Quiz 7- Microcirculation and Lymphatics, Local control of Blood Flow

Question 1

Name 3 endogenously found vaso-constricting substances.

Answer 1

Catecholamines (Epinephrine, norepinephrine, dopamine), Endothelin, Serotonin, Angiotensin 2, Vasopressin. (Slide 5 or Guyton, pg. 199)

Question 2

Name 3 endogenously found vaso-dilating substances.

Answer 2

Histamine, adenosine, Nitric Oxide, carbon dioxide, potassium, hydrogen ion, prostaglandins, acetylcholine, bradykinin. (Slide 5 or Guyton, pg. 193)

Question 3

What is the Metabolic Mechanism?

Answer 3

Metabolic Mechanism: Intervention that results in an inadequate oxygen (Nutrient) supply for the metabolic requirements of the tissues results in the formation of vasodilator substances which increase blood flow to the tissues (Slide 7, Guyton, pg. 194, Klabunde, pg. 150)

Question 4

What is the Myogenic Mechanism?

Answer 4

When the lumen of a blood vessel is suddenly expanded, the smooth muscles respond by contracting in order to restore the vessel diameter and resistance. (Slide 19, Guyton, pg. 194, Klabunde, pg. 153-154)

Question 5

What is Reactive Hyperemia?

Answer 5

The transient increase in organ blood flow that occurs following a brief period of ischemia, usually produced by temporary arterial occlusion (Slide 10, Klabunde, pg. 156).

Question 6

What is Autoregulation?

Answer 6

The intrinsic ability of an organ to maintain a constant blood flow despite changes in perfusion pressure. (Slide 15, Klabunde, pg. 154)

Question 7

Name 3 endothelial factors that help regulate blood flow?

Answer 7

Nitric Oxide (vasodilator),
Prostacyclin (vasodilator),
Endothelial-derived hyperpolarizing factor (EDHF) (vasodilation),
Endothelin (vasoconstrictor).
(Slide 23, Guyton, pg. 195, Klabunde, pg. 152-153)

Question 8

What is nitric oxide?

Answer 8

Most important in terms of regulating blood flow under normal physiolic conditions. Generated from amino acid L-arginine to synthesize nitric oxide synthase (NOS). From the endothelial cell to the smooth muscle cells where it binds to and activates intracellular guanylyl cyclase to form cGMP relaxing smooth muscle (Slide 26, Klabunde, pg. 152)

Question 9

Is Endothelin a vaso-dilator or -constrictor?

Answer 9

Potent Vasoconstrictor (Slide 34, pg. 152)

Question 10

Why are blood vessels prone to vaso-constriction, vaso-spasm and thrombosis when the endothelium is damaged?

Answer 10

This is due to the decrease of nitric oxide and prostacyclin production and an increase endothelin production causing vasoconstriction, vasospasm, and thrombosis. (Slide 36, Guyton, pg. 196).

Question 11

What substance is responsible for this Metabolic Mechanism?

Answer 11

Substances responsible for this mechanism: Adenosine, Potassium ions, Carbon Dioxide, Hydrogen ion, Lactic acid, and inorganic phosphate. (Slide 9, Klabunde, pg. 150)

Question 12

Give a common clinical example of Reactive Hyperemia.

Answer 12

Example are tourniquet to a limb, arterial vessels clamped and released later in surgery, transient coronary occlusion. (Klabunde, pg. 154)

Question 13

What mechanism of blood flow regulation is thought to be involved in autoregulation?

Answer 13

Mechanisms involved are myogenic and metabolic (Slide 15, Klabunde, pg. 154)

Question 14

How might nitric oxide be helpful during one-lung ventilation?

Answer 14

The inhaled nitric oxide is delivered only to ventilated alveoli. This improves V/Q relations by vasodilating capillaries and improving blood flow to areas participating in gas exchange. (Slide 29-30, Klabunde, pg. 152)

Question 15

What is capillary filtration?

Answer 15

Net movement of fluid or H2O out of the capillary

Question 16

What is capillary reabsorption?

Answer 16

Movement of fluids or H2O back into the capillary

Question 17

What are the Starling Forces with regards to capillary filtration/reabsorption?

Answer 17

• Increased capillary pressure and interstitial fluid osmotic pressure will move fluid out of the capillary.
• increased Plasma colloid osmotic pressures and interstitial fluid hydrostatic pressure cause inward movement of fluids

Question 18

What is osmosis?

Answer 18

Water moves from areas of high H2O concentration to areas of low H2O concentration through a semipermeable membrane.

Question 19

If Net Driving Forces are POSITIVE, does it favor capillary filtration or reabsorption?

Answer 19

Filtration

Question 20

Are hydrostatic pressures within the capillary equal at the arteriolar end and the venous end?

Answer 20

No, pressures are higher at the arteriolar side and lower at the venous side. Arteriolar side ~ 30mmHg and Venous side ~ 10mmHg

Question 21

Under normal circumstances, what Net Driving Force favors fluid movement INTO the capillary?

Answer 21

Negative pressures (<0)

Question 22

What would the Net Driving Forces be in a patient with congestive heart failure? Would they favor filtration or reabsorption?

Answer 22

They would have increased capillary hydrostatic pressure will lead to filtration

Question 23

What is the function of the lymphatic system?

Answer 23

Move excess fluids, fat, protein, albumin back into the circulation

Question 24

How is plasma filtrate returned to the circulation by the lymphatic system?

Answer 24

Through tissue pressure, intermittent skeletal activity, lymphatic vessel contractions and one-way valves

Question 25

What is the thoracic duct? Where is it found and what does it connect to?

Answer 25

Thoracic duct is part of the lymphatics where all lymph from the Left head, left arm and all lower body will empty. It is found in the posterior chest and is connected to Left Internal jugular and Left subclavian (empties back into circulation).

Question 26

What things may cause edema?

Answer 26

Lymphatic obstruction
Changes in capillary permeability
Reduced Plasma protein
increased capillary hydrostatic pressure