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

GI Module 3A Flashcards

(94 cards)

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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
What stimulates release of intestinal gastrin?
Chyme entering duodenum
26
What is motilin and what does it do?
- Housekeeper of intestinal tract | - Initiates MMC (migration motor complex)
27
What stimulates motilin?
- Fasting | - Periodic release (q few hrs)
28
Where do the jejunum and ileum begin and end?
- Ligament of Treitz | - Ileocecal valve
29
Role of jejunum
Major site of digested fat, carb, protein, water, electrolyte absorption
30
Role of ileum
Absorbs Vit B12, bile salts, remaining digested nutrients and water not absorbed in jejunum
31
What are plica?
Mucosal folds in jejunum/ileum that physically slow passage of food
32
What are villi?
- Cover the mucosal folds of jejunum/ileum | - Considered function unit of SI (site of both secretion and absorption)
33
What are villi composed of?
- Goblet cells (mucus) | - Absorptive columnar cells w/microvilli on end of each
34
What do microvilli form?
- "Brush border" of mucosal surface | - Thin layer of fluid is found along surface
35
What is the function of the "brush border" layer of the mucosa in the jejunum/ileum and what forms it?
- Facilitates absorption of all substances except water/electrolytes (they go b/w cells) - Formed by microvilli
36
What is the lamina propria?
Layer that extends into each villi in jejunum/ileum to optimize absorption
37
What does the lamina propria contain?
Lacteal and central arteriole
38
Function and location of central arteriole?
- Transport substances directly to liver via hepatic portal vein - Located in lamina propria layer of jejunum/ileum
39
Function and location of lacteal?
- Transport fats to systemic circulation via thoracic duct | - Located in lamina propria layer of jejunum/ileum
40
What are Crypts of Lieberkuhn?
- At base of villi in jejunum/ileum | - Optimizes absorption
41
What are Crypts of Lieberkuhn composed of?
- Precursor cells of SI eipthelium (goblet, columnar) - Paneth cells (immune) - Secretory cells
42
Function of precursor cells in Crypts of Lieberkuhn
- 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
Complete turnover of SI epithelium occurs in approx:
4-7 days
44
Function of paneth cells in Crypts of Lieberkuhn
- Immune function | - Produce/secrete antibiotic peptides
45
Function of secretory cells in Crypts of Lieberkuhn
Secrete brush border digestive enzymes
46
Average transit time in the small intestine =
1-3 hours (large variations however)
47
Which hormones stimulate SI motility?
- Secretin - CCK - Intestinal gastrin
48
3 motility patterns that occur in SI:
1. Segmentation 2. Peristalsis 3. Migrating motor complex (MMC)
49
What is segmentation?
- Frequent small rhythmic contractions of circular muscle - 8 to 12 per min - More frequent than peristalsis
50
Function of segmentation
Mixes chyme to allow contact with brush border
51
Which is more frequent - segmentation or peristalsis?
Segmentation
52
Which motility patterns occur during feeding and which during fasting?
- Feeding: segmentation and peristalsis | - Fasting: MMC
53
What is peristalsis?
- Coordinated waves of contraction/relaxation of longitudinal muscles - Short segments of 10 cm and SLOW (1-2 cm/sec)
54
Function of peristalsis
Move chyme toward large intestine
55
What is migrating motor complex (MMC)?
- Slow periodic waves of peristalsis that occurs every 1-2 hours - Originates in stomach and passes through SI - Motilin helps stimulate this
56
Function of MMC
"House cleaning" - Sweeps out stomach/SI - Pushes along residual chyme, non-digested substances - Bacteria homeostasis
57
What are the intestinal motility reflexes?
- Ileogastric reflex - Intestinointestinal reflex - Gastroileal reflex
58
What stimulates the ileogastric reflex? What is its action?
- Ileum distension - Inhibits gastric motility - This adds more chyme to SI to allow terminal ileum to empty contents to LI
59
What stimulates the intestinointestinal reflex? What is its action?
- Section of SI distension - Relaxes distal SI - Allows chyme to be moved toward LI * Inhibitory protective reflex
