Forms lining of digestive tract and derivatives
 Mesoderm
 Middle layer
 Forms tissues as such muscle, bone, blood vessels
 Ectoderm
 Outer layer
 Forms skin and neuroectoderm

4.  Cellularity - Consists almost
entirely of cells
 Covers body surfaces, lines
hollow organs, and forms
glands
 Outside surface of the body
 Lining of digestive, respiratory
and urogenital systems
 Heart and blood vessels
 Linings of many body cavities
 Polarity - Has apical, basal, and
lateral surfaces
 Rests on a basement membrane
 Specialized cell contacts bind
adjacent cells together
 Avascular - no blood vessels
 Regenerative -Replaces lost
cells by cell division

5.  Protecting underlying structures; e.g.,
epithelium lining the mouth
 Acting as barriers; e.g., skin
 Permitting the passage of substances; e.g.,
cells lining air sacs in lungs and nephrons in
kidney
 Secreting substances; e.g., pancreatic cells
 Absorbing substances; e.g., lining of
stomach and small intestine

6. Figure 4.1

7.  Number of layers of cells
 Simple- one layer of cells. Each extends from
basement membrane to the free surface
 Stratified- more than one layer.
 Pseudostratified- tissue appears to be stratified,
but all cells contact basement membrane so it is
in fact simple
 Shape of cells
 Squamous- flat, scale-like
 Cuboidal- about equal in height and width
 Columnar- taller than wide

9. Figure 4.3a

10. Figure 4.3b

11. Figure 4.3c

12. Figure 4.3d

13.  Contain two or more layers of cells
 Regenerate from below
 Major role is protection
 Are named according to the shape of cells at
apical layer

14.  Description
 Many layers of cells – squamous in shape
 Deeper layers of cells appear cuboidal or columnar
 Thickest epithelial tissue – adapted for protection

15.  Specific types
 Keratinized – contain the protective protein keratin
 Surface cells are dead and full of keratin
 Non-keratinized – forms moist lining of body
openings

16.  Function – Protects underlying tissues in areas
subject to abrasion
 Location
 Keratinized – forms epidermis
 Non-keratinized – forms lining of esophagus, mouth,
and vagina

17. Figure 4.3e

18.  It is a rare type of epithelial tissues composed
of column shaped cells arranged in multiple
layers

20. STRATIFIED CUBOIDAL EPITHELIUM
 Thin, stratified epithelium which usually consists of only
two or three layers of cuboidal or low columnar cells.
 Not involved in significant absorptive or secretory activity
PRESENT IN:
Ducts of sweat glands
Large ducts of exocrine glands
Anorectal junction

22.  FUNCTION:
 Absorption
 Secretion

23.  Photomicrograph

24. Figure 4.3h

25.  A gland is one or more cells that makes and secretes
an aqueous fluid
 Two types of glands formed by infolding of
epithelium:
 Endocrine: no contact with exterior of body; ductless; produce
hormones (pituitary, thyroid, adrenals, pancreas)
 Exocrine: open to exterior of body via ducts (sweat, oil)
 Exocrine glands classified either by structure or by
the method of secretion
 Classified by structure
 Unicellular: goblet cells
 Multicellular: sweat, oil, pituitary, adrenal

26.  Classified on the basis of types
of ducts or mode of secretion
 Types of ducts
 Simple: ducts with few
branches
 Compound: ducts with
many branches
 If ducts end in tubules or
sac-like structures: acini.
Pancreas
 If ducts end in simple sacs:
alveoli. Lungs

27.  Tight junctions
 Desmosomes
 Gap junctions

28. • Integral proteins of adjacent
cells fuse together
• Completely encircle the cell
and form an adhesion belt.
• Form an impermeable
junction.
• Common near apical region

29.  Desmosomes – two disc-like plaques connected
across intercellular space
 Plaques of adjoining cells are joined by proteins
called cadherins
 Proteins interdigitate into extracellular space
 Intermediate filaments insert into plaques from
cytoplasmic side

30. Figure 3.5b
Linker proteins extend
from plaque like teeth of
a zipper.
Intermediate filaments
extend across width of
cell.
• Common in superficial layers of skin; skin
peels after a sunburn
• Reduces chance of tearing, twisting, stretching

31. • Connexon proteins are trans-
membrane proteins.
• Present in electrically excitable
tissues (heart, smooth muscle)

