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Pathophys Exam I > GI Mod 3A > Flashcards

GI Mod 3A Flashcards

1
Q

3 regions of SI + lengths

A
  1. duodenum (25-30cm)
  2. jejunum (2.5m)
  3. ileum (3.5m)
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2
Q

where does the duodenum begin and end

A

begins - duodenal bulb

ends - ligament of Treitz

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3
Q

what is the hepatopancreatic ampula in SI

A

aka Sphincter of Oddi

-allow bile and pancreatic enzyme secretions

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4
Q

what are Brunner’s glands in SI

A

submucosal glands

  • located in proximal duodenum
  • secrete bicarbonate rich mucus to protect against acidic chyme entering the duodenum and lubricate intestinal wall
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5
Q

function of duodenum

A

digestion and gastric feedback

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6
Q

how does the duodenum perform enzymatic digestion/breakdown of food

A

stimulates release of digestive enzymes from pancreas and gall bladder

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7
Q

the SI provides feedback to do what?

A

regulate the rate of gastric emptying

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8
Q

how does the SI provide feedback for gastric emptying

A

acidic chyme (fats, partially digested protein, hyper/hypotonic fluids) entering duodenum stimulate:

  1. long loop reflexes
  2. short loop reflexes
  3. release hormone messengers
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9
Q

what are long loop reflexes of SI feedback

A

mechanoreceptors/chemoreceptors stimulate CNS to increase sympathetic and decrease parasympathetic to stomach

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10
Q

what are short loop reflexes of the SI

A

mechanoreceptors/chemoreceptors in duodenum stimulate enteric neurons in stomach to decrease stomach motility

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11
Q

the SI releases hormone messengers that do what for feedback

-what hormones are involved

A

inhibit stomach motility/acid production

-secretin, VIP, CCK released from duodenum play role in inhibiting gastric motility and secretion

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12
Q

hormones of the duodenum: secretin function

A

regulate pH in duodenum, inhibitory to gastric activity and facilitates digestion

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13
Q

hormones of the duodenum: secretin stimulus

A

acidic (pH

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14
Q

hormones of the duodenum:secretin target organ/action

A

stomach - inhibits gastric secretions (inhibits gastrin) and inhibits motility
pancreas- stimulate pancreas to secrete watery bicarb solution
liver - stimulates bile output (promote fat digestion)
brunner’s glands of duodenum - stimulate secretion of alkaline rich mucus

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15
Q

hormones of the duodenum: CCK function

A

promotes bile/pancreatic enzyme release and inhibitory to gastric activity

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16
Q

hormones of the duodenum: stimulus of CCK

A

fatty chyme (fats, partially digested protein) entering duodenum

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17
Q

hormones of the duodenum: target tissue/action

A

stomach - inhibitory to gastric motility/secretions
pancreas - stimulate release of pancreatic enzymes
liver - stimulates bile output (promote fat digestion)
gallbladder - stimulates contraction to release stored bile

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18
Q

hormones of the duodenum: GIP function

A

gastric inhibitory peptide

-relative of secretin

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19
Q

hormones of the duodenum: stimulus of GIP

A

chyme entering duodenum

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20
Q

hormones of the duodenum: target tissue/action of GIP

A

stomach - inhibitory to gastric motility/secretions (some resources question this role and propose secretin is stimulus)
pancreas - stimulate insulin release

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21
Q

hormones of the duodenum: VIP

A

vasoactive intestinal peptide

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22
Q

hormones of the duodenum: VIP stimulus

A

chyme entering duodenum

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23
Q

hormones of the duodenum: VIP target tissue/action

A

stomach - inhibit gastric acid secretion

intestine - vasodilate BV, promote intestinal motility

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24
Q

hormones of the duodenum: intestinal gastrin role

A

similar role as gastrin released in the antrum of stomach

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25
Q

hormones of the duodenum: stimulus of intestinal gastrin

A

chyme entering duodenum

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26
Q

hormones of the duodenum: target tissue/action of intestinal gastrin

A

stomach - stimulate gastric motility and secretions

intestine - stimulate motility

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27
Q

hormones of the duodenum: motilin role

A

housekeeper of intestinal tract

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28
Q

hormones of the duodenum: stimulus of motilin

A

fasting or periodic release (every few hours)

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29
Q

hormones of the duodenum: target tissue/action of motilin

A

intestine - initiates MMC (migrating motor complex)

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30
Q

list all the hormones of the duodenum

A
  1. secretin
  2. CCK
  3. GIP
  4. VIP
  5. intestinal gastrin
  6. motilin
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31
Q

how long is the SI

A

5-6m

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32
Q

where does the jejunum begin and the ileum end?

