Histology Of Epithelial Tissues

Question 1

What is the function of epithelia?

Answer 1

Cover body surfaces

Line internal cavities

Question 2

What does epithelia rest on?

Answer 2

Basement membrane of extracellular proteins (extracellular matrix)

Question 3

What does pseudostratified mean?

Answer 3

All cells in contact with basement membrane but nuclei are at different levels

Question 4

What does stratified mean?

Answer 4

Layers of cells

Question 5

What is an important feature of transitional epithelium?

Answer 5

Able to stretch and recoil back to its original shape

Question 6

Where is transitional epithelium found?

Answer 6

Urinary tract - ureters, bladder, etc

Question 7

How do epithelial cells get their nutrients?

Answer 7

Diffusion from capillaries in connective tissue

Question 8

What does keratinised mean?

Answer 8

Layer of dead/dehydrated cells

Question 9

Where are brush-border cells found?

Answer 9

Small intestine (microvilli)

Question 10

Where are ciliated cells found?

Answer 10

Respiratory tract

Question 11

What is an important function of a basement membrane in the body?

Answer 11

Acts as a sieve in the glomerulus (glomerular filtration)

Question 12

Where do most glands originate from?

Answer 12

Epithelium

Question 13

What is the difference between exocrine and endocrine glands?

Answer 13

Exocrine glands secrete into tubules (into cavities)

Endocrine glands secrete into bloodstream

Question 14

Give an example of an exocrine gland

Answer 14

Pancreas

Question 15

Do glands ever penetrate the basement membrane?

Answer 15

No

Question 16

Describe exocrine gland formation

Answer 16

Epithelium protrudes downwards

Stalk becomes a duct

Cells at the end/bottom become specialised/secretory

Question 17

Describe endocrine gland formation

Answer 17

‘Bag’ of epithelium contained within a basement membrane detaches

Bag moves down into connective tissue

Bag invaded by capillaries

Question 18

What are the simple types of exocrine glands?

Answer 18

Tubular

Acinar

Question 19

What are the three mechanisms of exocrine secretion?

Answer 19

Merocrine

Apocrine

Holocrine

Question 20

What is merocrine secretion?

Answer 20

Secretory vesicles fuse with cell surface membrane and secretory product is discharged

Question 21

What function is related to merocrine secretion?

Answer 21

Digestion

Question 22

What is apocrine secretion?

Answer 22

Part of apical cytoplasm is lost with secretory product

Question 23

What function is related to apocrine secretion?

Answer 23

Sweating

Question 24

What is holocrine secretion?

Answer 24

Breakdown and discharge of entire secretory cell

Question 25

What function is related to holocrine secretion?

Answer 25

Sebum production

Question 26

What are the functions of cell junctions? (3)

Answer 26

Keep epithelial sheets tightly bound Barriers Communication

Question 27

What are the 6 types of cell junctions?

Answer 27

Focal adhesions Tight junction Adherens junction Desmosome Hemidesmosome Gap junction

Question 28

What is the function of a tight junction?

Answer 28

Prevent leakage (by sealing neighbouring cells together)

Question 29

What is the function of an adherens junction?

Answer 29

Join actin bundles between two cells

Question 30

What is the function of a desmosome?

Answer 30

Join intermediate filaments between two cells

Question 31

What is the function of a gap junction?

Answer 31

Allow passage of small, water-soluble molecules/ions between cells

Question 32

What is the function of a hemidesmosome?

Answer 32

Anchor intermediate filaments in a cell to the basal lamina

Question 33

What are the three anchoring junctions?

Answer 33

Desmosomes Hemidesmosomes Adherens

Question 34

What do anchoring junctions provide?

Answer 34

Rigidity and stability

Question 35

What proteins do desmosomes contain?

Answer 35

Cadherins

Question 36

What proteins do hemidesmosomes contain?

Answer 36

Integrins

Question 37

How do cadherin proteins bind?

Answer 37

Homophilically

Question 38

What is homophilic binding?

Answer 38

Binding to an exact copy

Question 39

What do cadherins exist as? (Molecularly)

Answer 39

Dimers

Question 40

How do anchoring junctions appear on transmission electron micrographs?

Answer 40

Thick plaque (they are electron dense)

Question 41

What proteins do adherens junctions consist of?

Answer 41

Cadherins Linking proteins Actin

Question 42

What are the two non-anchoring junctions?

Answer 42

Tight Gap

Question 43

How are tight junctions important in digestion?

Answer 43

Allows build up of concentration gradients

Question 44

What proteins does a tight junction consist of?

Answer 44

Claudin Occludin

Question 45

How do tight junctions bind?

Answer 45

Homophilically

Question 46

How small must a molecule be to pass through a gap junction?

Answer 46

<1000 Daltons

Question 47

What are gap junctions made up of?

Answer 47

Connexons

Question 48

What are connexons made up of?

Answer 48

6 connexins in a ring (channel)