Epithelial Cells and Surface Specialisation

Question 1

What is the main difference between mucous and serous membrane?

Answer 1

Mucous membrane are open to the exterior.

Serous membranes line certain closed body cavities (spaces which do not open to the exterior) and also envelop viscera.

Question 2

What do mucous membranes line?

Answer 2

E.g.
GI - tract
Urinary tract
Resp. tract

Question 3

What do serous membranes line?

Answer 3

The peritoneum (envelops many abdominal organs)
Pleural sacs (envelop lungs)
Pericardial sac (envelops heart)

Question 4

What do mucous membranes consist of?

Answer 4

Epithelium lining the lumen of a tube
An adjacent layer of connective tissue often referred to as the lamina propria
A third layer consisting of smooth muscle cells called the muscularis mucosae

Question 5

What do serous membranes consist of?

Answer 5

A simple squamous epithelium (mesothelium) that secretes watery lubricating fluid.
A thin layer of connective tissue that attaches the epithelium to the adjacent tissue.

Question 6

The gut, heart and lungs are all lined with serous membrane. How many parts of serous membrane do each consist of?

Answer 6

Two, one inner and one outer.

Question 7

What is the outer serous membrane called?

Answer 7

The parietal serosa

Question 8

What is the inner serous membrane called?

Answer 8

The visceral serosa

Question 9

How can the two parts of a serous membrane be explained concerning the heart for example?

Answer 9

With a balloon analogy. The heart is pushed into a blown up balloon without opening up the balloon. This means that there is one membrane touching the heart, and one lining the outside.

Question 10

Why is the parietal serosa important concerning the heart and lungs?

Answer 10

It provides frictionless movement so the heart and lungs do not rub against each other.

Question 11

Define epithelia.

Answer 11

Sheets of contiguous cells of varied embryonic origin that cover the external surface of the body and also line internal surfaces, including the body’s vessels.

Question 12

What are the embryologic origins of epithelia?

Answer 12

Ectoderm (epidermis)
Endoderm (inner and outer lining of GI - tract)
Mesoderm (inner linings of body cavities)

Question 13

What are the two big classifications of epithelial cell types? What is the difference between them?

Answer 13

Simple and stratified.

Simple is one cell layer thick and stratified is multiple cell layers thick.

Question 14

What are the four subtypes of simple epithelial cells?

Answer 14

Simple squamous
Simple cuboidal
Simple columnar
Pseudostratified

Question 15

What are the four subtypes of stratified epithelial cells?

Answer 15

Stratified squamous
Stratified cuboidal
Stratified columnar
Stratified transitional

Question 16

Where can you find simple squamous and what are its functions?

Answer 16

Body cavities like serous of lungs, heart and viscera. Important for tissue lubrication.
Material exchange.
You can also find simple squamous in capillaries which means that fast material exchange is important here.
Works as a barrier in the brain and CNS.

Question 17

Where can you find simple cuboidal and what are its functions?

Answer 17

Lining pancreatic duct and also lining thyroid gland follicles, also lines the collecting ducts of the kidney.
Allows for absorption and secretion.
Absorption and conduit
And also hormone synthesis, storage and mobilisation (thyroid)

Question 18

Where can you find simple columnar and what are its functions?

Answer 18

Lining the crypts of Lieberkühn in the mucosa of the colon. Essentially found in the colon.
Lines the villi of the small intestine as well.
Also stomach lining and gastric glands.
Functions such as absorption of nutrients and secretion.
Lubrication.

Question 19

Where can you find pseudostratified and what are its functions?

Answer 19

Upper resp. tract and trachea.
Mucous secretion
Consist of goblet cells and cilia as well.
Goblet cells secrete a viscoelastic mucous blanket which immobilise particles. The cilia traps them as well and brings the particles back up the pharynx to be swallowed instead.

Question 20

Where can you find non-keratinised stratified squamous and what are its functions?

Answer 20

Wherever you can put your finger except for 'skin'.
Oral cavity
Oesaphagus
Vagina
Part of anal canal
Surface of cornea
Inner surface of eyelid
Protects against abrasion
Reduces water loss but remains moist

Question 21

Where can you find keratinised stratified squamous and what are its functions?

Answer 21

The epidermis of the skin. It is stratified squamous with a layer of keratin on the surface.
Greatly reduces water loss and ingress
Preventrs ingress of toxins
Protects against abrasion
Reduces microbial colonisation

Question 22

What are the cells called that mainly make up the stratified squamous keratinised epithelium?

Answer 22

Keratinocytes

Question 23

What other cells can be found in keratinised stratified squamous? Give 2 examples and their function.

Answer 23

Melanocytes - produce melanin which is the main pigment that gives the skin its colour
Langehans cells - mediate immune reactions e.g. allergic contact dermatitis. Also present antigens to T lymphocytes

Question 24

Where can you find stratified columnar and what are its functions?

Answer 24

Male urethra, vas deferens and also uterus.

Protection and secretion.

Question 25

Where can you find stratified cuboidal and what are its functions?

Answer 25

Sweat glands, mammary glands and salivary glands.

Protection and secretion.

Question 26

Where can you find stratified transitional and what are its functions?

Answer 26

Urinary tract. Especially the bladder.
Distensibility and protection of underlying tissue from toxic chemicals
It makes sure the urinary tract doesn’t leak.

Question 27

What parts of the body does cystic fibrosis affect?

Answer 27

Airways (mucociliary tract doesn't work properly)
Liver (disrupts digestion)
Pancreas (can't break down food)
Small intestine (constipation)
Reproductive tract (infertility)
Skin (salty sweat)

Question 28

What are the roles of Clara cells?

Answer 28

To protect bronchiolar epithelium.
Can also act as a stem cell to regenerate bronchiolar epithelium.
However Clara cells cannot regenerate themselves!

Question 29

What are the roles of microfold cells?

Answer 29

Found only in the small intestine and very close to lymphatic nodules. These are epithelial cells that are not attached to basal lamina.
Their function is to trap pathogens and other molecules present them to underlying dendritic cells.

Question 30

What are the three early stages of damage due to smoking in lungs?

Answer 30

Normal mucus layer thickens
Cilia die off
Ciliagenesis takes 2-4 days.
This means in the short term you will probably cough more.

Question 31

What are the 4 chronic stages of damage due to smoking in lungs?

Answer 31

Goblet cells and basal cells proliferate
Clara cells die
Carcinogens induce mutations and malignancy (risk of cancer)
Pneuomocytes in the alveoli die.
Fibroblasts lay down scar tissue.

Question 32

Give 5 examples of common respiratory conditions related to smoking.

Answer 32

Acute bronchitis (cough and breathlessness due to inflammation)
Chronic bronchitis (2 episodes of cough lasting 3 months or more during a 2 year period)
Emphysema (shortness of breath due to permanent widening of the airspaces, loss of elastin, no elastin no recoil.)
COPD (emphysema + chronic bronchitis)
Asthma (wheeze, shortness of breath, chest tightness and cough)

Question 33

What are the cell renewal rates of:
Trachea
Alveoli
Goblet cells
Clara cells

Answer 33

1-2 months
8 days
10 days
Never