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Pathophys II MHM - Exam 1 > GI Module 3A > Flashcards

GI Module 3A Flashcards

1
Q

Total length of small intestine

A

5-6 meters

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2
Q

Where does SI begin and end?

A
  • Pyloric sphincter

- Ileocecal valve

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3
Q

Regions of the SI

A

Dudoenum, jejunum, ileum

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4
Q

Where does duodenum begin and end?

A
  • Duodenal bulb

- Ligament of Treitz

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5
Q

What is the function of the hepatopancreatic ampulla?

A

Allows bile and pancreatic enzyme secretions

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6
Q

What are Brunner’s glands and where are they located?

A

Submucosal glands

Located in proximal duodenum

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7
Q

What do Brunner’s glands do?

A

Secrete bicarb rich mucus to:

  • Protect against acidic chyme entering duodenum
  • Lubricate intestinal wall
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8
Q

Functions of duodenum

A
  • Enzymatic digestion

- Regulate rate of gastric emptying

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9
Q

What does acidic chyme entering the duodenum stimulate?

A
  • Long loop reflexes (duodenum to CNS)
  • Short loop reflexes (duodenum to stomach)
  • Both cause inhibition of gastric motility/secretion
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10
Q

Acidic chyme entering duodenum stimulates release of which hormones?

A
  • Secretin
  • VIP
  • CCK
  • Inhibit gastric motility/secretion
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11
Q

What are hormones of the duodenum?

A 
Secretin
CCK
GIP
VIP
Intestinal gastrin
Motilin
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12
Q

What is the function of secretin?

A
  • Regulates pH in duodenum
  • Inhibitory to gastric activity
  • Facilitates digestion
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13
Q

What stimulates secretin release?

A

Chyme entering duodenum

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14
Q

What are the target organs of secretin?

A
  • Stomach (inhibits gastrin)
  • Pancreas (to secrete watery bicarb)
  • Liver (stimulates bile output)
  • Brunner’s glands of duodenum (stimulates alkaline rich mucus)
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15
Q

What is the purpose of CCK?

A
  • Promotes bile/pancreatic enzyme release

- Inhibitory to gastric activity

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16
Q

What stimulates CCK?

A

Chyme entering duodenum

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17
Q

What are the target organs of CCK?

A
  • Stomach
  • Pancreas
  • Liver
  • Gallbladder (release of bile)
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18
Q

What is GIP?

A
  • Gastric inhibitory peptide

- “Relative” of secretin

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19
Q

What stimulates GIP release?

A

Chyme entering duodenum

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20
Q

What are the target organs of GIP?

A
  • Stomach

- Pancreas (to release insulin)

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21
Q

What is VIP?

A

Vasoactive intestinal peptide

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22
Q

What is VIP stimulated by?

A

Chyme entering duodenum

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23
Q

What are the target organs of VIP?

A
  • Stomach

- Intestine (vasodilation, promote motility)

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24
Q

What is the function of intestinal gastrin?

A

Similar to role of antrum gastrin (stimulates motility/secretions)

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25
Q

What stimulates release of intestinal gastrin?

A

Chyme entering duodenum

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26
Q

What is motilin and what does it do?

A
  • Housekeeper of intestinal tract

- Initiates MMC (migration motor complex)

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27
Q

What stimulates motilin?

A
  • Fasting

- Periodic release (q few hrs)

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28
Q

Where do the jejunum and ileum begin and end?

A
  • Ligament of Treitz

- Ileocecal valve

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29
Q

Role of jejunum

A

Major site of digested fat, carb, protein, water, electrolyte absorption

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30
Q

Role of ileum

A

Absorbs Vit B12, bile salts, remaining digested nutrients and water not absorbed in jejunum

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31
Q

What are plica?

A

Mucosal folds in jejunum/ileum that physically slow passage of food

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32
Q

What are villi?

A
  • Cover the mucosal folds of jejunum/ileum

- Considered function unit of SI (site of both secretion and absorption)

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33
Q

What are villi composed of?

A
  • Goblet cells (mucus)

- Absorptive columnar cells w/microvilli on end of each

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34
Q

What do microvilli form?

A
  • “Brush border” of mucosal surface

- Thin layer of fluid is found along surface

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35
Q

What is the function of the “brush border” layer of the mucosa in the jejunum/ileum and what forms it?