32.  Noncellular supporting sheet between the
epithelium and the connective tissue deep to it
 Consists of proteins secreted by the epithelial
cells
 Functions:
 Acts as a selective filter, determining which
molecules from capillaries enter the epithelium
 Acts as scaffolding along which regenerating
epithelial cells can migrate
 Basal lamina and reticular layers of the
underlying connective tissue deep to it form
the basement membrane

33.  Apical surface features
 Microvilli – finger-like extensions of plasma
membrane
 Abundant in epithelia of small intestine and kidney
 Maximize surface area across which small molecules
enter or leave
 Cilia – whip-like, highly motile extensions of apical
surface membranes
 Movement of cilia – in coordinated waves

34.  Most diverse and abundant tissue
 Main classes
 Connective tissue proper
 Cartilage
 Bone tissue
 Blood
 Characteristics
 Mesenchyme as their common tissue of origin
(mesenchyme derived from mesoderm)
 Varying degrees of vascularity
 Nonliving extracellular matrix, consisting of ground
substance and fibers
 Cells are not as abundant nor as tightly packed
together as in epithelium

35. Figure 4.5

36.  Enclose organs as a capsule and separate
organs into layers. Areolar
 Connect tissues to one another. Tendons
and ligaments.
 Support and movement. Bones.
 Storage. Fat.
 Insulation. Fat.
 Transport. Blood.
 Protection. Bone, cells of the immune
system.

37.  Ground substance – unstructured material
that fills the space between cells
 Fibers – collagen, elastic, or reticular
 Cells – fibroblasts, chondroblasts, osteoblasts,
hematopoietic stem cells, and others

38.  Fibroblasts - secrete the proteins needed for fiber
synthesis and components of the extracellular matrix
 Adipose or fat cells (adipocytes). Common in some
tissues (dermis of skin); rare in some (cartilage)
 Mast cells. Common beneath membranes; along small
blood vessels. Can release heparin, histamine, and
proteolytic enzymes in response to injury.
 Leukocytes (WBC’s). Respond to injury or infection
 Macrophages. Derived from monocytes (a WBC).
Phagocytic; provide protection
 Chondroblasts - form cartilage
 Osteoblasts - form bone
 Hematopoietic stem cells - form blood cells
 Undifferentiated mesenchyme (stem cells). Have
potential to differentiate into adult cell types.

39.  ECM has 3 major components
1. Protein fibers 2. Ground substance 3. Fluid
 Protein fibers
 Collagen fibers. Composed of the protein collagen.
Strong, flexible, inelastic; great tensile strength (i.e.
resist stretch). Perfect for tendons, ligaments
 Elastic fibers. Contain molecules of protein elastin
that resemble coiled springs. Returns to its original
shape after stretching or compression. Perfect for
lungs, large blood vessels
 Reticular fibers. Formed from fine collagenous fibers;
form branching networks (stroma). Fill spaces
between tissues and organs.

40.  Interstitial (tissue) fluid within which are one or more
of the molecules listed below: ( Can be fluid,
semifluid, gelatinous or calcified.)
 Hyaluronic acid: a polysaccharide. Very slippery;
serves as a good lubricant for joints. Common in
most connective tissues.
 Proteoglycans: protein and polysaccharide
complex. Polysaccharides called glyocosaminoglycans
(chondroitin sulfate, dermatan sulphate, keratan
sulfate). Protein part attaches to hyaluronic acid.
Able to trap large amounts of water.
 Adhesive molecules: hold proteoglycan aggregates
together. Chondronectin in cartilage, osteonectin in
bone, fibronectin in fibrous connective tissue.
 Functions as a molecular sieve through which
nutrients diffuse between blood capillaries and cells

41.  Mesenchyme: source of
all adult connective
tissue.
 Derived from mesoderm
 Delicate collagen fibers
embedded in semifluid
matrix
 Mucus: found only in the
umbilical cord. Wharton’s
jelly.

