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GI Flashcards

1
Q

tongue: lining mucosa

A
  • nonkeratinized stratified squamous epithelium on areas needing mobility
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2
Q

tongue: masticatory mucosa

A
  • keratinized stratified squamous epithelium covering bones
  • lamina propria bound to periosteum
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3
Q

tongue: muscle innervation

A

hypoglossal nerve

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4
Q

tongue: sensory innervation

A

anterior 2/3: trigeminal nerve
posterior 1/3: glossopharyngeal nerve

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5
Q

filiform papillae: shape, epithelium, characteristics

A
  • shape: slender, conical
  • keratinized stratified squamous
  • no taste buds, most numerous
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6
Q

circumvallate papilla: shape, epithelium, characteristics

A
  • large
  • non-keratinized strat squamous
  • have taste buds, form row anterior to sulcus terminalis
  • encircled by deep cleft which Von Ebner’s glands secrete into
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7
Q

taste buds: taste receptor cells characteristics

A
  • bipolar neurons
  • respond to sweet, sour, bitter, salt, umami
  • tastant molecule binds receptor, releases NT to afferent terminal
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8
Q

fungiform papillae: shape, epithelium, characteristics

A
  • mushroom-shaped
  • non-keratinized strat squamous
  • have taste buds
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9
Q

tongue: taste innervation

A
  • anterior 2/3: facial nerve
  • posterior 1/3: glossopharyngeal
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10
Q

parotid gland: characteristics

A
  • serous alveoli only
  • well-formed capsule, lobulated
  • secretory granules rich in amylase, IgA, lysozymes, peroxidase
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11
Q

submandibular gland: characteristics

A
  • mixed, mostly serous cells
  • serous demilunes present
  • capsule, lobulated
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12
Q

sublingual gland: characteristics

A
  • mixed, mostly mucus cells
  • serous demilunes present
  • no capsule
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13
Q

pharynx: epithelium

A
  • areas subject to abrasion: non-keratinized stratified squamous
  • areas not subject to abrasion: ciliated pseudostratified
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14
Q

pharyngeal constrictors: muscle type

A

skeletal muscle

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15
Q

enteric nervous plexuses in GI tract: locations

A

submucosal plexus: in submucosa
myenteric plexus: between 2 layers of smooth muscle in muscularis externi

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16
Q

enteric nervous system: functions, characteristics

A
  • controls peristalsis, gut secretions, local blood flow, lymph tissue function
  • modulated by ANS, can function without
  • found at all levels of alimentary canal
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17
Q

lymphatic nodules: contents

A
  • TLRs identify antigens
  • M cells, enterocytes
  • lined by follicle-associated epithelium
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18
Q

esophagus: mucosa

A
  • non-keratinized strat squamous
  • loose CT lamina
  • mucus glands near junction w/ stomach*** (esophageal cardiac glands in lower 1/3 only)
  • thick muscularis mucosa
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19
Q

esophagus: distinct feature of posterior 1/3

A

cardiac glands in mucosa

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20
Q

esophagus: submucosa

A
  • dense fibroelastic CT w/ esophageal glands
  • serous and mucus cells present
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21
Q

esophagus: muscularis externi in each portion

A

upper 1/3: skeletal muscle
middle 1/3: skeletal and smooth muscle
lower 1/3: smooth muscle

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22
Q

portions of GI tract w/ glands in submucosa

A
  • esophagus: esophageal glands
  • duodenum: brunner’s glands
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23
Q

junction of stomach and esophagus: changes

A
  • abrupt change in mucosa: stratified squamous becomes simple columnar
  • abrupt change in glands: move from submucosa to mucosa
  • abrupt change in muscle: third layer of smooth muscle (inner oblique) added to muscularis externi
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24
Q

stomach: mucus and submucosa form

A

rugae

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25
Q

stomach: parietal cells structure and function

A
  • large, round, acidophilic, centrally to basally located nucleus
  • secrete gastric acid to denature proteins, intrinsic factor for vitamin B12 absorption
  • found in neck/upper segment of gastric gland
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26
Q

stomach: chief cells structure and function

A
  • smaller, basophilic, basal nucleus
  • secrete pepsinogen (pepsin precursor) to hydrolyze cells
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27
Q

stomach: stem cells function

A

divide to replace all gland cells and epithelium

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28
Q

stomach: DNES cell type and function

A
  • G cells in pylorus secrete gastrin
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29
Q

stomach: mucus cells

A

secrete mucus to trap bicarbonate, protect stomach from self-digestion

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30
Q

cardiac stomach: mucosa

A
  • cardiac simple coiled tubular glands w/ mucus cells
  • short pits, long glands
  • few DNES and parietal cells
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31
Q

fundic stomach: mucosa

A
  • simple branches tubular glands, contain majority of gastric juice
  • short pits, long glands
  • lots of parietal, chief, DNES, stem cells
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32
Q

pyloric stomach: mucosa

A
  • long pits, short simple branched glands
  • lots of mucus cells, G-cells, few parietal
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33
Q

stomach: muscularis externi

A

3 layers of smooth muscle
- inner oblique
- middle circular
- outer longitudinal

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34
Q

stomach: adventitia

A

surrounded by mesothelium

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35
Q

small intestine: factors increasing surface area for absorption

A
  • length: 12-25 feet
  • plicae circularis: permanent elevations in mucosa and submucosa
  • microvilli
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36
Q

small intestines: paneth cells

A
  • secrete antimicrobial proteins that are retained in mucus blanket
  • at the base of crypts
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37
Q

small intestine: DNES cells

A
  • S cells secrete secretin
  • I cells secrete CCK
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38
Q