A

begins at ligament of Treitz and ends at ileocecal valve

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33
Q

where does the SI begin and end

A

pylori sphincter and ends at ileocecal valve

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33
Q

general function of both the jejunum and ileum

A

continued digestion, absorption and secretion of brush borders enzymes to assist in digestion/absorption

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35
Q

function of jejunum

A

major site of digested fat, carb, protein, water, and electrolyte absorption

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36
Q

function of ileum

A

absorb vitB12, bile salts, and remaining digested nutrients and water not absorbed in jejunum

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37
Q

function of mucosal folds of jejunum and ileum

A

aka plica

physically slow the passage of food

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38
Q

function of villi in jejunum and ileum

A

cover mucosal folds

considered functional unit of SI: secretion and absorption

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39
Q

composition of villi in jejunum and ileum

A
  1. goblet cells - mucus secreting cells

2. absorptive columnar cells: site of absorption

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40
Q

what are microvilli in jejunum and ileum

  • location
  • function
A

located on end of each columnar cell
form the brush border of the mucosal surface
a thin layer of fluid is found along surface of brush border
function: facilitates absorption of all substances except water/electrolytes

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41
Q

what is the lamina propria layer of the jejunum and ileum

A

extends into each villi

contains lacteal and central arteriole

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42
Q

function of central arteriole in jejunum and ileum

A

capillary transport substances directly to liver via hepatic portal vein
(carbs, proteins, and some fats to directly to liver)

43
Q

function of lacteal in jejunum and ileum

A

transport fat molecules/substances (fats - mnoglycerides & fatty acids) to systemic circulation via thoracic duct

44
Q

what are the Crypts of Lieburkuhn in jejunum and ileum

-3 types of cells

A 
at the base of villi
3 types of cells: 
1. precursor cells
2. paneth cells
3. secretory cells
45
Q

function of precursor cells in Crypts of Lieburkuhn of jejunum and ileum

A

in SI epithelium (goblet cells and columnar cells)
turnover of intestinal epithelial cells
-migrate to tip of villi, mature SI epithelial cells slough off into intestine and serve as a source of endogenous protein
-complete turnover of SI is approx 4-7 days

46
Q

function of paneth cells in the Crypts of Lieburkuhn of jejunum and ileum

A

immune function - produce/secrete antibiotic peptides

47
Q

small intestine motility - avg transit time

A

average transit time in SI - 1-3 hrs (with large variations of 15 min to 5+hrs)

48
Q

stimulus of SI motility

A
  1. small intestine hormones: secretin, CCK, gastrin, motilin

2. intestinal reflexes

49
Q

three motility patterns occur in SI

A
  1. segmentation
  2. peristalsis
  3. migrating motor complex (MMC)
50
Q

what is segmentation

A

occurs during feeding
frequent small rhythmic contractions of circular muscle (8-12/min)
occurs more frequently than peristalsis
function: mixes chyme to allow contact with brush border

51
Q

what is peristalsis

A

occurs during feeding
coordinated waves of contraction/relaxation of longitudinal muscles (short segments - 10cm)
wave of contraction moves slowly ( 1-2cm/sec) to allow for digestion/absorption
function: moves chyme toward large intestine

52
Q

what is MMC

A

aka interdigestive myoelectric complex
occurs during FASTING
slow periodic waves of peristalsis that occurs every 1-2hrs
originate in stomach and pass thru small intestine
motilin plays a role in stimulus

53
Q

function of MMC

A

function: “house cleaning” - sweeps out stomach/SI
- -pushes along residual chyme, nondigested substances (fiber, bone)
- -bacteria homeostasis - transport bacteria to LI, prevent reflux of bacteria from LI

54
Q

what is the ileogastric reflex

  • stimulus
  • action
  • result
A

stimulus - ileum distended
action - inhibits gastric motility
result - slows dow adding more chyme to SI to allow terminal ileum to empty contents to LI

