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

(39 cards)

1
Q

epithelial cells sit on the?

A

basement layer

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2
Q

2 things that epithelial tissues form a barrier between

A
  • between body and external environment - between organs
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3
Q

burn victims are fucked because?

A

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

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4
Q

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

A

because they are subject to physical breakdown and injury

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5
Q

reasons epithelial tissues are important

A
  • protection - filtration - secretion - absorption - excretion - neuroendocrine functions
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6
Q

2 types of epithelial tissue and their features

A
  • 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)
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7
Q

simple = ? important for?

A

1 cell layer thick, important for absorption and secretion

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8
Q

stratified =?

A

many cell layers thick

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9
Q

pseudostratified = ?

A

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

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10
Q

squamous = ?

A

flat

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11
Q

cuboidal = ?

A

cube shaped

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12
Q

columnar = ?

A

tall column

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13
Q

transitional = ?

A

shape varies with tissue streching

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14
Q

how do glandular epithelium form?

A

epithelial cells sink below the surface during development

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15
Q

two types of glands

A
  1. exocrine - secretion onto free surface of epithelium 2. endocrine - secretion of hormones into blood
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16
Q

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

A

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
Q

acinar cells function

A

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

18
Q

duct cells function

A

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

19
Q

what separates neighbouring epithelial cells?

A

paracellular space or lateral intercellular space

20
Q

proteins of tight junctions

A

occludins, claudins

21
Q

tight junctions location

A

most apical cell junction

22
Q

how do tight junctions do their thang?

A

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

23
Q

2 functions of tight junctions:

A
  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
Q

2 distinct membrane domains set up by tight junctions

A
  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.