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GI Physiology > lecture 14 - splanchnic and hepatic circulations in health > Flashcards

lecture 14 - splanchnic and hepatic circulations in health Flashcards

1
Q

what are the exceptions to the strictly in parallel systemic circulation?

A
  • splanchnic circulation

- renal system

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2
Q

what is the cardiac output distribution at rest?

A 
GI tract and liver - 25 %
skeletal muscle - 20 % 
kidneys - 20 %
brain - 13 %
skin - 8 %
heart - 4 %
others - 10 %
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3
Q

waht percentage of cardiac output goes to the GI tract and liver?

A

25 % of CO and oxygen consumption

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4
Q

what percentage of cardiac output goes to the celiac artery and what is its blood flow?

A

10 % and 700 ml/min

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5
Q

what percentage of cardiac output goes to the superior mesenteric artery and what is its blood flow?

A

10 % and 700 ml/min

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6
Q

what percentage of cardiac output goes to the inferior mesenteric artery and what is its blood flow?

A

5 % and 400 ml/min

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7
Q

what does the celiac trunk supply?

A

stomach, spleen, and pancreas

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8
Q

what does the superior mesenteric artery supply ?

A

intestine and pancreas

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9
Q

what does the inferior mesenteric artery supply?

A

intestine

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10
Q

what is the blood flow in the hepatic artery?

A

500 ml/min

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11
Q

what is the blood flow in the portal vein?

A

1300 ml/min

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12
Q

what is the blood flow in the hepatic veins?

A

1800 ml/min

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13
Q

what is the general structure of the gut wall? list the order

A
  1. ) mucosa - epithelium
  2. ) mucosa - lamina propria
  3. ) mucosa - muscularis mucosae
  4. ) lumen
  5. ) lymphatic tissue
  6. ) duct of gland outside tract
  7. ) gland in mucosa
  8. ) submucosa
  9. ) glands in submucosa
  10. ) meissner’s submucosal plexus
  11. ) vein
  12. ) muscularis: circular muscle
  13. ) muscularis: longitudinal muscle
  14. ) serosa: areolar CT
  15. ) serosa: epithelium
  16. ) auerbach’s myenteric plexus
  17. ) nerve
  18. ) artery
  19. ) mesentry
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14
Q

where do blood vessels enter and leave the gut wall?

A

enter - at 18: the artery

leave - at 11: the vein

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15
Q

what does the microcirculation in the GI tract consist of?

A

artery, arteriole, precapilllary sphincter, capillary, venule, vein

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16
Q

blood flow to each layer (mucosa, submucosa, muscularis) is organised in ……

A

parallel

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17
Q

since blood flow is parallel, this allow blood flow to ?

A

adjust to metabolic requirments of each layer by shunting blood from one layer to another without changing the overall GI blood flow

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18
Q

over 65 % of the GI blood flwo is to the ….

A

mucosa

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19
Q

where does autoregulation of the GI tract occur?

A

-stomach, small intestine and colon

20
Q

when is autoregulation of the GI tract more prominent?

A

in the fed rather than the fasting state and in the mucosa which is metabolically more active

21
Q

blood vessels in the GI tract are heavily innervated by the …..

A

sympathetic nervous system

22
Q

what does activation of the sympathetic nervous system cause and what does this do to the body?

A

causes alpha adrenoreceptor mediated vasoconstriction which diverts blood from the GIT to the vital organs during reduction in MAP.

23
Q

during a haemorrhage, GI blood flow can be reduced to ,,,,, of resting glow follow ….. activation

A
  • 25 %

- SNS

24
Q

what does vasoconstriction of the arterioles and veins in the GI cause?

A
  • blood is pushed back from veins in GI to IVC increasing circulating blood volume
  • vasoconstriction of arterioles in GI increases blood pressure (TPR)
25
Q

the liver is an …… organ in which …. quantities of blood can be stored in its blood vessels

A
  • expandable/compressable

- large

26
Q

what is normal liver blood volume?

A

500 ml or 10 % of total blood volume

27
Q

the liver is capable of acting as a ….. in times of excess blood and is capable of supply extra blood in times of ……

A
  • blood reservoir

- reduced blood volume (hypovolaemia)

28
Q

in cardiac failure, the blood volume in the liver can rise to?

A

1 L when right atrial pressure rises

29
Q

in times of circualtory stress, the SNS causes …….. of ….. and a large volume of blood is discharged into the systemic circualtion within …..

A
  • vasoconstriction of the hepatic veins

- 1-4 mins

30
Q

in normal humans the volume of blood mobilised can be as much as ….

A

350 ml

31
Q

what is hypoperfusion?

A
  • arterial flow flows into the villus in an opposite direction to venous flow that goes out the villus.
  • Sometiems blood O2 is transported from arteriole to venule via capillaries, without the help of being carried by the tip of the villus.
  • Usually this wouldn’t effect the villus but in circualtory shock, cells in the tip of the villus can become ishaemic and die.
32
Q

as much as ….. of O2 can take a short circuit (countercurrent blood flow)

A

80 %

33
Q

what can happen in severe hypoperfusion of the GI tract?

A

it is not tolerated for long because there is a disruption of the mucosa which reduces barrier function;

  • endotoxin (lipopolysaccharide) can enter sytemic circulation
  • endotoxin can induce multiorgan failure and circualtory shock (septic)
34
Q

what happens after the ingestion of a meal to GI blood flow?

A

it can increase 6 fold

35
Q

what are the mechanisms that are involved in gastric mucosal blood flow?

A
  1. ) metabolic vasodialtion ( adenosine)

2. ) dilator action of GI hormones and neurotransmitters (CCK, vasoactive intestinal peptide, gastrin, secretin)

36
Q

what does vasoactive intestinal peptide do and where is it released from?

A
  • it is a neurotransmitter released from parasympathetic, cholinergic nerves
  • acts on smooth muscle and glands
  • relaxes sphincters and increases pancreatic and intestinal secretion
37
Q

what does CCK do?

A
  • it is a hormone that acts on pancreas, gallbladder and stomach
  • increases enzyme secretion, contracts gallbladder, increases gastric emptying
38
Q

what does gastrin do?

A
  • it is a hormone that acts on the stoamch and increases gastric acid secretion
39
Q

what doe secretin do?

A
  • it is a hormone that acts on the stomach and pancreas

- it releases bicarbonate and pepsin

40
Q

total liver blood flow?

A

1.5 L/min (1-2)

41
Q

portal venous blood is partly ….

A

de oxygenated

42
Q

portal venous blood flow is ….. of total liver blood flow

A

70-80 %

43
Q

what is portal venous pressure?

A

5-10

44
Q

where do hepatic arterial and portal venous blood flow meet?

A

in the hepatic sinusoid

45
Q

sinusoids are lined with a layer of …… whihc are clusters of ….. . This makes it ….. and allows …. to pass through it

A
  • endothelial cells
  • fenestrae
  • leaky and allows plasma proteins

GI Physiology (16 decks)

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