GI Hepatosplanchnic circulation and bile formation

Question 1

Hepatosplanchnic circulation

Answer 1

supplies blood flow to viscera (liver, stomach, small intestine, colon, pancreas, and spleen)

Question 2

oxygenated blood

Answer 2

hepatic artery (25%)

Question 3

Deoxygenated blood

Answer 3

portal vein (70%)

Question 4

Is splanchnic circulation arranged in series or in parallel to the hepatic portal circulation?

Answer 4

Series - facilitates the delivery of absorbed nutrients to the liver

Question 5

SNS - hepatosplanchnic circulation (arerioles, venuoles, veins)

Answer 5

a1 receptors - constriction of vascular smooth muscle in arterioles venules and veins

Question 6

PNS- hepatosplanchnic circulation (arterioles, venules, veins)

Answer 6

Parasympathetic increases contraction and secretion of the GI tract creating vasoactive metabolites

Increased vagal stimulation creates and increase in vasoactive metabolites which causes vasodilation and increased blood flow (SECONDARY to contractile and secretory effects)

Question 7

PNS on salivary glands

Answer 7

Vasodilation

Question 8

Myogenic vasoconstriction

Answer 8

response to sudden increase in profusion pressure

increases local vascular resistance in order to protect the capillaries from high systemic pressures and excess fluid filtration

Question 9

intrinsic response to low profusion pressure

Answer 9

low profusion results in decreased blood flow and decreased substrate delivery = accumulation of locally produced metabolic factors

metabolic factors can cause vasodilation and increase blood flow

Question 10

increased secretory activity leads to increased _____ blood flow

Answer 10

mucosal

Question 11

increased motor activity to the gut leads to increased ______ blood flow

Answer 11

muscularis

Question 12

Escape phenomenon

Answer 12

sympathetic stimulation causes constriction of both arterioles and veins resulting in decrease in splanchnic flow (fight or flight - shunted away from the gut)

Despite continued stimulation the splanchnic arterioles (NOT veins) will spontaneously vasodialate (i.e escape)within a matter of minutes

Attempt to avoid counter current exchange and save the gut from necrosis

Question 13

Counter current exchange

Answer 13

oxygenated blood dissolved in the plasma shunts from the arteriole to the venule without reaching the capillaries.

This gets exaggerated in states of low blood flow (ischemia) due to slowed blood flow velocity- risk necrosis to the villous tip

Question 14

Primary Bile acids

Answer 14

from salts or newly synthesized by hepatocytes

Cholic Acid and Chenodeoxycholic Acid

Question 15

Secondary Bile Salts

Answer 15

formed from the action of bacteria in the digestive tract

deoxycholic acid and lithocholic acid

Question 16

Bile Pigments

Answer 16

senescent red blood cells (degraded by reticuloendothelial cells- hgb is broken down to form bilirunin)

the bilirubin is removed form the plasma by the liver and is conjucated and secreted into bile

BILE PIGMENTS ARE NOT PART OF THE MICELLE

Question 17

What determine whether bile flows into the gallbladder or into the duodenum

Answer 17

resistance at the sphincter of Oddi

Question 18

Vagal stimulation and CCK cause ____ of the gallbladder and ____ of the sphincter of Oddi

Answer 18

contraction

relaxation

Question 19

presence of fats and partially digested proteins in the duodenum will cause the release of what gastrointestinal regulatory stubstance

Answer 19

CCK

Question 20

What is the mechanism of concentration of bile in the gallbladder

Answer 20

absorption of water from the gallbladder (NaCl pumped out into intracellular lumen and water follows)

water and electorlyes are then moved into capillaries by hydrostatic pressure

Question 21

where are bile salts absorbed

Answer 21

Ileum