Circulatory 4

Question 1

Precapillary resistance vessels

Answer 1

Arterioles, metarterioles, and precapillary sphincters

Question 2

Exchange vessels

Answer 2

Capillaries

Question 3

Postcapillary resistance vessels

Answer 3

Venules

Question 4

Five characteristics of capillary blood flow

Answer 4

1. Low velocity
2. Vasomotion
3. Pressure gradients
4. Non-uniform
5. Rouleaux formation

Question 5

Transcapillary fluid exchange

Answer 5

Movement of fluid, exchange of nutrients, out of and into the capillary

Question 6

Factors governing transcapillary fluid exchange

Answer 6

1. Plasma oncotic pressure
2. Capillary hydrostatic pressure
3. Tissue oncotic pressure
4. Interstitial hydrostatic pressure

Question 7

Plasma oncotic pressure

Answer 7

An osmotic pressure exerted by substances found int he plasma, primarily plasma proteins

Question 8

Capillary hydrostatic pressure

Answer 8

Mean capillary blood pressure

Question 9

Tissue oncotic pressure

Answer 9

An osmotic pressure exerted by substances dissolved in the intersitium, such as proteins. Counterpart to plasma oncotic pressure

Question 10

Interstitial hydrostatic pressure

Answer 10

Hydrostatic pressure caused by the volume of fluid within the interstitium

Question 11

Determinants of plasma oncotic pressure

Answer 11

The key factor that holds fluid within the capillaries is the osmotic pressure of the plasma proteins

Question 12

Most clinically relevant protein

Answer 12

Albumin

Question 13

Why is that protein the most clinically relevant?

Answer 13

Albumin exerts a greater osmotic force than can be accounted for solely on the basis of the number of molecules dissolved in a unit volume of plasma (contributes a disproportionately large percentage of the plasma oncotic pressure)

Question 14

With what does albumin interact?

Answer 14

Negatively charged ions, such as chloride, resulting in the retention of more sodium within the vascular space

Question 15

Breakdown of proteins in plasma

Answer 15

Albumin - 51%
Globulin - 17%
Fibrinogen - 4%
Others - 28%

Question 16

Determinants of capillary hydrostatic pressure: bathtub analogy

Answer 16

Amount of water filling a tub (capillary hydrostatic pressure) is determined by the resistance to water flow entering the tub through the faucet (precapillary resistance to arterial flow) and resistance to water flow leaving the tub through the drain (post-capillary resistance to venous flow)

Question 17

What determinant plays the biggest part in capillary hydrostatic pressure?

Answer 17

Venous pressure; there is significant pre-capillary resistance on the arterial side, and little post-capillary resistance

Question 18

Pre/post-capillary resistance ratio

Answer 18

Increase it: decrease capillary hydrostatic pressure

Decrease it: increase capillary hydrostatic pressure

Question 19

Prostacyclins

Answer 19

Increase cAMP to phosphorylate myosin light chain kinase, inhibiting MLCK. Decreased phosphorylation of MLC, less actin-myosin interaction
VASODILATION

Question 20

Endothelium-derived relaxing factor

Answer 20

Vasodilation, consisting of primarily nitric oxide

Question 21

Nitric oxide

Answer 21

Acts via cGMP/PKG to phosphorylate MLCK, inhibiting MLCK, decreasing MLC phosphorylation and thereby decreasing actin-myosin interaction.
VASODILATION

Question 22

Endothelin

Answer 22

ET receptors on vascular smooth muscle cells activate PLC to release IP3, which releases intracellular calcium
VASOCONSTRICTION

Question 23

Metabolites

Answer 23

Adenosine, hydrogen ion, carbon dioxide, and potassium ion

Cause relaxation and vasodilation

Question 24

Function of the lymphatic system

Answer 24

Collect and return interstitial fluid to the circulatory system

Question 25

Structure of lymphatic vessels

Answer 25

Unidirectional flow of plasma and protein Valvular, like veins, but have thinner walls Non-fenestrated, no muscle

Question 26

Where do lymphatic vessels eventually end up?

Answer 26

In large collecting vessels that return the lymphatic fluid to the subclavian veins

Question 27

Three factors governing lymph flow

Answer 27

Amount of capillary filtration Skeletal muscular activity Lymphatic unidirectional valves

Question 28

Edema

Answer 28

An accumulation of excess fluid within the interstitial space

Question 29

Precipitating factors of peripheral edema

Answer 29

1. Reduction in plasma protein concentration 2. Increase in capillary hydrostatic pressure 3. Increased permeability of capillary membrane 4. Lymphatic obstruction

Question 30

Possible causes of edema

Answer 30

1. Congestive heart failure 2. Mechanical obstruction of venous return 3. Renal disease - loss of protein 4. Liver disease - lack of protein 5. Burn - increases capillary permeability