A
  • Facilitates absorption of all substances except water/electrolytes (they go b/w cells)
  • Formed by microvilli
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36
Q

What is the lamina propria?

A

Layer that extends into each villi in jejunum/ileum to optimize absorption

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37
Q

What does the lamina propria contain?

A

Lacteal and central arteriole

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38
Q

Function and location of central arteriole?

A
  • Transport substances directly to liver via hepatic portal vein
  • Located in lamina propria layer of jejunum/ileum
39
Q

Function and location of lacteal?

A
  • Transport fats to systemic circulation via thoracic duct

- Located in lamina propria layer of jejunum/ileum

40
Q

What are Crypts of Lieberkuhn?

A
  • At base of villi in jejunum/ileum

- Optimizes absorption

41
Q

What are Crypts of Lieberkuhn composed of?

A
  • Precursor cells of SI eipthelium (goblet, columnar)
  • Paneth cells (immune)
  • Secretory cells
42
Q

Function of precursor cells in Crypts of Lieberkuhn

A
  • Migrate to tip of villi
  • Mature SI epithelial cells slough off and serve as a source of protein
  • Complete turnover of SI is approx 4-7 days
43
Q

Complete turnover of SI epithelium occurs in approx:

A

4-7 days

44
Q

Function of paneth cells in Crypts of Lieberkuhn

A
  • Immune function

- Produce/secrete antibiotic peptides

45
Q

Function of secretory cells in Crypts of Lieberkuhn

A

Secrete brush border digestive enzymes

46
Q

Average transit time in the small intestine =

A

1-3 hours (large variations however)

47
Q

Which hormones stimulate SI motility?

A
  • Secretin
  • CCK
  • Intestinal gastrin
48
Q

3 motility patterns that occur in SI:

A
  1. Segmentation
  2. Peristalsis
  3. Migrating motor complex (MMC)
49
Q

What is segmentation?

A
  • Frequent small rhythmic contractions of circular muscle
  • 8 to 12 per min
  • More frequent than peristalsis
50
Q

Function of segmentation

A

Mixes chyme to allow contact with brush border

51
Q

Which is more frequent - segmentation or peristalsis?

A

Segmentation

52
Q

Which motility patterns occur during feeding and which during fasting?

A
  • Feeding: segmentation and peristalsis

- Fasting: MMC

53
Q

What is peristalsis?

A
  • Coordinated waves of contraction/relaxation of longitudinal muscles
  • Short segments of 10 cm and SLOW (1-2 cm/sec)
54
Q

Function of peristalsis

A

Move chyme toward large intestine

55
Q

What is migrating motor complex (MMC)?

A
  • Slow periodic waves of peristalsis that occurs every 1-2 hours
  • Originates in stomach and passes through SI
  • Motilin helps stimulate this
56
Q

Function of MMC

A

“House cleaning”

  • Sweeps out stomach/SI
  • Pushes along residual chyme, non-digested substances
  • Bacteria homeostasis
57
Q

What are the intestinal motility reflexes?

A
  • Ileogastric reflex
  • Intestinointestinal reflex
  • Gastroileal reflex
58
Q

What stimulates the ileogastric reflex? What is its action?

A
  • Ileum distension
  • Inhibits gastric motility
  • This adds more chyme to SI to allow terminal ileum to empty contents to LI
59
Q

What stimulates the intestinointestinal reflex? What is its action?

A
  • Section of SI distension
  • Relaxes distal SI
  • Allows chyme to be moved toward LI
  • Inhibitory protective reflex
60
Q

What stimulates the gastroileal reflex? What is its action?

A
  • Increased gastric motility/secretion
  • Promotes terminal ileum motility/ileocecal valve relaxation
  • Empties the SI so it can receive more chyme from stomach
61
Q

Is the ileocecal valve normally open or closed?

A

Closed

62
Q

How is opening of the ileocecal valve regulated?

A

Approaching peristaltic wave in ileum stimulates relaxation of sphincter
*Opens similar to LES/pyloric valve

63
Q

How is closing of the ileocecal valve regulated?

A

Distension of cecum/ascending LI stimulates constriction of sphincter

64
Q

Where does the LI begin and end?

A
  • Ileocecal valve

- Anus

65
Q

What are the regions of the LI?

