1. Book Recommended:
Basic Histology
Lec. By Dr. Habib Qureshi

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

6.  Simple Epithelium
 Simple Squamous
 Simple Cuboidal
 Simple Columnar
 Stratified Epithelium
 Pseudostratified Epithelium
 Transitional Epithelim

7.  Single layer of flat cells.
 Rest on basement membrane
 Nucleus bulging
 Function: gas exchange, diffusion of fluids
 Endothelium = blood vessels
 Mesothelium = peritoneal, pleural and
pericardial cavities
 Sites= bowman’s capsule, alveoli of
lungs, mesothelium, endothelium, loop of
Henle of kidney

8. Simple Squamous
Epithelium

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

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

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

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

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.

26.  Adhereing junctions
 Z. Adherens
 Hemidesmosomes
 desmosomes
 Impermiable junctions
 Zonula occludens
 Communicating Junctions
 Gap junctions

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

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

31.  The End