42. Figure 4.12b

43. Figure 4.12c

44. Figure 4.12d

45. Figure 4.12e

46. Figure 4.12f

47.  Bundles and sheets of collagenous and elastic fibers
oriented in multiple directions
 In walls of elastic arteries (aorta), lungs, vocal
ligaments
 Strong, yet elastic; allows for recoil of tissue after
being stretched

48.  Consists of a large network of collagen & elastic fibres
firmly embedded in chondroitin sulfate.
 Composed of chondrocytes (cells) which occur in
surrounded spaces called lacunae.
 Type of cartilage determined by components of the
matrix.
 Firm consistency.
 Ground substance: Proteoglycans and hyaluronic acid
complexed together trap large amounts of water
(microscopic sponges). Allows tissue to spring back after
being compressed.
 Avascular and no nerve supply. Heals slowly.
 Perichondrium. Covering of Dense irregular connective
tissue that surrounds cartilage. Fibroblasts of
perichondrium can differentiate into chondroblasts
(cartilage-forming cells)
 Types of cartilage
 Hyaline
 Fibrocartilage

49. Figure 4.12g

50. Figure 4.12h

51. Figure 4.12i

52.  Bone tissue
 Cartilage, joints and bones make up the skeletal
system.
 Bones store calcium & phosphorous, house the
red bone marrow& yellow marrow.
 Bones are organs composed of several
connective tissue eg bone(osseus) tissue,
periosteum, red & yellow marrow and
endosteum.
 Bone is classified as either compact or spongy
depending on the arrangement ECM.
 Compact bone basic unit is an osteon or
haversian system and have four parts.

53.  Lamellae – concentric rings of ECM that consist
of mineral salts which give bones its hardness
& collagen fibre for strength.
 Responsible for compact nature.
 Lacunae – small spaces between lamellae that
contain mature bone cells. Osteocytes.
 Canaliculi – projections from the lacunae.
Canals containing processes of osteocytes.
Provide nutrients and routes of excretion.
 A central (haversian) canal – contain blood
vessels and nerves.
 Spongy bone lacks osteon- consists of columns
of bones called trabeculae. Which contain
lamellae, osteocytes laculae & canaliculi.

54. Figure 4.12j

55. Figure 4.12k

56.  Characteristics
 Cells are referred to as muscle fibers or myocytes
 Contracts or shortens with force when stimulated
 Moves entire body and pumps blood
 Types
 Skeletal: attached to bones
 Cardiac: muscle of the heart.
 Smooth: muscle associated with tubular structures
and with the skin. Nonstriated and involuntary.

57. Figure 4.14a

58. Figure 4.14b

59. Figure 4.14c

60. Special characteristics of neurons
 Longevity – can live and function for a lifetime
 Do not divide (amitotic) – fetal neurons lose their
ability to undergo mitosis; neural stem cells are an
exception
 High metabolic rate – require abundant oxygen
and glucose

61. Parts of the Neuron
Cell Body. Aka Soma or Perikaryon
Contains usual organelles plus
other structures
Nissl bodies = chromatophilic
substance = rough E.R: primary
site of protein synthesis
Cytoskeleton of neurofilaments
and neurotubules
No centrioles (hence its amitotic
nature)
Major biosynthetic center
Most neuronal cell bodies
Located within CNS
Ganglia - clusters of cell bodies
that lie along nerves in PNS
Tapers to form axon hillock

62. Figure 4.15

66.  Nerves - bundles of axons wrapped in
connective tissue
 If only sensory axons, called sensory nerves
 If only motor axons, called motor nerves
 If both sensory and motor axons, called mixed nerves
 Connective Tissue Coverings
 Endoneurium – layer of delicate connective tissue
surrounding the axon
 Nerve fascicles – groups of axons bound into bundles
 Perineurium – connective tissue wrapping
surrounding a nerve fascicle
 Epineurium – whole nerve is surrounded by tough
fibrous sheath

67.  Note the similarity of
a nerve to a muscle
1. Just as a muscle is a
collection of muscle
fibers, a nerve is a
collection of nerve
fibers (axons).
2. Each is broken up in
smaller units known
as fascicles

68.  Cells divide more slowly
 Collagen fibers become more irregular in structure, though
they may increase in number
 Tendons and ligaments become less flexible and more fragile
 Elastic fibers fragment, bind to calcium ions, and become
less elastic
 Arterial walls and elastic ligaments become less elastic
 Changes in collagen and elastin result in
 Atherosclerosis and reduced blood supply to tissues
 Wrinkling of the skin
 Increased tendency for bones to break
 Rate of blood cell synthesis declines in the elderly
 Injuries don’t heal as readily