Microcirculation (Exam IV)

Question 1

The human body has how many capillaries?
How many square meters of surface area is this?

Answer 1

• 10+ billion capillaries
• 500 - 700 sq meters surface area

Question 2

Precapillary sphincters are extensions of what?

Answer 2

Arteriolar smooth muscle

Question 3

Where do breaks in the endothelial lining of CV system occur?

Answer 3

Trick question, endothelial lining is continuous everywhere.

Question 4

What are the openings in between endothelial cells called?
What typically cannot move through these openings?

Answer 4

• Intercellular Clefts
• Proteins

Question 5

What are the three main components that comprise the interstitial fluid gel?

Answer 5

1. Collagen
2. Proteoglycan filaments
3. Hyaluronic acid (verify)

Question 6

What are free fluid rivulets?
What can cause these rivulets to become engorged?
What occurs if one of these rivulets attaches the capillary?

Answer 6

• H₂O pockets devoid of gel-qualities.
• Engorgement occurs from H₂O leaving the capillary more than it should.
• It forms a “highway” that allows for a massive amount of H₂O loss from the capillary.

Question 7

What is the intracellular volume of RBCs?
What is the blood plasma volume?
What do these two combined make?

Answer 7

• RBCs ICF = 2L
• Plasma = 3L
• Total blood volume = 5L

Question 8

Filration is the term for what?

Answer 8

Fluid movement out of a capillary.

Question 9

What is P_CAP?
What is P_ISF?
What is π_CAP?
What is π_ISF?

Answer 9

• Hydrostatic pressure of capillary
• Hydrostatic pressure of interstitial fluid
• Capillary Oncotic Pressure
• Interstitial Fluid colloid osmotic pressure

Question 10

What is oncotic pressure?
What other term could be used to name oncotic pressure?

Answer 10

• The pressure of the proteins in the capillaries that tries to pull fluid into the capillaries.
• Capillary colloid osmotic pressure.

Question 11

Which capillary pressure forces favor filtration?

Answer 11

• P_CAP
• P_ISF
• π_ISF

Question 12

Which capillary forces disfavor filtration?

Answer 12

π_CAP

Question 13

What is the arterial P_CAP?
What is the arterial P_ISF?
What is the arterial π_CAP?
What is the arterial π_ISF?

Answer 13

P_CAP = 30mmHg
P_ISF = -3mmHg
π_CAP = 28mmHg
π_ISF = 8mmHg

Question 14

How would arterial NFP (net filtration pressure) be calculated?

Answer 14

NFP = (P_CAP + P_ISF + π_ISF) - π_CAP

Question 15

Which capillary force changes when talking about the capillary forces on the venous end of the capillary beds?
How does it change?
How does this affect NFP?

Answer 15

• P_CAP changes from 30 to 10.
• NFP becomes -7. Filtration becomes disfavored

Question 16

Why does the venous end of capillary beds have less resistance than the arteriolar side?

Answer 16

• Larger surface area
• More splitting & parallel vessels

Question 17

The average capillary pressure between both arterial & venous sides of the capillary beds should be what?

Answer 17

17.3 mmHg

Question 18

What does Inulin measure?

Answer 18

Kidney function

Question 19

A higher molecular weight (MW) means what for capillary permeability? Give examples.

Answer 19

↑MW = ↓permeability (albumin & hemoglobin).

Question 20

Can lymphatic flow be increased? If so how much?
What is necessary for this?

Answer 20

• Yes by 20x
• Dependent on skeletal muscles for pumping (SCD’s would help too)

Question 21

Where does the lymphatic system drain into?

Answer 21

Subclavian Vein

Question 22

How much fluid can be filtered by the lymphatic system?

Answer 22

120 ml/hr

Question 23

What does the lymphatic system collect in addition to interstitial fluid?

Answer 23

• Bad proteins & ISF colloids

Question 24

What protein is the primary contributor to oncotic pressure?
Secondary?
Tertiary?

Answer 24

1. Albumin
2. Globulins (antibodies, immune system proteins, etc)
3. Fibrinogen

Question 25

What is the Donnan effect?
What is the result of this effect?

Answer 25

• Cations associate with negatively charged proteins which then prevent ion movement across the endothelium.
• Result: increase in π_CAP (example in lecture was 19 to 28 mmHg)

Question 26

Why might edema be seen with isolated liver failure?

Answer 26

• Decrease in π_CAP due to liver not making as many clotting factor proteins that circulate in the blood.