Small Intestinal Anatomy and Physiology Flashcards

1
Q

What are the 3 regions of the small intestine

A

Duodenum
Jejunum
Ileum

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2
Q

which region is the shortest and widest portion of the small intestine

A

duodenum

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3
Q

which region starts at the pyloric sphincter?

A

duodenum

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4
Q

which region is C-shaped and mostly retroperitoneal?

A

duodenum

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5
Q

which region is closely associated with the head of the pancreas?

A

duodenum

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6
Q

which region of the small intestine is the longest?

A

ileum (2 meters)

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7
Q

which region joins the large intestine at ileocecal sphincter?

A

ileum

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8
Q

the vast majority of the duodenum is ?

A

retroperitoneal

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9
Q

jejunum has what?

A

larger plicae circulares

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10
Q

the ileum has many ?

A

large lymphoid nodules (peyer’s patches)

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11
Q

the arterial supply for the first 2/3 of the duodenum comes from?

A

the hepatic artery of the celiac trunk
- Hepatic art. -> gastroduodenal art. -> superior pancreaticoduodenal art.

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12
Q

the arterial supply for the rest of the small intestine (last part of duodenum to ileum) comes from

A

the superior mesenteric artery

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13
Q

what receives venous blood from small intestine and portions of the large intestine, stomach, and pancreas

A

superior mesenteric vein

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14
Q

what are plica circulares?

A

folds of mucosa and submucosa, they are permanent ridges about 10 mm “tall”

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15
Q

what encourages mixing and cause chyme to spiral and slosh through the intestine

A

plica circulares

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16
Q

what are finger-like projections of mucosa that are 0.5-1 mm long and vastly increase the SA of epithelium

A

villi

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17
Q

what is too small to be seen individually and is called?

A

microvilli and brush border

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18
Q

what does L cells secrete?

A

Peptide YY

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19
Q

what does Peptide YY do?

A

inhibits gastric secretion and motility = slows gastric emptying

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20
Q

how is chyme propelled through the small intestine

A

peristaltic waves (peristalsis)

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21
Q

what is a peristaltic rush

A

a powerful wave of contractile activity that travels long distances down the small intestine

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22
Q

what causes a peristaltic rush

A

intense irritation or unusual distension

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23
Q

what is the “law of the gut”

A

distention in the alimentary canal causes distal parts of the canal to relax and proximal parts to contract

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24
Q

peristalsis is enhanced by?

A
  • gastrin
  • CCK
  • serotonin
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25
Q

peristalsis is inhibited by?

A
  • secretin
  • peptide YY
  • epinephrine
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26
Q

what are the requirements for gastric emptying into the small intestine (duodenum)

A
  • food particles must by very small
  • small volumes of low pH fluid
  • gradual release
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27
Q

what is the major organ that regulates the rate of gastric emptying

A

duodenum

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28
Q

what are some duodenal hormones?

A

CCK and Secretin

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29
Q

what substances release the most CCK

A

fats

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30
Q

what is the major paracrine regulator of gastric emptying

A

CCK
- increased CCK release = slowed gastric emptying

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31
Q

secretin also has a mild impact on ?

A

gastric emptying slowing it

32
Q

what is the major hormone that performs the role of the “ileal brake”

A

peptide YY

33
Q

If undigested foods are reaching the distal small intestine, then ? “slows everything down” – not just gastric motility, but motility of the proximal intestines as well

A

peptide YY

34
Q

when would the ileocecal valve forcefully close?

A

when excess pressure builds up in cecum

35
Q

where are Brunner’s glands found?

A

found proximal to the sphincter of Oddi

36
Q

what does brunner’s glands secrete

A

secrete alkaline mucous

37
Q

what is the function of brunner’s glands

A

protect duodenal wall from digestion by gastric juice

38
Q

what regulates the release of bile into the dudodenum fromt eh ampulla of vater

A

sphincter of Oddi

39
Q

if the sphincter of Oddi is closed, then bile is stored where?

