epithelium - doctor 2017 - ju medicine€¦ · surface (2) goblet cells. 3/12/2018 ... it consists...

EPITHELIUM

3/12/2018امجد الشطرات و .ماهر الحديدي د. درويش بدران د. د

احسان العمري

احسان العمري2

1- SIMPLE SQUAMOUS EPITHELIUM

It is a single layer of flat cells

that resembles a tiled floor

when viewed from apical

surface; centrally located

nucleus that is flattened and

oval or spherical in shape.

A) Forms the epithelial

layer of

serous membranes

a- PERITONEUM

b-PLEURA

c-PERICARDIUM

where it is called

Mesothelium

Most common locations of the simple squamous epithelium

Simple squamous epithelium, mesovarium, human, H&E

centrally located

nucleus that is

flattened and oval

or spherical in

Facilitates the movement of

the viscera

(B) lines the cardiovascular and lymphatic system

(heart, blood vessels, lymphatic vessel linings),

where it is known as

ENDOTHELIUM

Provides a physical barrier

between

the circulating blood and the

subendothelial tissues

Produces vasoactive agents that

Constriction and relaxation

of underlying vascular smooth

muscles, thus affecting

the blood pressure!!!!!

(C)-Alveoli (air sacs of lungs) of lungs

diffusion of oxygen into

blood vessels of lungs)

glomerular

(Bowman’s)

capsule of

kidneys

Present at sites of filtration

(such as blood filtration in kidneys)

Single layer of

cube-shaped

cells;

round, centrally

located nucleus.

Cuboidal cell

shape is obvious

when tissue is

sectioned and

viewed from the

Its main

functions are

Secretion and

absorption.

❖lines kidney tubules

❖Makes up secreting portion of some glands such as

thyroid gland

❖Ducts of some glands such as pancreas

❖The smallest conducting bronchioles of the lung

Locations of the simple cuboidal epithelium

Surface of Ovary

lines anterior surface of capsule of lens of the

forms pigmented epithelium at posterior

surface of retina of the eye

Read only

lines kidney tubules

cuboidal cells (CC).

This photomicrograph

shows two pancreatic

ducts (PD) that

are lined by a simple

cuboidal epithelium

CILIATED SIMPLE COLUMNAR EPITHELIUM Single layer of ciliated

column like cells with

oval nuclei near base of

cells. Goblet cells are

usually interspersed

among ciliated columnar

epithelia

❖Lines some bronchioles (small tubes) of respiratory tract

❖Uterine (fallopian) tubes

CILIATED SIMPLE COLUMNAR EPITHELIUM

Locations of the

Some paranasal sinuses

Central canal of spinal cord

Ventricles of brain

Read only

Cilia help move oocytes

expelled from ovaries

through uterine

(fallopian) tubes into

uterus

SIMPLE COLUMNAR NONCILIATED

Single layer of nonciliated

column like cells with

oval nuclei near base of cells;

contains

(1) columnar epithelial cells

with microvilli at apical

surface

(2) goblet cells

Location Lines gastrointestinal tract (from stomach to anus), ducts of many

glands, and gallbladder

Function Secretion

and absorption; larger

columnar cells contain

more organelles and

thus are capable of

higher level of

secretion and

absorption than

are cuboidal cells

E.Pseudostratified columnar

Pseudostratified epithelium:(pseudo= false)

• Tissue appears to be several layers but is really a single layer.

• Cells nuclei lie at different levels and cells appear to have multiple layers.

• All its cells rest on the base but not all of them reach the surface.

3/12/2018 امجد الشطرات و احسان العمري.ماهر الحديدي د. درويش بدران د. د 24

1. Ciliated: Form of cells with cilia and Goblet cells.

• Locations: Lines airways of most of upper respiratory tract.

• Functions: Secretes mucus that traps foreign particles.

2.Nonciliated: Contains cells without cilia and lack goblet cells.Locations: Lines larger ducts of many glands & epididymis.

Functions: Absorption and protection.

➢ Two or more layers of cells

➢ cells in apical layer and several layers deep to it are squamous cells in deeper

layers vary from cuboidal to columnar.

➢ As basal cells divide, daughter cells arising from cell divisions push upward

toward apical layer.

➢ As daughter cells move toward surface and away from blood supply in

underlying connective tissue, they become dehydrated and less metabolically

active.

➢ Tough proteins predominate as cytoplasm is reduced, and cells become tough,

hard structures that eventually die.

➢ At apical layer, after dead cells lose cell junctions they are

sloughed off, but they are replaced continuously as new cells emerge from basal

cells.

