L21 Special Circulation: Cutaneous & Splanchnic

Question 1

Primary function of cutaneous circulation

Answer 1

To regulate temperature.

Human body is better at losing heat than conserving it

Question 2

Apical vs. Non-apical skin and BF

Answer 2

Apical Skin: (At apexs of the body)

• LOW BF
• contains Glomus bodies (special AV anastomoses) to help heat loss
• high SA:Vol. ratio
• NO sweat glands
• fingertips, nose, ears, toes, lips, etc.
• innervated by: NE, constriction —- when at rest, remove Symp stimulation - dilation

Non-apical Skin:

• HIGH BF
• no AV anastomoses
• SWEAT GLANDS
• innervation: Active vasodilation via *Sympathetic cholinergics *(Ach)

Question 3

Thermic factors that regulate BF

Answer 3

The most important regulator of BF to your skin is your core body temperature.

If your core temp is LOW, you will vasoconstrict to prevent heat loss

If your core temp is HIGH, you will vasodilate to dissipate heat.

Abnormal condition: if it’s super hot outside, you vasodilate all over the place to increase heat loss. If you get injured, and start hemorrhaging, your blood will go out much faster. Your baroreceptor response will kick in to constrict vessels and prevent more loss, but since it’s super hot outside your body temp is telling you to dilate. Competition between constricting and dilating results in less constriction – making hemorrhage more dangerous

Question 4

Anatomy & Function of splanchnic circulation

Answer 4

Generally get 25% of CO

Celiac, SMA, IMA are major vessels.

small vessels in the villi of the intestinal lumen are responsible for countercurrent flow system:

This is when Na or other solutes absorbed in the capillaries from intestinal lumen pass into the venule but then diffuse over back into the arteriole, this increasing the osmolarity and inceasing H₂O absorption and BF

Portal vein takes blood from organs to the Liver. Hepatic veins take blood from the liver and dump it into the IVC
This connected system can lead to ascites:

RV backed up –> RA –> IVC –> liver can be cirrhosis –> portal vein backed up –> increased P in organs –> fluid pushed OUT of organs –> abdominal edema/ascites.

Can also back up the P in esophageal, rectal and stomach veins - leading to varices and hemorrhage if they burst

Question 5

Metabolic regulation of splanchnic BF

Answer 5

When metabolism increases, more O2 is needed. More metabolites are produced and thus vasodilation is seen. vasodilation = increased BF
Tissue compression during peristalsis can compress vessels and limit BF - prolonged ischemia presents as a cramp

Digestion = vasodilation

Question 6

Neural regulation of splanchnic BF

Answer 6

Sympathetic: vasoconstriction via NE on alpha receptor
(decrease BF so you can send it somewhere else - direct inn. on vasculature)

dilation also seen via NE on beta receptors

Exercise or stress - fight or flight - shift blood from here to other parts of body - if too long, bowels can undergo ischemia

Parasympathetic: rest and digest - more intestinal motolity increases BF, therefore cause vasodilation and increase in BF (increase BF via digestion, no direct innervation)

How much BF goes to your intestines is largely determined by what you eat.
fats and carbs = more BF to digest