Unique Regional Circulations

Question 1

Cutaneous circulation

Answer 1

Extrinsic control mechanisms predominate
High alpha recepto concentratio on vasculature
Low metabolic demands of the skin
Homeostatic set point : we do not want to freeze or biol
Temperature set point under hypothalamus
- changes made via modulation of sympathetic drive

Question 2

Anatomical features of skin

Answer 2

Surface area is relatively large
Blood flow can fluctuate quickly
Arterioles venous shunts allow quickly diversion of blood away form skin
Large subcutaneous venous plexus important for counter current exchange
Prolonged vasoconstriction will lead to periodic metabolic exchange

Question 3

Skeletal bed

Answer 3

Large vascular bed
Primary function is to deliver sufficient blood to muscle to meet metabolic demands
At rest both intrinsic and extrinsic regulation maintain low flow
During activation of skeletal muscle intrinsic regulation overpriced sympathetic activation

Question 4

Anatomical features of muscle vasculature

Answer 4

beta 2 receptors on skeletal muscle vasculature - vasodilation
The onset of exercise may be coupled with adrenal stimulation and epinephrine release
Mediate rapid rise in skeletal blood flow at the onset of exercise

Question 5

Coronary circulation

Answer 5

There is some sympathetic innervation to vasculature but intrinsic mechanism predominate
Low alpha receptor concentration

Question 6

Important vasodilator so far coronary circulation include

Answer 6

High CO2

Low O2, H+ and adenosine

Question 7

Cerebral circulation

Answer 7

Flow is tightly regulated - metabolic regulation predominates
Receives 20% of resting CO
Venous drainage through jugular veins with no or few valves (gravity)

Question 8

Cerebral vessels

Answer 8

Capitals density varies with Iran region
Capillaries have tight junctions forming the relativity impermeable “blood brain barrier”
- lipid soluble substances move freely
- exchange and transport mechanisms
Selected regions or “circumventricular organs” are more “leaky”

Question 9

Main controller of metabolic regulation

Answer 9

CO2

Question 10

Control of plan chic circulation

Answer 10

Metabolic and increases in food intake or a functional hyperemia
- supporting functions of the Gi tract
Rich sympathetic innervation important in shunting blood away from non vital organs during exercise or stress
May exhibit auto regulatory (metabolic) escape during prolonged constriction

Question 11

Circulation to the liver

Answer 11

Hepatic artery 30%

Portal vein 70%

Question 12

Liver

Answer 12

Portal vein does not auto regulate during prolonged constriction
Hepatic artery does auto regulate

Question 13

Ascites

Answer 13

Increased peritoneal cavity fluid
Changes in Starling forces at the level of the splanchnic bed
Right heart failure

Question 14

Ascites hepatic hypertension

Answer 14

Hepatic scarring, increased resistance to inflow
Hepatic portal venous pressure rises
Increase splanchnic capillary pressure
Increase hydrostatic filtration - fluid in body cavity

Question 15

Pulmonary circulation

Answer 15

Characteristically low resistance
Relatively large vessels throughout compares to systemic side
Vessels themselves are more compliant
Respond to increase in perfusion pressure with a decrease in resistance

Question 16

Characteristics of the pulmonary circulation

Answer 16

During increased cardiac output there may be considerable recruitment of closed capillaries
Uniquely, hypoxia triggers vasoconstriction vs vasorelaxatio observed in systemic vasculature
Mechanism unknown, shunts blood away under ventilated regions of lung
High altitude may cause pulmonary hypertension