Lectures 19 & 20: Capillary Fluid Exchange and Lymph Flow

Question 1

What is another name for colloid osmotic pressure?

Answer 1

oncotic pressure

Question 2

What is the difference between osmotic pressure and coilloid osmotic (oncotic) pressure?

Answer 2

Osmotic pressure is the pressure exerted by all solutes in a solution, while oncotic pressure is the pressure exerted by proteins only

Question 3

What would happen to net filtration pressure if capillary hyrdostatic pressure increased?

Answer 3

it would increase

Question 4

What would happen to net filtration pressure if capillary oncotic pressure decreased?

Answer 4

It would increase because you are decreasing one of the driving forces (proteins) that is keeping the fluid in the capillary

Question 5

What are the four primary forces driving fluid exchange ?

Answer 5

1. capillary hydrostatic pressure (weight of the fluid)
2. Interstitial fluid colloid osmotic pressure (oncotic pressure)
3. Interstitial fluid hydrostatic pressure (weight of the fluid in the interstitial)
4. Capillary colloid osmotic pressure (oncotic pressure)

Question 6

What does the capillary hydrostatic pressure (the weight of the fluid do)?

Answer 6

Tends to force fluid outward through the capillary membrane

Question 7

What is oncotic pressure primarily determined by?

Answer 7

concentration of proteins

Question 8

What does the Interstitial fluid colloid osmotic (oncotic) pressure cause?

Answer 8

osmosis OUT of capillary

Question 9

What does capillary colloid osmotic (oncotic) pressure cause?

Answer 9

osmosis INTO the capillary

Question 10

Normally, what is the Interstitial fluid hydrostatic pressure (weight of the fluid in the interstitial)?

Answer 10

close to zero

Question 11

At the arterial side of capillaries, what is favored?

Answer 11

net filtration

Question 12

At the venous side of capillaries, what is favored?

Answer 12

net reabsorption

Question 13

Why are different things favored at the arterial vs the venous side of capillaries?

Answer 13

Because there is a 15-25mmHg difference in capillary hydrostatic pressure between arterial end and venous end

Question 14

What carries away any remaining fluid that’s in the interstitium?

Answer 14

the lymphatic system

Question 15

What can occur if the rate of fluid that enters in the interstitium is greater than what the lymphatic system can remove?

Answer 15

Edema

Question 16

Every cause of edema can be related to one or more of the following (4):

Answer 16

1. Increased capillary hydrostatic pressure
2. increased capillary permeability
3. decreased plasma oncotic pressure
4. lymphatic obstruction

Question 17

Why doesn’t fluid accumulate in the interstitial space if filtration pressure exceeds reabsorption?

Answer 17

Most of the fluid that is filtered out of the capillary is reabsorbed while the small remaining portion is returned to circulation via the lymphatic system

Question 18

What is the normal rate of net filtration in the whole body?

Answer 18

2ml/min or 2-3L/day so this is the amount that is returned to circulation via lymphatic system each day

Question 19

What does the lymphatic system do?

Answer 19

returns interstitial fluid back to circulation

Question 20

What happens to proteins that are leaked out of capillaries?

Answer 20

they are removed from the interstitial space and put back into circulation… this keeps interstitial fluid colloid osmotic pressure low and this is the only way that proteins in the interstitial space can be removed

Question 21

What two factors affect lymph flow?

Answer 21

1. Interstitial fluid pressure

2. activity of a lymphatic pump

Question 22

As interstitial fluid pressure rises, what happens to lymph flow?

Answer 22

it increases

Question 23

What is an example of a lymphatic pump?

Answer 23

contraction of muscles surrounding lymph vessels and movement of body parts (increase lymph flow)