55
Q

what is the intestinointestinal reflex

A

inhibitory-protective reflex
stimulus - section of SI becomes distended
action - relaxes distal SI
result - allows chyme to be moved toward LI

56
Q

what is gastroileal reflex

  • stimulus
  • action
  • result
A

stimulus - increased stomach (gastric motility/secretion)
action - promotes terminal ileum motility/ileocecal valve relaxation
result - empty SI so it can receive more chyme from stomach

57
Q

ileocecal valve is regulated how and is it usually open or closed

A

regulated intrinsically

usually closed

58
Q

regulation of ileocecal valve opening

  • stimulus
  • action
A

valve opens similar to LES of esophagus and pyloric valve in stomach
stimulus - approaching peristaltic wave in the ileum
action - relaxation of the ileocecal sphincter

59
Q

regulation of ileocecal valve closing

  • stim
  • action
A

stimulus - distension of cecum/ascending LI

action - constriction of ileocecal valve

60
Q

function of secretory cells of Crypts of Lieburkuhn of jejunum and ileum

A

secrete brush border digestive enzymes

61
Q

total length of the large intestine

A

1.5 m

62
Q

where does the LI begin and end

A

begin - ileocecal valve

end - anus

63
Q

sections of the LI

A

cecum, appendix, colon, rectum,anus

64
Q

4 regions of the colon

A

ascending, transverse, descending, and sigmoid colon

65
Q

LI is an unique arrangement of what 2 types of muscle

A
  1. circular and longitudinal muscles is unique in LI
66
Q

what are teniae coli in the LI

A

3 longitudinal bands if muscle along length of colon

67
Q

what are haustra in the LI

A

pouches formed from circular muscle layer of intestine

68
Q

what is O’Bierne sphincter of LI

A

controls passage of chyme from sigmoid colon into rectum

69
Q

LI motility - 2 types

A
  1. segmental

2. peristalsis

70
Q

what are haustral segment contraction

A

occurs during fasting
individual haustra segments push contents (fecal mass) back and forth
function - maximize absorption of water and electrolytes in large intestine occurs a majority (90%) of the time

71
Q

what is multihaustral segmentation

A

occurs during fasting
several haustral segments contract and relax as a single unit
function - push contents (fecal mass) a short distance forward occurs less often (10% of time)

72
Q

what is mass movement peristalsis

A

promote emptying of the intestine into the sigmoid colon and rectum

73
Q

what are the 2 intestinal reflexes of the colon

A
  1. orthocolic reflex

2. gastrocolic reflex

74
Q

what is the orthocolic reflex of the colon

  • stim
  • action
A

stimulus - standing first thing in the morning stimulates peristalsis of LI
action - peristalsis propels fecal mass into sigmoid colon and rectum

75
Q

what is the gastrocolic reflex of the LI

A

stim - ingestion of food (occurs during or immediately after eating)
action - peristalsis propels fecal mass into sigmoid colon and rectum
–continuation of gastroileal reflex - increase motility of stomach promotes motility of SI

76
Q

what is the rectal reflex of a bowel movement
stim
action
inhibition

A

aka defecation
stim - stretch of rectum wall
action - relaxation of internal anal sphincter and the urge to have BM
inhibited - voluntary control; cerebral cortex input/motor pathways in spinal cord: contract the external anal sphincter

77
Q

clinical of rectal reflex - cauda equina syndrome

A

damage to nerve roots of lower spine

loss of bowel control

78
Q

digestion of carbs in the mouth

A

enzyme - salivary amylas

action - starches broken into smaller molecules (dextrin and oligosaccharides)

79
Q

digestion of carbs in SI

A
  1. pancreatic role
    enzyme - pancreatic amylase secreted from pancreas
    action - further breakdown starches into major oligosaccharides (lactose, maltose, sucrose)
  2. brush border
    enzyme - brush border enzymes (lactase,maltase,sucrase) secreted from secretory cells of base of villi (Crypts of Lieburkuhn)
    action - breakdown oligosaccharides (lactose, maltose, sucrose) into monosaccharides (galactose, glucose, and fructose)
80
Q

absorption of carbs

A

location - brush border of villi
action - monosaccharides (galactose, glucose, and fructose) are absorbed by villi capillaries and transport directly to liver via hepatic portal vein
NOTE: insulin not required for intestinal uptake of glucose

81
Q

digestion of proteins begins where?

