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Systems 1 > Physiology of Absorption in stomach and intestines > Flashcards

Physiology of Absorption in stomach and intestines Flashcards

(85 cards)

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1
Q

What 3 main arteries come off the abdominal aorta?

A
  • Celiac artery
  • Superior mesenteric artery
  • Inferior mesenteric artery
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2
Q

Celiac artery supplies what?

A

Stomach and pancreas

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3
Q

What does the superior mesenteric artery supply?

A

Pancreas, SI, LI

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4
Q

What does the inferior mesenteric artery supply?

A

Transverse and descending colon plus rectum

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5
Q

In the liver, the blood flows from two different
sources, this will establish an

A

an oxygen gradient in the triad

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6
Q

Higher PO2 near _______, lower PO2 near _________.

A

triad; central vein

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7
Q

Lipids contained in chylomicrons bypass the

A

hepatic portal circulation

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8
Q

Chylomicrons are secreted into

A

intestinal lymphatics

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9
Q

Between meals, splanchnic blood flow is

A

decreased

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10
Q

During digestion, splanchnic blood flow is

A

increased

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11
Q

What 4 elements contribute to postprandial hyperemia?

A
  • Anticipatory phase
  • Increased mucosal metabolic activity
  • Hyperosmolarity
  • Presence of vasoactive hormones
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12
Q

Exercising too soon after a meal and hemorrhage
can

A

reduce splanchnic blood flow

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13
Q

Due to the time frame for postprandial hyperemia, exercising too soon
following a meal will result in

A

underperformance of exercising skeletal muscle
groups.

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14
Q

Reduction in splanchnic blood flow is mediated by the

A

sympathetic division of
the ANS.

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15
Q

During exercise or hemorrhage, alpha,1-adrenergic receptor activation can

A

reduce
splanchnic blood flow to 25% of baseline values.

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16
Q

Pathologies from severe hemorrhage plus
prolonged splanchnic vasoconstriction can cause…

A
  • Villus tips to slough off
  • Pancreatic factors from cellular death appear in the general circulation
  • Volume expansion soon after severe hemorrhage will try to counter this set of events throu RAAS
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17
Q

If splanchnic vasoconstriction and hemorrhage is prolonged, then the
GI barrier will

A

Breakdown and tissue can undergo cell deah pathways

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18
Q

Small bowel secretions made are also known
collectively as the

A

Succus Entericus

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19
Q

All solutions secreted into the lumen of the SI are

A

isotonic

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20
Q

SI secretions are derived from what 3 sources?

A
  • Brunners gland
  • Duodenal bicarbonate secretion
  • Fluid secreted by the crypts
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21
Q

Fluids secreted by the crypts are

A

isotonic, neutral pH and enzyme rich

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22
Q

What is the primary method for neutralizing gastric acid from the stomach, protecting the duodenal mucosa and allowing pancreatic enzymes to function at a more neutral pH?

A

Duodenal bicarbonate secretion

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23
Q

Cholera toxin can increase ______ and promote the secretion of chloride ions into the intestinal lumen

A

cAMP

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24
Q

What is the important enzyme in converting pancreatic trypsinogen into trypsin?

