Regulation of Interstitial Fluid Volume

Question 0

Interstitial fluid flow

Answer 0

microvascular filtration -> Interstitial space -> lymph flow -> circulatory system

microvascular filtration -> Interstitial space -> serosal transudation -> lymph flow -> circulatory system

Question 1

Interstitial Space

Answer 1

b/n vascular space & cells. contains interstitial fluid and extracellular matrix (collagen, elastin, hyaluronan & glyocsaminoglycans)

a gel w/ small free fluid channels

Question 2

In most capillary beds under normal conditions,

Answer 2

reabsorption does not occur

Question 3

Interstitial Fluid Pressure

Answer 3

Sub-atmospheric (in many tissues like lung, subq tissue, resting sk. m.)
~occurs because of active fluid drainage
Supra-atmospheric (heart, liver, kidney, contracting sk. m)
~always helps drive fluid out of tissue

Question 4

Interstitial Protein concentrations

Answer 4

Thoracic duct ~75%
Liver ~100%
CNS ~1%
Full complement of clotting factors

Sum interstitial protein > sum of plasma protein

Question 5

Pressure-Interstitial Volume Relationship

Answer 5

depends on the tissue:
-lung & subq tissue = low volume, low P
-heart & kidney = high volume, high P
(directly related!)

Question 6

When does interstitial P ^?

Answer 6

as interstitial volume ^

Question 7

How does an increase in venous pressure reduce microvascular filtration?

Answer 7

^ venous P drives fluid into interstitial space => ^ interstitial V => ^ interstitial P => reduced filtration because the hydrostatic and colloid P difference is less.

the ^ interstitial P brings filtration back towards normal but at a higher interstitial V.

Question 8

Anti-edema Mechanisms

Answer 8

1. Increased interstitial fluid P
2. Increased lymph flow (10x or more)
3. Decreased intersitial COP via protein wash-down & ^ lymph flow
4. Increased serosal transduation

Question 9

How does increased interstitial P reduce edema?

Answer 9

it enhances fluid removal

Question 10

Lymphatic vessel structure

Answer 10

-endothelium, basement membrane, little bit of sm. m., one-way valves, perfused & innervated (large ones)

Question 11

Lymphatic vessels act as pumps b/c of

Answer 11

their one-way valves & sm. m.

Question 12

How does Load-Dependence of the heart work?

Answer 12

contractions ^ strength => ^ stroke volume => ^ freq. of contraction => ^ flow

Question 13

Lymphatic Response to increased Atrial P

Answer 13

increases lymph flow significantly

Question 14

Microvascular protein flow =

Answer 14

protein flow into interstitial space

Question 15

Protein Washdown

Answer 15

When fluid filtration increases, total protein increases b/c of diffusion but protein concentration decreases.

Question 16

Net effect of Protein Washdown

Answer 16

decrease in interstitial protein concentration

Question 17

Interstitial Protein Concentration vs. Microvascular Filtration

Answer 17

inversely proportional.
high interstitial [protein] = low filtration rate
low interstitial [protein] = high filtration rate

Question 18

What happens if edema happens again and the anti-edema mechanisms are already taking place?

Answer 18

edemas would suddenly start popping up everywhere.

to help: give colloid solution or give hypertonic saline

Question 19

Anti-edema mechanisms purpose

Answer 19

to help reduce likelihood of edema

Question 20

Serosal Transudation

Answer 20

flow from interstitial space across serosal surface to surrounding cavity

Question 21

When does transerosal flow increase?

Answer 21

with edema formation

Question 22

Potential Space drainage

Answer 22

• occurs via lymphatic system
• lymphatic stomata (how it goes away)
• doesn’t filter across a membrane
• not reabsorbed into the vascular space

Question 23

All anti-edema mechanisms are

Answer 23

interconnected!