Capillary Permeability Week 5 test 2

Question 1

Cell type of capillary wall

Answer 1

single layer of endothelial cells to promote efficient exchange

Question 2

capillary exchange

Answer 2

all nutrients, gases, metabolites and water are continuously exchanged between the blood and cells

Question 3

What are the two reasons capillaries are efficient sites for gas and nutrient exchange?

Answer 3

1. blood velocity is low give adequate time to allow exchange across the membrane
2. capillaries have a HUGE surface area for gas and nutrient exchange.

Question 4

Stats on capillaries

Answer 4

more than 10 million capillaries, equivalent to about 25,000 miles of capillaries

Question 5

Diffusion

Answer 5

movement of nutrients, gas and lipid soluble substances through the semipermeable capillary wall.
**plasma proteins generally cannot cross the capillary wall

Question 6

Bulk Flow (ultrofiltration)

Answer 6

movement of protein free ECF and water soluble substances in and out through water filled pores or intercellular clefts

Question 7

Vesicular transport

Answer 7

translocation of larger, exchangeable macromolecules across capillary endothelium via vesicular trancytosis (pinocytosis, calveolae)

Question 8

4 factors that affect the rate of diffusion

Answer 8

1. faster at higher temps
2. faster with higher concentration gradient
3. faster for smaller solutes
4. slower in more viscous solutions
   * * diffusion can only occur if membrane is permeable to the solute

Question 9

difference between water soluble materials and fat soluble materials

Answer 9

water soluble materials must pass through fenestrations
eg. ions, glucose , AAs
lipid soluble can pass directly through plasma mem.
eg. gases, steroid hormones

Question 10

hydrostatic pressure and oncotic pressure operate at capillary beds to cause most of the plasmas fluid to be filtered and reabsorbed where?

Answer 10

filtration occurs at arteriolar end 20L/Day

reabsorption occurs at venous end 17 L/Day

Question 11

where does the fluid in the interstitial space go that isn’t reabsorbed in the venous side of the capillary?

Answer 11

lymphatic vessels collect excess interstitial fluid and return it to the venous bloodstream.
once in the lymphatic vessels it is called lymph

Question 12

Crystalline osmotic pressure

Answer 12

oncotic pressure due to small molecules in the plasma(mainly NaCl, Na HCO3, glucose, urea, AAs).
-since these are all water soluble their concentrations are equivalent on either side of capillary wall so there is NO EFFECT on water flow!!

Question 13

Oncotic pressure aka colloid osmotic pressure

Answer 13

osmotic pressure exerted by impermeable plasma proteins, notably albumin, in blood vessels plasma that pull water into the circulatory system from the interstitial fluid.
increases along the length of the capillary due to the proteins concentrating because they don’t filter

Question 14

hydrostatic pressure

Answer 14

force that is directed out of the capillary by a fluid pushing against the capillary wall.

Question 15

what two pressures are responsible for capillary transfers?

Answer 15

hydrostatic and oncotic

Question 16

Net filtration pressure

Answer 16

net forces pushing out - net forces pushing in
(capillary hydrostatic pressure + osmotic pressure due to interstitial fluid protein concentration) (-) (interstitial hydrostatic pressure+ oncotic pressure due to protein concentration.)

Question 17

Forces at the arteriolar end

Answer 17

hydrostatic out and osmotic in, net is out

postive value

Question 18

forces at the venous end

Answer 18

hydrostatic is out and osmotic is in, this time net is in because the osmotic pressure is higher
-negative value

Question 19

hydrostatic pressure

Answer 19

largest pressure drop is from arteries to arterioles
SM in arterioles tightly regulate BP in capillaries
pressure progressively gets lower as blood leaves capillaries to the vena cava

Question 20

capillary bed

Answer 20

branch off the metarteriole and return to the thoroughfare channel at the distal end of the bed; site of optimal exchange

Question 21

vascular shunts

Answer 21

metarteriole-thoroughfare channel connecting an arteriole directly with a postcapillary venule (bypassing true capillary bed)

Question 22

Precapillary sphincter

Answer 22

cuff of SM that surrounds each true capillary and regulates blood flow into the capillary in response to vasomotor nerves (sympathetic) and local chemical conditions, so it can either bypass or flood the capillary bed

Question 23

Vesicular transport

Answer 23

translocation of large macromolecules in a membranous sac across capillary endothelium.
eg. fluids, large solutes, Abs
**requires ATP
Vesicles can also fuse together creating pores across endothelial cells for bulk flow transport.

Question 24

Pinocytosis or Trancytosis

Answer 24

used both for endocytosis and for exocytosis
pinocytic vesicles formed at one surface of the cell may, after being detached, move through the cell to the opposite surface and there discharge their contents

Question 25

Lymphatic capillaries

Answer 25

blind-ended sacs in interstitial space
low pressure
absorb fluids from interstitial space
unidirectional
wider than blood capillaries
colorless and contain lymph

Question 26

Potential causes of edema

Answer 26

increased capillary BP
decreased plasma colloid osmotic pressure
increased capillary permeability
obstruction/disruption of lymphatics