A

gall bladder

40
Q

what are the protein digestion enzymes in the pancreas

A
  • trysin
  • chymotrypsin
  • elastase
  • carboxypeptidase
41
Q

what is the inactive form of trypsin

A

trypsinogen

42
Q

what is the activator for trypsinogen

A

enterokinase

43
Q

what is the inactive form of chymotrpsin

A

chymotrypsinogen

44
Q

what is the activator for chymotrypsinogen

A

trysin

45
Q

what does chymotrypsin do?

A

cleaves peptide bonds next to a wide range of amino acids

46
Q

what is the inactive form of elastase

A

proelastase

47
Q

what is the activator of proelastase

A

trypsin

48
Q

what does elastase do?

A

cleaves elastin

49
Q

what is the inactive form of carboxypeptidase

A

procarboxypeptidase

50
Q

what is the activator of procarboxypeptidase

A

trypsin

51
Q

what does carboxypeptidase do?

A

cleaves the carboxy-terminal ends of peptides

52
Q

what is the digestive enzyme for carbohydrate digestion in the pancreas

A

pancreatic amylase

53
Q

what are the lipid digestion enzymes in the pancreas

A

pancreatic lipase/co-lipase
phospholipase A2

54
Q

what is the activator of pancreatic lipase

A

co-lipase activates lipase at the micelle

55
Q

what does pancreatic lipase do?

A

cleaves triglycerides to fatty acids and 2 monoacyl glycerol

56
Q

what is the inactive form of phospholipase A2

A

prophospholipase

57
Q

what activates prophospholipase

A

trypsin

58
Q

what does phospholipase A2 do?

A

cleaves phospholipids

59
Q

what is the enzyme called in the mouth that digest carbohydrates? and what secretes it?

A

ptyalin (salivary amylase) and parotid gland

60
Q

what is the most important enzyme for digestion of starches

A

pancreatic amylase

61
Q

The brush border formed by the microvilli contain 3 major enzymes that digest the major disaccharide sugars in our diet

A
  • lactase
  • maltase
  • sucrase
62
Q

what are the two things in the stomach that helps with protein digestion

A
  • HCL
  • Pepsin
63
Q

what does HCL do to proteins in the stomach

A

denatures them which improves the “exposure” of peptide bonds to digestive enzymes

64
Q

what has the ability to digest collagen

A

pepsin

65
Q

33% of protein absorption as ?, 67% of protein absorption as ?

A

free amino acids and peptides

66
Q

what does bile contain that help the formation of micelles

A
  • lecithins
  • bile salts
  • cholesterol
67
Q

“outside” of the micelle is what? “inside of the micelle is ?

A

hydrophillic
hydrophobic with the dieatary lipids

68
Q

When absorption at the small intestine fails, nutrients remain in the lumen of the intestine. This can result in:

A
  • diarrhea
  • micronutrient deficiency
  • macronutrient deficiencies
69
Q

Types of malabsorption can be pathophysiologically organized into four major problems:

A
  • disturbances in intraluminal digestion
  • disturbances in terminal digestion
  • disturbances in transepithelial transport
  • disturbances in lymphatic transport
70
Q

celiac disease is what type of malabsorption

A

terminal and trans-epithelial

71
Q

explain basic celiac disease

A

Damage to the villi and microvilli results in loss of surface area and overall absorptive enterocyte function

72
Q

explain basic chronic pancreatitis

A

Lack of major digestive enzymes from the pancreas leads to major impairment of absorption, diarrhea, and nutrient deficiencies

73
Q

explain basic disaccharidase deficiencies (lactose intolerance)

A

Lack of disaccharide results in unabsorbed sugar in the lumen
->bacterial gas production and osmotic diarrhe

74
Q

explain gastroenteritis

A

Damage to the brush border or dysregulation of electrolyte transport results in impaired ability to absorb nutrients

75
Q

chronic pancreatitis is what type of malabsorption

A

intraluminal digestion

76
Q

disaccharidase deficiencies is what type of malabsorption

A

terminal digestion

77
Q

gastroenteritis is what type of malabsorption

A

terminal and trans-epithelial