A

Enterokinase

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25
Digestion of proteins begins in the stomach with what?
pepsin
26
Is pepsin essential for normal protein digestion?
No, but it begins it in the stomach
27
What are the 2 classes of peptidases?
- Endopeptidases - Exopeptidases
28
Examples of endopeptidases
Trypsin, pepsin, chymotrypsin, elastase
29
Examples of exopepdidases
carboxypeptidases
30
What are products of protein digestion?
Amino acids, dipeptides, and tripeptides
31
AAs are transported into the small intestinal cell by
sodium gradient
32
Dipeptides and tripeptides transported based on a
H+ driven symporter
33
In disorders of the exocrine pancreas, chronic pancreatitis and cystic fibrosis can lead to a
deficiency of proteases which can compromise protein absorption
34
What is cystinuria?
Rare genetic disorder where a dibasic AA transporter is nonfunctional in the GI and kidney
35
Digestion of starch starts in saliva with
alpha-amylase
36
Carbs must be digested in what forms to be absorbed by the small intestine?
Glucose, galactose or fructose
37
Glucose and galactose get absorbed by what transporter?
SGLT1 transporter
38
Fructose is absorbed by what?
GLUT5 in apical membrane
39
What is GLUT2 responsible for?
Bringing glucose, galactose or fructose into the portal circulation
40
What are the final lipid products?
Monoglycerides, fatty acids, lysolecithin and glycerol
41
Rate of gastric emptying is slowed by what?
CCK
42
What emulsifies lipids?
Bile salts and pancreatic enzymes
43
What does pancreatic lipase do?
Hydrolyzes TAGs
44
What is co-lipase activated by?
Trypsin and it displaced bile salts to help pancreatic lipase to perform function
45
What does cholesterol ester hydrolase do?
Converts cholesterol esters to free fatty acids and cholesterol
46
What does phospholipase A2 do?
Converts phospholipid to lysolecithin and fatty acids
47
What is phospholipase A2 activated by?
trypsin
48
Apolipoprotein B (ApoB) is necessary for the
exocytosis of chylomicrons into the lymphatics.
49
Deficiency in the MTTP gene results in
abetalipoproteinemia.
50
* Deficiency in the MTTP gene results in abetalipoproteinemia and can lead to
Fat malabsorption and the inability to absorb fat soluble vitamines
51
Reabsorption of water and electrolytes take place in
duodenum, jejunum, ileum and colon
52
Absorbed fluid is always
isosmotis
53
What is the major site for water, electrolyte and nutrient absorption?
Jejunum
54
Sodium can be absorbed via the following mechanisms:
* Na+ and nutrient (glucose) co-transport * Na+/H+ exchanger * Electroneutral NaCl transport * Electrogenic Na+ transport * Paracellular water transport (solute drag)
55
Water will follow absorbed _____ to maintain osmotic balance
Na+
56
Ileum is a reserve for
absorption of bile and vitamin B12. Can also absorb short chain fatty acids
57
What mediates the fasting state?
MMCs
58
What mediates the fed state?
Segmentation and peristalsis
59
Transit rates determines
how much of the poorly digested and or poorly absorbed food will actually be absorbed into the hepatic portal circulation
60
Increased fat in small bowl will do what to the transit rate?
Slow it
61
What are the 3 basic types of motor activity in the fed small bowel?
- Mixing (segmenting) contractions - Propulsive contractions (peristalsis) - Villus movements (extension and retraction)
62
Propulsive (peristalsis) movements require
an intact and functional ENS
63
Movement of villi occurs whent he SI is
filled with chyme
64
Villus movement is mediated by
contractions of the muscularis mucosa
65
Unstirred water layer results from what?
the capillary of cloesly spaced microvilli
66
Unstirred water layer will be a barrier to
absorption of all materials, especially fats
67
The thickness of unstirred water layer is inversely proportional to how
vigorously the contents are being mixed
68
Severing vagal efferent motor nerves of the small intestine will do what?
Reduce intensity of motor activity, but does not stop it
69
In the unstimulated or resting state, what has the overall inhibitory effect?
ENS
70
Short or local reflexes are stimulated by what?
Distension, segmentation and peristalsis
71
Systemic reflexes are termed the
Vago-vagal reflexes
72
Enterogastric reflex can occur from
stretch, presence of acid (fats), hypertonicity in SI that will stimulate several neural and hormonal components
73
Gastro-colic refelx is the
filling of the stomach that will icnrease distal motor activity in the colon to promote defecation
74
Entero-enteric reflex is
an increase in motor activity distal to a distending or irritating stimulus while decreasing proximal motor activity
75
Colonocytes will absorb fluid and electrolytes, but
do not express digestive enzymes
76
Segmentation rate increases as it
reaches colon to allow for the reabsorption of fluid
77
What is the stimulus for defecation?
Increased intrarectal pressures from increased volume
78
Defecation pathway is through a pelvo-pelvic nerve via stimulation of what?
Adenosine
79
Defecation involves what 2 integrated and simultansous events?
- Stimulation of defecation reflex - Changin the anorectal angle
80
External anal sphincter is under what control?
Voluntary
81
External anal sphincter is mainly skeletal muscle via the
pudendal nerve
82
In the distal colon, Cl will be reabsorved due to what?
Negative lumen potential due to electrogenic Na/K pumps
83
In distal colon, Na+ absorption via ENaC occurs along with
K+ secretion
84
What can stimulate the transporters in the distal colon?
Aldosterone
85
Secretory diarrhea (cholera toxin) will result in
volume contraction and a decrease in arterial pressure

Systems 1 (34 decks)

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