Objectives

To explain What is epithelium.

What are the types of epithelium and their functions.

What are the locations of different epithelium in

human body.

oDespite its complexity, the human body is composed of only four basic types of tissue:- Epithelial tissue Connective tissueMuscular tissue Nervous tissueoThese tissues, which all contain cells and molecules of the extracellular matrix (ECM), exist in association with one another and in variable proportions and morphologies, forming the different organs of the body.

introduction

EPITHELIUMDEFINITION:

Epithelium is a type of animal tissue made up of layers

of closely packed cells, with very little intercellular

space.

Characteristic features of epithelial cells

1) Covers the internal and external surfaces of body.

2) Forms the linings of body cavities and vessels.

3) Have no blood supply (AVASCULAR)

4) Can easily regenerate if well nourished.

FUNCTIONS OF EPITHELIUM

1) Covering, lining, and protecting surfaces (eg, skin)

2) Absorption (eg, the intestines)

3) Filtration (eg, the blood capillaries of kidney)

4) Secretion (eg, the epithelial cells of glands)

Basement Membranes

Epithelial tissue rests on a basement membrane, a thin delicate membrane of protein fibers and glycosaminoglycans separating an epithelium from underlying tissue, which acts as a scaffolding on which epithelium can grow and regenerate after injuries

The basement membrane is composed of:

1) Basal lamina

2) Reticular lamina.

Basement Membranes

1) Basal lamina:The basal lamina is secreted by the epithelial cells.

Visible only with the electronic microscope

1) Reticular lamina.Is secreted by fibroblasts located in the underlying connective tissue.

Functions of the Basement Membranes:

1) Provides support and attachment for the epithelial cells

2) Selective diffusion barrier

Basement Membranes

Epithelium can be classified by:

1.Number of cell layers

2.Shape of uppermost cells

Classification of epithelia tissue

Classification of epithelia tissue

Simple epithelium:

1) One cell layer thick

2) All cells rest on the basement membrane

Stratified epithelium

3) More than one cell layer thick

4) Only the deepest layer of cells contact the basement

membrane

Classification of epithelia tissue

Classification of epithelia tissue

EPITHELIUM cells

o There are three principal morphologies associated with epithelial cells:

Squamous epithelium has cells that are wider than they are tall (flat and scale-like) ), Nucleus flat, central.

Cuboidal epithelium has cells whose height and width are approximately the same (cube shaped), Nucleus spherical .

Columnar epithelium has cells taller than they are wide (column-shaped), Nucleus oblong basal.

EPITHELIUM cell

First name of tissue indicates number of cell layers: Simple – one layer of cells Stratified – more than one layer of cells Last name of tissue describes shape of cells Squamous Cuboidal columnar

Naming the epithelium

SIMPLE EPITHELIUM:

1. Simple squamous epithelium

is one cell thick; that is, every cell is in direct contact

with the underlying basement membrane. In general,

it is found where absorption and filtration occur. The

thinness of the epithelial barrier facilitates these

processes

TYPES OF EPITHELIA

Simple squamous epithelium

Simple squamous epithelium

SIMPLE SQUAMOUS EPITHELIUM

• Endothelium : heart, blood vessels, lymphatic.

• Mesothelium : Pericardium,

pleura ,peritoneum. • others： alveoli of the lungs, in kidney

tubules etc

TYPES OF EPITHELIA

2.Simple cubiodal epithelium

these cells may have secretory, absorptive, or

excretory functions. examples include small

collecting ducts of kidney, pancreas and salivary

gland.

TYPES OF EPITHELIA

Simple cubiodal epithelium

Simple cubiodal epithelium

SIMPLE CUBIODAL EPITHELIUM

LOCATION 1. In most of glands like salivary, mammary etc

2. In collecting ducts of kidneys

Simple cuboidal epithelium

3.Simple columnar epithelium.

found in areas with extremely high secretive (as in wall of

the stomach), or absorptive (as in small intestine) areas.

they possess cellular extensions (e.g. microvilli in the small

intestine, or cilia found almost exclusively in the female

reproductive tract).

TYPES OF EPITHELIA

TYPES OF EPITHELIA Simple columnar epithelium

Simple columnar epithelium

SIMPLE COLUMNAR EPITHELIUM

LOCATION

Mostly located in the lining of small intestine

TYPES OF EPITHELIA

STARTIFIED EPITHELIUM

1. Stratified squamous epithelium

2. Stratified cuboidal epithelium

3. Stratified columnar epitheliumOTHER TYPES

4. Pseudo stratified columnar epithelium

5. Transitional epithelium

TYPES OF EPITHELIA

STRATIFIED SQUAMOUS EPITHELIUM

LOCATION

• outer layers of skin, linings of oral cavity, throat, vagina, and anal canal

TYPES OF EPITHELIA

STRATIFIED SQUAMOUS EPITHELIUM

STRATIFIED SQUAMOUS EPITHELIUM

STRATIFIED CUBIODAL EPITHELIUM

LOCATION

Mostly located in the ducts of salivary , sweat and mammary glands

TYPES OF EPITHELIA

STRATIFIED CUBIODAL EPITHELIUM

STRATIFIED CUBIODAL EPITHELIUM

Stratified columnar epithelium

LOCATION

Located in male urethra

TYPES OF EPITHELIA

Stratified columnar epithelium

Stratified columnar epithelium

PSEUDOSTRATIFIED COLUMNAR EPITHELIUMPseudo means (false)1. Appears stratified because nuclei are at 2 or more

levels2. NOT stratified because all cells touch basement

membrane. It can be ciliated or non ciliated. LOCATIONoNon ciliated variety is located in the ducts of male reproductive systemoCiliated type is located in upper respiratory tract eg trachea.

TYPES OF EPITHELIA

PSEUDOSTRATIFIED COLUMNAR EPITHELIUM

PSEUDOSTRATIFIED COLUMNAR EPITHELIUM

CILIATED PSEUDOSTRATIFIED COLUMNAR EPITHELIUM

TRANSITIONAL EPITHELIUM

The transitional epithelium is named so because it can transit between two states.

1. In empty bladder cells are umbrella shaped and

show many layers.

2. In full bladder cells become flattened and show less layers.

LOCATIONLocated in the inner lining of urinary bladder

TYPES OF EPITHELIA

TRANSITIONAL EPITHELIUM

TYPES OF EPITHELIA

Classification of epithelia tissue

Home workDescribe the following• Squamous, Cuboidal and columnar epithelium

cells ???????• Write shortly on the classification of

epithelial cells ???????Why the transitional epithelium named

so ?????????