lecture 4 - epithelia

Question 1

determinants of permeability in relation to passive diffusion

Answer 1

distance, partition coefficient and diffusion coefficient

Question 2

passive diffusion permeability =

Answer 2

(partition coefficient x diffusion coefficient) / distance

Question 3

what does Lp stand for

Answer 3

hydraulic water permeability

Question 4

epithelial tissues

Answer 4

line all external and internal surfaces

Question 5

endothelium is exposed to internal environment

Answer 5

epithelium is exposed to external environment

Question 6

simple squamous

Answer 6

function: absorption, filtration, minimal barrier to diffusion
location: capillaries, alveoli, abdominal and pleural cavities

Question 7

simple cuboidal

Answer 7

function: secretion, transportation
location: glands and ducts, kidney tubules, ovaries

Question 8

simple columnar

Answer 8

function: absorption, protection, secretion
location: digestive tract
can be ciliated or non-ciliated

Question 9

stratified squamous

Answer 9

function: protection
location: skin, mouth, upper throat, oesophagus
can be keratinised (protected by keratin - makes them impermeable and dry e.g. skin)

Question 10

pseudostratified columnar

Answer 10

function: absorption and protection
location: upper respiratory tract, trachea

Question 11

transitional

Answer 11

function: stretchable layer
location: bladder

Question 12

tight junctions

Answer 12

membrane proteins that seal adjacent cells together
ensure molecules cannot leak freely between cells
create polarity

Question 13

tight junctions formed by

Answer 13

claudin and occludin bind to each other and form tight junctions

Question 14

tight junctions are bound by cld-1 and cld 3, leaky junctions involve

Answer 14

cld- 2 which isnt as complementary

Question 15

anchoring junctions

Answer 15

provide mechanical stability
anchor cells to the basal lamina or to other cells
categorised by the type of cytoskeletal filament they interact with:
actin attachments
cell-cell: adherens junction
cell-basal lamina: focal adhesions
intermediate filament attachments
cell-cell: desmosomes
cell-basal lamina: hemidesmosomes

Question 16

basal lamina

Answer 16

mesh work of various different proteins and collagen and it underlies all epithelial tissue
givens cells something to attach to

Question 17

basement membrane

Answer 17

combination of basal lamina and reticular lamina (layer of collagen)
allows epithelial cells to connect to tissue below

Question 18

gap junction

Answer 18

allows neighboring cells to share the same intracellular environment, allows things to diffuse easily from cell to cell

Question 19

the ussing chamber

Answer 19

measures resistance of ion transport
used to determine what ion channels are present (and their concentration/expression)

Question 20

put different concentrations of eg sodium solutions

Answer 20

if you get a reading you know there are sodium channels present

Question 21

transepithelial voltage Vte =

Answer 21

Vbl - Vap
total difference in charge across the cell (use nernst)

Question 22

what can you block potassium sodium pump with

Answer 22

ouabain

Question 23

what can you block potassium channels with

Answer 23

barium