Epithelia

Question 1

What is epithelium?

Answer 1

Layers of cells that cover body surfaces and internal/external cavities, including secretory ducts and secretory glands

Question 2

What does the epithelium sit on top of?

Answer 2

Basal lamina (part of the basement membrane)

Question 3

Define avascular

Answer 3

Not surrounded by blood vessels; epithelia rely on diffusion

Question 4

What are the apical and basal surfaces of epithelia and what does this give them?

Answer 4

Apical faces the external membrane and basal faces the basement membrane
Gives polarity

Question 5

Do epithelia have rapid regeneration?

Answer 5

yes

Question 6

Give the 7 main functions of epithelia?

Answer 6

Absorption
Surface movement
Secretion of substances
Gas exchange
Surface lubrication
Sensation
PROTECTION

Question 7

What are CAMs

Answer 7

Cell adhesion molecules - critical for adherence to underlying basal lamina and intrinsic function

Question 8

What do tight junctions do?

Answer 8

On the apical membrane which provide an absolute seal between cells to prevent solute, proteins etc from coming through

Question 9

What to adherens junctions do?

Answer 9

Connect cells together via actin filaments, which gives the internal skeleton of the cells and braces them together to give them shape

Question 10

What do gap junctions do

Answer 10

Provide small pores which solutes can be shared through between cells

Question 11

What do heavy desmosomes do?

Answer 11

At the bottom of cells and bolt them down to the basal lamina

Question 12

What do desmosomes do?

Answer 12

Connect cell to cell

Question 13

What is a single layer of epithelia called?

Answer 13

Simple

Question 14

What is a multi-layer of epithelia called?

Answer 14

Stratified

Question 15

What is pseudo-stratified epithelium?

Answer 15

Looks like it is stratified but has varying heights and is simple

Question 16

What is transitional layering?

Answer 16

multi-layered cell appearance which varies with stretch

Question 17

What shape do squamous epithelium have?

Answer 17

Flat

Question 18

What is the most common epithelia type and where can it be found?

Answer 18

Stratified squamous

Skin, oesophagus, oral cavity

Question 19

Give some examples of specialisation in epithelia

Answer 19

Proliferative
Secretary
Ciliated
Keratinised (for protection)

Question 20

Give some examples of how epithelia can be protective?

Answer 20

Prevents dehydration, chemical damage
Covers inner/outer surface,
multi layered fro strength
replaces damaged cells
tight seals between cells
keratinisation in oesophagus, vagina, skin

Question 21

What is the specialisation of epithelia in the oesophagus?

Answer 21

There are many layers for protection covered by nucleated (missing nucleus) superficial squamous cells

Question 22

How is the skin specialised for protection

Answer 22

Keratinised to prevent water loss and chemical damage

Question 23

How is the epithelial lining

of the gut specialist for absorption of nutrients?

Answer 23

Relies on cell polarity. The brush border increases the surface area to make more space for absorption

Question 24

How can epithelia be adapted for movement? Where?

Answer 24

Cilia
Airways (mucus)
Testes (Sperm)
Fallopian tube (moving egg after fertilisation)

Question 25

How is the epithelium specialised for gas exchange?

Answer 25

Single layer of squamous epithelium means a minimal distance for gaseous diffusion

Question 26

What is the difference between endothelium and epithelium?

Answer 26

Endothelium triggers blood coagulation and has a vasoactive role in vasoconstriction and dilation. It modulates smooth muscle activity and regulates inflammatory cells.

Question 27

What is mesothelium?

Answer 27

Single layer epithelium that lines all body cavities. Protein rich fluid (serous) lubricates surfaces that move against each other

Question 28

How can epithelium be modified for secretion?

Answer 28

glandular structures; ducts open onto epithelial surfaces (exocrine) glands without ducts secrete into the blood stream (endocrine)

Question 29

What is the difference between exo and endocrine glands?

Answer 29

Exocrine glands have ducts - hormones are released on the surface and lead directly to target tissue, endocrine glands don't have ducts and hormones are excreted into the blood

Question 30

What are merocrine secretions?

Answer 30

Protein product in intracellular vesicle. Vesicle membrane fuses with apical cell membrane and is released by exocytosis. Pancreatic enzymes in exocrine pancreas.

Question 31

What are merocrine secretions?

Answer 31

Protein product in intracellular vesicle. Vesicle membrane fuses with apical cell membrane and is released by exocytosis. Pancreatic enzymes in exocrine pancreas.

Question 32

What are apocrine secretions?

Answer 32

Secreted by exocytosis from the apical membrane with loss of some apical membrane Breast milk lipids

Question 33

What is holocrine secretions?

Answer 33

Secretory product accumulates in cytoplasm and the cell disintegrates to release product. Sebum in sebaceous glands

Question 34

What is ebipdermolysis bulls?

Answer 34

Blistering skin disorder Inherited Gene mutation of adhesion molecules that stick the epithelium to the basement membrane Abnormal anchoring of epidermis to dermis

Question 35

What is cystic fibrosis caused by?

Answer 35

Mutations in CFTR gene cause a defective chloride channel on apical surfaces of epithelial cells Lungs and exocrine glands in pancreas, digestive system are effected Thick mucus because less water Builds up Infection

Question 36

What is congenital ciliary dyskinesia?

Answer 36

Abnormal cilia function, cilia do not move together causing an accumulation of mucus containing diet and bacteria Ledes to lots of infection and bronchiectasis