2. Epithelium is the collection of cells with very
little intercellular substance lining internal and
external surfaces of body and performing
similar function
3. EPI = UPON
THELE = NIPPLE
DERIVED FROM ALL THREE EMBRYONIC
GERM LAYERS
Basal layer of epithelium rest on BASEMENT
MEMBRANE
4. Basement membrane consists of
Basal lamina
proteoglycans, type 1V collagen, electron microscopic
- Forms limit of cell
- Secreted by epithelial cells
Reticular lamina
- Consist of fine collagen fibers
9. SINGLE LAYER OF CUBOIDAL CELLS
For secretion
Sites=thyroid follicles, tubules of
kidney, surface of ovary
All cells of same height and width and rest on
basement membrane
10.
11. Tall cells on basement membrane
Nucleus near base
For absorption and secretion
ciliated = uterus
Non ciliated = GIT, (has brush border –
microvilli, folds of cell membrane to increase
surface area
12.
13. S. sq. keratinized
Surface layer is squamous
In between 3-7 layers are polygonal to flat
Basal layer is cuboidal
There is layer of keratin at the the top
Sites. skin
S. Sq. Non-keratinized
No keratin layer
Same as other
sites= esophagus, anal canal, vagina
14.
15.
16. Stratified Cuboidal epithelium
Two to three layers of cells
Mostly present in ducts of salivary glands.
Stratified Columnar epithelium
Two to three layers of cells
Present in ducts of salivary glands, Urethra.
17. ALL LAYERS REACH BASEMENT
MEMBRANE
Nuclei at different levels
Trachea
Has goblet cells
18. Empty urinary bladder
Basal layer columnar
Intermediate layers polygonal 2-3 layers
Flask shaped layers
Dome shaped( umbrella) at top
Stretched urinary bladder
2-3 layers of flat cells
19. Needed for cell aggregation and cohesion
Marked in epithelial tissue
Due to binding action of glycoproteins
Lateral membranes have special junctions
For adhesion
Act as seals for flow of materials
Present in definite order from apex to base
20.
21.
22. Tight junctions – ZONULA OCCLUDENS
Most apical
Belt like , totally occluding (Closing)
Have ridges and grooves forming net like structure
Form tight seal (e.g Urinary bladder) to control paracellular
pathway
ZONULA ADHERENS
Belt like
Encircles cell
For adhesion of neighbouring cells
Forms terminal web on cytoplasmic surface of cell membrane
23. Gap junctions –NEXUS
Present anywhere
Present in all tissues except skeletal muscle
There is gap of 2 nm in between opposing surfaces
Protiens of junction make connexons which control
the flow
Permits molecules less than 1500 Da.
Eg. Heart muscle.
24. DESMOSOMES:MACULA ADHERENS
Disc like structure
Membrane > 30 nm apart
Dense material in intracellular space DESMOSIN for
adhesion
Attechment plaque protiens inside the cell
membrane
HEMIDESMOSOMES (Half Desmosomes)
Are between basal surface of epithelial cells and
basement membrane.
27. For specific activities at the cell mambrane
Microvilli
Fingerlike folds of cell membrane
Increase surface area
Present in absorptive cells e. g. small intestine where
the make brush or striated border
1 um in height and 0.08 um wide
Within mv are clusters of actin microfilaments
forming terminal web at the base
28.
29. STEREOCILIA
Long nonmotile processes of cell
Long microvill
Present in epididymis
Increase surface area for molecular movement
CILIA AND FLAGELLA
Long, motile hair like structures
5-10 um long and 0.2 in dia
Surrounded by the cell membrane
Contain central pair of microtubule surrounded by9
pairs of microtubules
Inserted into basal body, inside the cell
Cilia eg. In trachea for movement of mucous
Flagela eg in sperms. Tail like movement