60
What stimulates the gastroileal reflex? What is its action?
- Increased gastric motility/secretion - Promotes terminal ileum motility/ileocecal valve relaxation - Empties the SI so it can receive more chyme from stomach
61
Is the ileocecal valve normally open or closed?
Closed
62
How is opening of the ileocecal valve regulated?
Approaching peristaltic wave in ileum stimulates relaxation of sphincter *Opens similar to LES/pyloric valve
63
How is closing of the ileocecal valve regulated?
Distension of cecum/ascending LI stimulates constriction of sphincter
64
Where does the LI begin and end?
- Ileocecal valve | - Anus
65
What are the regions of the LI?
- Cecum - Appendix - Colon (also has regions) - Rectum - Anus
66
What are the regions of the colon?
Ascending, transverse, descending, sigmoid
67
What are teniae coli?
3 longitudinal bands of muscle along length of colon
68
What are haustra?
Pouches formed from circular muscle layer of LI
69
What is the O'Bierne sphincter?
Controls passage of chyme from sigmoid colon into rectum
70
What are haustra segment contractions and when do they occur?
-Individual haustra segments push contents back and forth -During fasting (occurs 90% of the time)
71
What are multihaustral segment contractions and when do they occur?
- Several segments contract and relax as a single unit - Push contents a short distance forward - During fasting (occurs 10% of the time)
72
What is the function of mass movement peristalsis?
Promotes emptying of the intestine into the sigmoid colon and rectum
73
What are the intestinal reflexes of the colon?
- Orthocolic - Gastrocolic - Rectal
74
What is the orthocolic reflex and what stimulates it?
- Peristalsis that propels fecal mass into sigmoid colon and rectum - Occurs upon awakening - Standing stimulates
75
What is the gastrocolic reflex and what stimulates it?
- "Continuation" of gastroileal reflex - Peristalsis propels fecal mass into sigmoid colon and rectum - Ingestion of food stimulates this
76
What is the rectal reflex and what stimulates it?
- Parasympathetic relaxation of internal anal sphincter and the urge to have BM - Stimulated by stretch of rectum wall
77
What is cauda equina syndrome?
- Damage to nerve roots of lower spine | - Results in loss of bowel control
78
Where does carb digestion begin?
Mouth
79
Which digestive enzymes work to break down carbs?
- Salivary amylase (mouth) - Pancreatic amylase - Brush border enzymes (lactase, maltase, sucrase)
80
How and where does carb absorption occur?
- 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
Where does protein digestion begin?
Stomach
82
Which enzymes work to break down proteins?
- Pepsin - Pancreatic enzymes (trypsin) - Brush border enzymes (peptidases)
83
How are proteins absorbed and where?
- Villi in small intestine | - Amino acids are absorbed and transported directly to liver
84
How are fats digested?
- Emulsification | - Small fat particles are surrounded by emulsifying agents and prevent them from re-forming into larger fat droplets
85
Where does digestion of fats begin and how does it proceed?
- Stomach by gastric lipase | - Then in the SI = emulsification and lypolysis
86
How are fats absorbed?
- Must be made water soluble | - This is accomplished by formation of micelles
87
What are micelles and what is their purpose?
- Water soluble molecules | - Makes fats water soluble in order to reach intestinal epithelium for absorption
88
What are the steps in fat absorption?
- 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
How do chylomicrons exit the intestinal epithelial cell?
Exocytosis
90
Total ingested/secreted fluid into GI tract per day =
7.5 to 8 L
91
What percentage of fluid in the small intestine is absorbed back into the blood stream?
Approx 85-90%
92
What is the LI's role in fluid management?
It "fine tunes" fluid and electrolyte homeostasis
93
In normal circumstances, how much fluid is excreted in stool?
100 mL (1/10 L)
94
Where does Vit B12 absorption take place and what does it require?
- Terminal ileum | - Requires binding with intrinsic factor

Pathophys II MHM - Exam 1 (9 decks)

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