Tissues (epithelia)

Question 1

Name the 4 main types of tissue

Answer 1

1. Epithelia
2. Connective
3. Muscle
4. Nerve

Question 2

What is the PRIMARY role of epithelia?

Answer 2

To cover surfaces

Question 3

Name the three features of epithelia that allow them to cover surfaces

Answer 3

1. No contact inhibition
2. Cell-cell junctions
3. Cell- extracellular matrix junctions

Question 4

What is meant by “no contact inhibition”

Answer 4

Contact inhibition is a process of arresting cell growth when cells come in contact with each other. As a result, normal cells stop proliferating when they form a monolayer in a culture dish.

Epithelial cells lack contact inhibition which allows them to cover surfaces

Question 5

Name the 4 different types of cell-cell junction found in epithelial cells

Answer 5

1. Tight junctions (a network of claudins and other proteins which seal adjacent epithelial cells and limit the passage of molecules and ions)
2. Desmosomes (specialized adhesive protein complexes which adhere the epithelial cell to other cells)
3. Gap junctions (channels between adjacent animal cells which enable intercellular communication)
4. Intercalated disks (adhere heart muscle cells to one another)

Question 6

Name the cell-extracellular matrix junctions which attach epithelial cells to the basement membrane

Answer 6

Hemidesmosome

Question 7

Name 5 other roles of epithelia (other than covering surfaces)

Answer 7

1. To form glands and separate compartments
2. To withstand wear and tear (thick epithelium e.g. on palms of hands)
3. To facilitate diffusion
4. Movement (cilia)
5. Absorption

Question 8

What are cilia made from?

Answer 8

Cilia are made from a 9 + 2 arrangement of microtubules

Question 9

What is epithelium?

Answer 9

The epithelia inside of structures (e.g. inside a blood vessel)

Question 10

Name the type of epithelia

Answer 10

Simple squamous epithelia

Question 11

Name the type of epithelia

Answer 11

Simple cuboidal epithelia

Question 12

Name the type of epithelia

Answer 12

Simple columnar epithelia

Question 13

Name the type of epithelia

Answer 13

Stratified squamous epithelia

Question 14

Name the type of epithelia

Answer 14

Stratified cuboidal epithelia

Question 15

Name the type of epithelia

Answer 15

Stratified columnar epithelia

Question 16

Name the type of epithelia

Answer 16

Stratified transitional epithelia

Question 17

Name the type of epithelia

Answer 17

Pseudostratified columnar epithelia

Question 18

Where are transitional epithelia found?

Answer 18

Transitional epithelia are only found in the bladder. The top layer of cells can expand and become very flat when the bladder is full.

Question 19

Provide three examples of where pseudostratified columnar epithelium would be found

Answer 19

Found in trachea and bronchi and fallopian tube

Question 20

What are glands made of?

Answer 20

Secretory epithelial cells

Question 21

Name a single celled gland

Answer 21

`Goblet cell

Question 22

Where do exocrine glands secrete into?

Answer 22

Exocrine glands secrete into tubes/ducts

Question 23

Where do endocrine glands secrete into?

Answer 23

Endocrine glands secrete into the blood

Question 24

Where do exocrine glands originate from and how do they grow?

Answer 24

Exocrine glands originate from the epithelium and grow downwards

Question 25

Name the two different types of exocrine gland

Answer 25

• Simple (tubular OR acinar)

- Compound (Tubuloacinar- both tubular and acinar)

Question 26

Name the two types of exocrine secretion

Answer 26

Mucous and serous

Question 27

What is a mucous secretion?

Answer 27

A secretion rich in proteoglycans (proteoglycan= a protein + a carbohydrate)

This secretion + water gives mucus

Question 28

What is a serous solution?

Answer 28

Serous exocrine glands secrete a watery, protein rich secretion filled with enzymes

Question 29

Name a serous exocrine gland

Answer 29

Exocrine pancreas

Question 30

Name a mucous exocrine gland

Answer 30

Mucous glands of the trachea

Question 31

Explain the three different methods of secretion

Answer 31

1. Merocrine gland remains whole and small vehicles are secreted by exocytosis into the lumen.
2. Apocrine gland- A small part of the gland containing the secretion is pinched off and secreted into the lumen
3. Holocrine gland- the whole gland containing the secretion disintegrates and becomes the secretion and then the gland regenerates.

Question 32

What is a myoepithelial cell? What is it’s function?

Answer 32

Muscular type cells that sit around the outside of the acini (round, multicellular gland) that help the secretion leave the lumen. They squeeze the acini (gland) and facilitate the release of the gland’s secretion.

Question 33

List 5 ways in which epithelial glands can function abnormally

Answer 33

• over-proliferation
• under-proliferation
• over-secretion
• under-secretion
• loss of cilia / ciliary beat