A
  • Cecum
  • Appendix
  • Colon (also has regions)
  • Rectum
  • Anus
66
Q

What are the regions of the colon?

A

Ascending, transverse, descending, sigmoid

67
Q

What are teniae coli?

A

3 longitudinal bands of muscle along length of colon

68
Q

What are haustra?

A

Pouches formed from circular muscle layer of LI

69
Q

What is the O’Bierne sphincter?

A

Controls passage of chyme from sigmoid colon into rectum

70
Q

What are haustra segment contractions and when do they occur?

A

-Individual haustra segments push contents back and forth
-During fasting
(occurs 90% of the time)

71
Q

What are multihaustral segment contractions and when do they occur?

A
  • Several segments contract and relax as a single unit
  • Push contents a short distance forward
  • During fasting (occurs 10% of the time)
72
Q

What is the function of mass movement peristalsis?

A

Promotes emptying of the intestine into the sigmoid colon and rectum

73
Q

What are the intestinal reflexes of the colon?

A
  • Orthocolic
  • Gastrocolic
  • Rectal
74
Q

What is the orthocolic reflex and what stimulates it?

A
  • Peristalsis that propels fecal mass into sigmoid colon and rectum
  • Occurs upon awakening
  • Standing stimulates
75
Q

What is the gastrocolic reflex and what stimulates it?

A
  • “Continuation” of gastroileal reflex
  • Peristalsis propels fecal mass into sigmoid colon and rectum
  • Ingestion of food stimulates this
76
Q

What is the rectal reflex and what stimulates it?

A
  • Parasympathetic relaxation of internal anal sphincter and the urge to have BM
  • Stimulated by stretch of rectum wall
77
Q

What is cauda equina syndrome?

A
  • Damage to nerve roots of lower spine

- Results in loss of bowel control

78
Q

Where does carb digestion begin?

A

Mouth

79
Q

Which digestive enzymes work to break down carbs?

A
  • Salivary amylase (mouth)
  • Pancreatic amylase
  • Brush border enzymes (lactase, maltase, sucrase)
80
Q

How and where does carb absorption occur?

A
  • Brush border of villi
  • Monosaccharides are absorbed by villi capillaries and sent directly to liver
  • Insulin is NOT required for intestinal uptake of glucose
81
Q

Where does protein digestion begin?

A

Stomach

82
Q

Which enzymes work to break down proteins?

A
  • Pepsin
  • Pancreatic enzymes (trypsin)
  • Brush border enzymes (peptidases)
83
Q

How are proteins absorbed and where?

A
  • Villi in small intestine

- Amino acids are absorbed and transported directly to liver

84
Q

How are fats digested?

A
  • Emulsification

- Small fat particles are surrounded by emulsifying agents and prevent them from re-forming into larger fat droplets

85
Q

Where does digestion of fats begin and how does it proceed?

A
  • Stomach by gastric lipase

- Then in the SI = emulsification and lypolysis

86
Q

How are fats absorbed?

A
  • Must be made water soluble

- This is accomplished by formation of micelles

87
Q

What are micelles and what is their purpose?

A
  • Water soluble molecules

- Makes fats water soluble in order to reach intestinal epithelium for absorption

88
Q

What are the steps in fat absorption?

A
  • Micelles formed
  • Micelles pass through aqueous brush border and contact epithelial cell
  • Fat contents then diffuse into epithelial cell
  • Fats are resynthesized into TGs and phospholipids (aka chylomicrons)
  • Chylomicrons exit epithelial cell into lacteals of villi and are transported into systemic circulation
89
Q

How do chylomicrons exit the intestinal epithelial cell?

A

Exocytosis

90
Q

Total ingested/secreted fluid into GI tract per day =

A

7.5 to 8 L

91
Q

What percentage of fluid in the small intestine is absorbed back into the blood stream?

A

Approx 85-90%

92
Q

What is the LI’s role in fluid management?

A

It “fine tunes” fluid and electrolyte homeostasis

93
Q

In normal circumstances, how much fluid is excreted in stool?

A

100 mL (1/10 L)

94
Q

Where does Vit B12 absorption take place and what does it require?

A
  • Terminal ileum

- Requires binding with intrinsic factor

Pathophys II MHM - Exam 1 (9 decks)

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