Epithelial tissue

Mrs. Dalia Kamal Eldien

MSC in Microbiology Lecture NO 2

To explain What is epithelium.

What are the types of epithelium and their functions.

What are the locations of different epithelium in human

body.

Objectives

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

DEFINITION:

Epithelium is a type of animal tissue made up of layers of

closely packed cells, with very little intercellular space.

Definition of Epithelium

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.

Characteristic of epithelial

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)

Functions

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 membrane

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.

Basement membrane

Functions of the Basement Membranes:

1) Provides support and attachment for the epithelial cells

2) Selective diffusion barrier

Basement membrane

Epithelium can be classified by:

1.Number of cell layers

2.Shape of uppermost cells

Classification of epithelial

Classification of epithelia

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

Classification of epithelia

Epithelial 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.

Epithelial cells

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 epithelial tissue

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 epithelial

Simple squamous epithelium

Simple squamous epithelium

SIMPLE SQUAMOUS EPITHELIUM

• LOCATION

• Endothelium: heart, blood vessels, lymphatic.

• Mesothelium : Pericardium, pleura ,peritoneum.

• others： alveoli of the lungs, in kidney tubules etc

2.Simple cubiodal epithelium  

These cells may have secretory, absorptive, or excretory

functions. examples include small collecting ducts of

kidney, pancreas and salivary gland.

Simple cubiodal epithelial

Simple cubiodal epithelial

SIMPLE CUBIODAL EPITHELIUM

LOCATION

1. In most of glands like salivary, mammary etc

2. In collecting ducts of kidneys

Simple cubiodal epithelial

3.Simple columnar epithelium.

found in areas with extremely high secretive (as in

wall of the stomach), or high 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 epithelial tissue

Simple columnar epithelial

Simple columnar epithelial

SIMPLE COLUMNAR EPITHELIUM LOCATION

Mostly located in the lining of small intestine

Types of epithelial

STARTIFIED EPITHELIUM

1. Stratified squamous epithelium

2. Stratified cuboidal epithelium

3. Stratified columnar epithelium

OTHER TYPES

4. Pseudo stratified columnar epithelium

5. Transitional epithelium

Types of epithelial

STRATIFIED SQUAMOUS EPITHELIUM

LOCATION

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

Types of epithelial

STRATIFIED SQUAMOUS EPITHELIUM

STRATIFIED SQUAMOUS EPITHELIUM

STRATIFIED CUBIODAL EPITHELIUM

LOCATION

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

Types of epithelial cells

STRATIFIED CUBIODAL EPITHELIUM

STRATIFIED CUBIODAL EPITHELIUM

Stratified columnar epithelium

LOCATION

Located in male urethra

Types of epithelial

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 epithelial cells

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.

LOCATION

Located in the inner lining of urinary bladder

Types of epithelial cells

TRANSITIONAL EPITHELIUM

Types of epithelial cells

Classification of epithelial tissue

Home work

Describe the following• Squamous, Cuboidal and columnar

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

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

so ?????????