Introduction To Histology - Epithelium

Question 1

What is epithelia ?

Answer 1

Type of tissue.
Epithelia are a continuous sheet of cells covering the surfaces of the body.
Include both: surface epithelia + solid organs

Question 2

What does epithelial tissue look like

Answer 2

Cells in close contact
Cells are polarised- supported by basement membrane

Question 3

What does the basement membrane provide for epithelial tissue?

Answer 3

Provides site of attachment
Also separates the epithelium from underlying supporting tissues
Epithelial cells therefore polarised

Question 4

Is epithelial tissue vascular or avascular ?

Answer 4

Avascular -> nourished by connective tissue which have blood vessels

Question 5

What are the function of epithelial tissue ?

Answer 5

Covers and protects surfaces outside and inside of the body

Lines internal cavities, blood vessels and organs

Forms glandular structures

Forms barriers

Combines with nervous tissue to make special senses -> neuroepithelium

Question 6

What are the two major types of epithelia ?

Answer 6

Covering epithelia and glandular epithelia

Question 7

What is covering epithelia and what is its function ?

Answer 7

Covers/lines all body surfaces, cavities, tubes

Question 8

What are glands ?

Answer 8

An organised collection of secretory epithelial cells

Question 9

How are glands formed ?

Answer 9

Development of proliferation/invagination of epithelium -> project into underlying connective tissue

Question 10

What are the two types of glands ?

Answer 10

Exocrine gland
Endocrine gland

Question 11

What are exocrine glands ?

Answer 11

Retain continuity with surface- secrete via duct

Question 12

What are endocrine glands ?

Answer 12

Lose contact with surface when their ducts degenerate during development
-> secrete directly into bloodstream

Question 13

How can epithelia be classified ?

Answer 13

Number of layers
Shapes of cells
Surface specialisations

Question 14

Explain simple in terms of layers

Answer 14

Single layer
Good for absorption/secretion fragile

Question 15

Explain stratified in terms of layers ?

Answer 15

2 or more layers of cells, good for protection

Question 16

Explain pseudostratified in terms of layers

Answer 16

One layer with mixture of cell shapes
Looks stratified as nuclei at different levels and not all cells reach surface
All cells in contact with basement membrane

Question 17

What does a squamous cell look like ?

Answer 17

Squamous - flat shaped

Question 18

What does cuboidal shape look like ?

Answer 18

Cube shaped

Question 19

What does columnar shape of cell look like ?

Answer 19

Tall cylindrical shaped

Question 20

What does a transitional shape cell look like ?

Answer 20

Readily changes shape, accommodates stretching

Question 21

What are the classifications of epithelial tissue ?

Answer 21

Simple squamous
Simple cuboidal
simple columnar
Stratified squamous
Pseudostratified
Transitional

Question 22

What is the structure of simple squamous epithelium

Answer 22

Single layer of flat cells
Irregularly shaped/hexagonal
Compared to scales on a fish

Question 23

What is the function of simple squamous epithelium

Answer 23

Diffusion, filtration, some secretion and protection against friction
Due to delicate thin lining which allows easy passage of fluid

Question 24

Where is simple squamous epithelium sound

Answer 24

Lining of blood vessels and the heart
Alveoli
Lining of serous membranes of the body cavities
Lining of some kidney tubules, etc

Question 25

What is the structure o simple cuboidal epithelium ?

Answer 25

Single layer of cube shaped cells Some cells which are kidney tubules have microvilli

Question 26

What is the function of simple cuboidal epithelium

Answer 26

Good for diffusion Lines small ducts that have excretory, secretory and absorptive functions - good for secretion and absorption

Question 27

Where are simple cuboidal epithelium found

Answer 27

Kidney tubules, Glands and their ducts, Lining of terminal bronchioles of the lungs, Surfaces of the ovaries

Question 28

What is the structure of simple columnar epithelium

Answer 28

Single layer of tall, narrow cells; Nuclei are elongated Some cells have cilia (bronchioles of lungs, auditory tubes, uterine tubes, and uterus) or microvilli (intestines)

Question 29

What is the function of simple columnar epithelium

Answer 29

Movement of substances, absorption and Secretion Offer more protection than flatter cells

Question 30

Where can simple columnar epithelium be found

Answer 30

Location: Glands and some ducts, bronchioles of the lungs, auditory tubes, uterus, uterine tubes, stomach, intestines, gallbladder, bile ducts, ventricles of the brain

Question 31

What is the structure of stratified squamous epithelium

Answer 31

Multiple layers of cells that are cube-shaped in the basal layer and progressively flattened toward the surface

Question 32

The basal layer contains which type of cell ?

Answer 32

Continuously dividing stem cells

Question 33

Explain keratinisation in stratified squamous epithelium

Answer 33

Stratified squamous epithelium cells can be nonkeratinized (moist) or keratinized;

Question 34

What does stratified squamous look like

Answer 34

Question 35

What is the function of stratified squamous

Answer 35

Protection against abrasion, a barrier against infection, reduction of water loss from the body

Question 36

Where are stratified squamous epithelium found ?

Answer 36

Keratinized— skin Nonkeratinized— mouth, throat, larynx, esophagus, anus, vagina, inferior urethra, cornea

Question 37

What is the structure of pseudostratified epithelium

Answer 37

Technically single layer - some cells reach the free surface others do not; Nuclei at different levels so appears stratified Almost always ciliated and associated with goblet cells (secrete mucus)

Question 38

In a pseudo-stratified epithelium what do all cells do even though it seems stratified

Answer 38

All cells touch basal layer

Question 39

What is the function of pseudo stratified epithelium

Answer 39

Synthesize and secrete mucus & move mucus (or fluid) that contains foreign particles over the surface Due to goblet cells and cilia

Question 40

Where are pseudostratified epithelium found

Answer 40

Lining of the nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, bronchi of the lungs

Question 41

How would pseudostratified epithelium be found

Answer 41

Almost always has cilia and multiple rows of nuclei

Question 42

What is the structure of transitional epithelium

Answer 42

Structure: Cuboidal/columnar when not stretched Squamous/flattenend when stretched Cell layers also decrease when stretched Eg non distended 5/6 layers to 2/3 layers

Question 43

What is the function of transitional epithelium

Answer 43

Accommodate fluctuations in the volume of fluid in organs or tubes (tolerates stretching & recoil without damage) Can withstand toxicity of urine

Question 44

Where is transitional epithelium found

Answer 44

Lining of the urinary bladder, ureters, superior urethra, pelvis of the kidney (i.e. structures where considerable expansion occurs)

Question 45

Hat does transitional epithelium look like

Answer 45

Question 46

What is the difference between transitional epithelium between when organ is empty and filled

Answer 46

Empty - thicker epithelium More layers Cells have rounded borders Filled organ- 2,3 layers Cells have become flattened and no longer rounded Resemble squamous epithelium