lecture 23 - traffic across cells: general properties of epithelial cells Flashcards Preview

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Flashcards in lecture 23 - traffic across cells: general properties of epithelial cells Deck (39):
1

epithelial cells sit on the?

basement layer

2

2 things that epithelial tissues form a barrier between

- between body and external environment - between organs

3

burn victims are fucked because?

easily get infections and loose water because they have lost the epithelial tissue barrier between body and external environment (skin)

4

why is it necessary for epithelial tissues to undergo constant and rapid repair?

because they are subject to physical breakdown and injury

5

reasons epithelial tissues are important

- protection - filtration - secretion - absorption - excretion - neuroendocrine functions

6

2 types of epithelial tissue and their features

- covering and lining epithelium: skin epidermis, lining of blood vessels, lining of respiratory, urinary and GI tract - glandular epithelium: secretory portion of glands (thyroid, adrenal, sweat)

7

simple = ? important for?

1 cell layer thick, important for absorption and secretion

8

stratified =?

many cell layers thick

9

pseudostratified = ?

1 cell layer thick, however not all cells reach the apical surface

10

squamous = ?

flat

11

cuboidal = ?

cube shaped

12

columnar = ?

tall column

13

transitional = ?

shape varies with tissue streching

14

how do glandular epithelium form?

epithelial cells sink below the surface during development

15

two types of glands

1. exocrine - secretion onto free surface of epithelium 2. endocrine - secretion of hormones into blood

16

end pieces of glands consist of ______ cells, while the openings of glands are comprised of ________ cells. These two cell types have different ________ properties.

end pieces of exocrine glands consist of _acinar (secretory)_ cells, while the openings of glands are comprised of _duct_ cells. These two cell types have different _transport_ properties.

17

acinar cells function

a primary sercretion rich in organic molecules (enzymes, regulatory molecules)

18

duct cells function

modify the composition of the primary secretion by either absorbing or secreting specific ions (HCO3-, Cl-, K+, Na+)

19

what separates neighbouring epithelial cells?

paracellular space or lateral intercellular space

20

proteins of tight junctions

occludins, claudins

21

tight junctions location

most apical cell junction

22

how do tight junctions do their thang?

thin bands encircle the cell and interlock with thin bands from adjacent cells. The more bands, the tighter the junction.

23

2 functions of tight junctions:

1. a barrier to restrict movement of substance between paracellular space 2. a fence to prevent proteins from diffusing in the plane of the lipid bilayer. 2 distinct domains with different transport proteins.

24

2 distinct membrane domains set up by tight junctions

1. apical (or luminal or mucosal) membrane face lumen or of organ/cavity 2. basolateral membrane adheres to basement membrane and interfaces with the blood (includes paracellular space part)

25

amount of paracellular transport depends on...

how tight the tight junction is i.e the number of bands

26

band numbers vs. ion flow resistance

the more bands, the higher the resistance to ion flow

27

dominant transport in leaky epithelial tissues

paracellular

28

dominant transport in tight epithelial tissues

transcellular

29

direction of paracellular transport governed by...

laws of diffusion

30

tight junction resistance increases in a _________ to _________ direction in the __ tract and ______.

tight junction resistance increases in a _proximal_ to _distal_ direction in the _GI_ tract and _Kidneys_.

31

tight junction resistance in proximal end (duodenum, proximal tubule)

leaky

32

tight junction resistance in distal end (colon, collecting duct)

tight

33

in transcellular transport, how do substances move across membrane

active (primary and secondary) and passive (through ion channels) trasport

34

from lumen to blood =

absorption

35

from blood to lumen =

secretion e.g. sweat

36

entry step for absorption

apical membrane

37

entry step for secretion

basolateral membrane

38

electroneutrality refers to?

movement of ions through selectively permeable membrane will attract a counter ion

39

under EM, tight junctions appear? in freeze fracture, tight junctions appear?

In EM tight junctions appear as though the membranes have fused. In freeze fracture, it appears as interlocking network of ridges.