Stratified epithelium

II. Stratified epithelium

Types:

a. Stratified squamous• keratinized

• Nonkeratinized.

b. Stratified cuboidal epithelium.

c. Stratified columnar epithelium.

d. Transitional epithelium.

A-Stratified squamous epithelium

Two types:•Keratinized (dry).

•Nonkeratinized (wet).

Keratinized stratified squamous epithelium develops tough layer of keratin in

apical layer of cells and several layers deep to it

(Keratin is a tough, fibrous intracellular protein that helps protect skin and

underlying tissues from heat, microbes, and chemicals.) Relative

amount of keratin increases in cells as they move away from nutritive blood

supply and organelles die

Keratinized stratified squamous :

• Covers dry surfaces such as epidermis of skin (superficial layer of the skin). Formtough layer of keratin (tough protein) between surface cells.

• Functions:

Protect skin and underlying tissues from heat, microbes, chemicals and water loss.

Nonkeratinized stratified squamous

• Surface layers contain small amount of keratin and always wet.

• Location: Lines wet surfaces as lining of mouth, esophagus, part of epiglottis, part of pharynx, and vagina) and covers tongue

• Function: Protection against scratch, water loss, ultraviolet radiation, and foreign invasion.

• Both types form first line of defense against microbes.

STRATIFIED CUBOIDAL EPITHELIUM

Location Ducts of adult sweat glands and

esophageal glands, part of male urethra.

Basal layers usually consist of shortened,

irregularly shaped cells; only apical layer has

columnar cells; uncommon.

STRATIFIED COLUMNAR EPITHELIUM

Location Lines part of urethra;

large excretory ducts of some

glands, such as esophageal

glands; small areas in anal

mucous membrane;

part of

conjunctiva of eye.

TRANSITIONAL EPITHELIUM

• Locations: Urinary bladder, ureter.

• Functions: Allow the organ to stretch and protection from rupturing.

➢ Variable appearance (transitional)

➢ In relaxed or unstretched state, looks like stratified cuboidal epithelium, except apical layer

cells tend to be large and rounded.

➢ As tissue is stretched, cells become flatter, giving the appearance of stratified squamous

epithelium.

➢ Multiple layers and

elasticity make it ideal for lining hollow structures (urinary bladder) subject to expansion from

within

Location Lines urinary bladder and portions of

ureters and urethra

Function Allows

urinary organs to

stretch and maintain

protective lining while

holding variable

amounts of fluid

without rupturing

is a disorder of the small intestine in which one of the

first pathologic changes

is loss of the microvilli brush borderof the absorptive cells

This is caused by

an immune reaction

against the wheat protein gluten during its digestion, which

produces diffuse enteritis (intestinal inflammation), changes

to the epithelial cells leading to malabsorption, and eventually

to pathologic changes in the intestinal wall.

The malabsorption

problems and structural changes

are reversible

when gluten is removed from the diet.

Celiac disease

also called gluten-sensitive enteropathy

Several mutations have been described in the proteins of

the cilia and flagella. They are responsible for the immotile

cilia syndrome (Kartagener syndrome), whose symptoms

are chronic respiratory infections caused by the lack of the

cleansing action of cilia in the respiratory tract and

immotile

spermatozoa, causing male infertility

➢ Sometimes termed basket cells

➢ Fusiform or stellate in shape

➢ Contain actin and myosin filaments and contract

when stimulated by nervous or endocrine signals.

➢They surround the secretory portions and ducts of

some glands, e.g.mammary, lacrimal, salivary and

sweat glands

➢Their contraction assists the initial flow of

secretion into larger conduits.

Myoepithelial cells

surface epithelium and its underlying connective tissue are regarded as a functional unit

called a membrane.

40امجد الشطرات و .ماهر الحديدي د. درويش بدران د. د

Mucus membrane, also called mucosa, lines those cavities that connect

with the outside of the body, namely, the alimentary canal, the respiratory

tract, and the geni-tourinary tract. It consists of surface epithelium (with or

without glands), a supporting connective tissue called the lamina propria,

Serous membrane, also called serosa, lines the peritoneal, pericardial, and pleural

cavities. These cavities are usually described as closed cavities of the body, although in

the female the peritoneal cavity communicates with the exterior via the genital tract.

Structurally, the serosa consists of a lining epithelium, the mesothelium, a supporting

connective tissue, and a basement membrane between the two. Serous membranes do not

contain glands, but the fluid on their surface is watery.

The two types of membrane are mucus

membrane and serous membrane.

3/12/2018

epithelium - doctor 2017 - ju medicine€¦ · surface (2) goblet cells. 3/12/2018 ... it consists...

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