A

stomach

82
Q

digestion of protein in stomach

A

enzyme: pepsin
NOTE: pepsinogen released from chief cells is converted into pepsin when combined with gastric acids (HCl)
action: break down protein into smaller protein molecules (proteoses, peptones)
NOTE: this site of protein digestion is not essential…SI is primary site

83
Q

digestion of protein in SI

A
  1. pancreatic role:
    enzyme: pancreatic enzymes (trypsin, chymotrypsin, carboxpeptidase) secreted by pancreas into duodenum
    action: breakdown protein molecules into smaller peptides (polypeptides and dipeptides)
  2. brush border role
    enzyme: brush border enzymes (aminopeptidases/dipeptidase) are secreted from secretory cells of base of villi (Crypts of Lieburkuhn)
    action: breakdown smaller peptides (polypeptides and dipeptides) into amino acids
84
Q

absorption of proteins

A

location - villi in SI

action - amino acids are absorbed by villia capillaries and transported directly to liver (via hepatic portal vein)

85
Q

digestion of fats requires what

A

emulsification

86
Q

emulsifying agents in GI

A

fatty acids, monoglycerides, lecithin, cholesterol, protein, bile salts

87
Q

what do emulsifying agents do

A

surround small fat articles and prevent them from reforming into larger fat droplets
emulsification reduces the surface tension and separates the molecules

88
Q

digestion of fats starts where

A

stomach

89
Q

digestion of fats in stomach

A

enzyme: gastric lipase
action: initiate breakdown of fats

90
Q

digestion of fat in SI

A
  1. emulsification of fat droplets
    action - smaller fat droplets are formed in the presence of emulsifying agents
  2. lypolysis
    enzymes: lipase, phospholipase, hydrolipase secreted from pancreas
    action - emulsified fat molecules are broken down into diglycerides, monoglycerides, FFAs, glycerol
91
Q

absorption of fats

A

fast molecule must be made water soluble to reach intestinal epithelium
–accomplished by formation of micelles (water soluble molecule)

92
Q

steps in fat absorption

A
  1. Micelles formation
  2. Transport of fats into columnar epithelial cell of SI
  3. transport of fats into lacteals
93
Q

what happens in Micelles formation

A

bile salts, fat molecules, cholesterol, fat soluble vitamins (A,D,E,K) combine to form a micelle

94
Q

what happens in the transport of fats into the columnar epithelial cell of SI

A
  • micelle can pass thru aqueous brush border fluid and contact epithelial cell
  • fat contents of micelle then diffuse into epithelial cell
  • left over bile salts from micelle remain in intestine and are reabsorbed in the distal ileum
95
Q

what happens during transport of fats into lacteals

A
  • inside the epithelial cells the fat molecules are resynthesized into triglycerides and phosphoplipids
  • these new fat particles are called chylomicrons
  • the chylomicrons exit the intestinal wall (epithelial cell) into lacteals of villi and are transported to heart and systemic circulation
  • NOTE: most fats are absorbed via lacteals however some fat(glycerol and fatty acids) are absorbed directly into capillary system
96
Q

chylomicrons exit the cell via what process in the transport of fats into lacteals

A

CHYLOMICRONS EXIT the cell via exocytosis

97
Q

fluid is ingested or secreted into GI tract thruout which regions of GI

A

all regions

98
Q

total ingested/secreted fluid into GI tract

A

7.5-8L/day

99
Q

which part of GI will absorb most fluid back into blood stream

A

SI - approx 85-90% reabsorbed in SI

100
Q

what will secrete and absorb the final fluid balance

A

LI - driven by electrolyte balance

–fine tunes fluid and electrolyte homeostasis

101
Q

how much fluid is excreted in stool in normal BM

A

100ml (1/10L)

102
Q

normal renal excretion of fluid

A

renal excretion = 1-2L/day

103
Q

vit b12 absorption

A

occurs in terminal ileum

absorption requries B12 to bind with IF - which is secreted by gastric parietal cells

104
Q

lack of B12 causes

A 
pernicious anemia (macrocytic anemia) - poor RBC formation
liver and kidneys store enough B12 to last for years

Pathophys Exam I (9 decks)

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