small intestines: goblet cells

A

secrete mucus to form protective gel coat

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39
Q

small intestines: enterocytes

A

have microvilli to form brush border

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40
Q

small intestines: mucosa, noting differences between portions

A
  • simple columnar epithelium w/ microvilli, goblet cells*
    *goblet cells increase distal to stomach
  • muscularis mucosa
  • jejunum has long villi, ileum has shorter villi
  • intestinal crypts extend to muscularis mucosa
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41
Q

small intestines: submucosa, noting differences between portions

A
  • loose CT
  • duodenum has brunner’s glands: open into intestinal crypts and secrete mucus/bicarbonate to neutralize chyme
  • ileum has peyer’s patches
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42
Q

colon: mucosa

A
  • simple columnar w/ absorptive cells, increasing number of goblet cells
  • no villi or plicae circularis
  • intestinal glands and crypts
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43
Q

colon: muscularis externi

A
  • inner circular, outer longitudinal
  • teniae coli in longitudinal
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44
Q

pectinate line

A

marks abrupt transition to non-keratinized strat squamous

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45
Q

internal and external anal sphincters

A

internal: smooth muscle, formed by thickening of internal circular layer
external: skeletal muscle

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46
Q

liver: functions

A
  • destroys ages RBCs, removes bilirubin, forms clotting factors and albumin
  • stores carbs as glycogen, forms urea from AAs, produces bile salts
  • detoxification
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47
Q

liver: structure

A
  • surrounded by dense irregular CT capsule
  • central vein w/ portal triad (portal venule, hepatic arteriole, bile ductule)
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48
Q

liver: perisinusoidal space

A

between endothelial cells and hepatocytes, drains ECF to space of mall

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49
Q

liver: portal acinus

A

diamond areas between 2 central veins, 2 portal veins
- based on hepatocytes vascularized by 2 branches of hepatic artery

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50
Q

gallbladder: mucosa

A
  • tall simple columnar
  • lamina propria of loose CT
  • folds when not distended
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51
Q

gallbladder: muscularis externi

A
  • smooth muscle, not in layers
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52
Q

gallbladder: serosa/adventitia

A

serosa on free surface, adventitia on surface against liver

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53
Q

pancreas: location of tail

A

ends in hilum of spleen

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54
Q

pancreas: location of body

A

anterior to abdominal aorta

55
Q

pancreas: location of neck

A

anterior to portal vein

56
Q

pancreas: location of head

A

in concavity of 2 part of duodenum

57
Q

pancreas: exocrine secretions, secretory units

A
  • pancreatic enzymes, bicarbonate, water into duodenum
  • serous alveoli
  • pyramidal serous cells secrete zymogens
58
Q

congestive heart failure: effect on liver

A
  • increased central venous pressure, IVC can’t get blood back into heart
  • leads to hepatomegaly
59
Q

portal hypertension: effects

A
  • obstruction to blood flow increases hydrostatic pressure in portal vein
  • fluid accumulates in peritoneal cavity (ascites)
  • loss of fluid aggravated by reduced plasma oncotic pressure due to reduced plasma albumin
60
Q

GI smooth muscle contraction

A
  • no RMP
  • weak baseline tonic contractions, stronger phasic contractions occur when wave is @ threshold and tirggers AP
  • frequency is intrinsic to each portion
  • ACh raises spike potential, epinephrine lowers it
61
Q

GI smooth muscle: tonic contraction

A
  • isolation of two portions of GI tract
  • examples: sphincters
62
Q

GI smooth muscle: segmentation

A
  • alternate contraction/relaxation of adjacent sections allows for mixing, churning
  • enhances digestion and absorption
63
Q

GI smooth muscle: peristalsis

A
  • wave moves down gut, preceded by relaxation
  • propels GI content forwards
64
Q

control of GI: enteric nervous system

A
  • primary GI regulator
  • myenteric and submucosal plexuses receive signals from mechano and chemoreceptors that sense local parameters to elicit local responses
65
Q

control of GI: CNS autonomic

A
  • brain and spinal cord receive sensory input
  • parasympathetic promotes GI function by increasing motility, secretions, relaxing sphincters
  • sympathetic inhibits
66
Q

gastrin: source

A

G cells in gastric antrum and duodenum

67
Q

gastrin: stimuli

A

peptides, amino acids, gastric distension, vagus nerve, plasma Ca2+

68
Q

gastrin: effects

A

increases stomach acid secretion by parietal cells, increases mucosal growth

69
Q

CCK: source

A

I cells in duodenum, jejunum

70
Q

CCK: stimuli

A

amino acids, fatty acids

71
Q

CCK: effects

A
  • increases gallbladder contraction and pancreatic digestive enzyme secretion
  • relaxes sphincter of Oddi so pancreatic juice and bile can flow from ampulla
  • slows gastric emptying by relaxing smooth muscle, contracting pyloric sphincter
72
Q

motilin: source

A

Mo cells in duodenum and jejunum

73
Q

motilin: stimulus

A

fasting

74
Q

motilin: effects

A

migrating motor complex (stomach growling)

75
Q

ghrelin: source

A

stomach

76
Q

ghrelin: stimulus

A

fasting

77
Q

ghrelin: effects

A
  • increased food intake, growth hormone secretion
  • released before mealtime
78
Q

somatostatin: source

A

D cells in stomach and duodenum

79
Q

somatostatin: stimulus

A

H+, low luminal pH

80
Q

somatostatin: effects

A

negative feedback loop to reduce gastrin secretion from G cells

81
Q

secretin: source

A

S cells in small intestine

82
Q

secretin: stimulus

A

H+, fatty acids

83
Q

secretin: effects

A
  • stimulates HCO3- secretion in bile, pancreatic juice to neutralize acid
  • increases pH for pancreatic digestive enzyme activity
  • decreases gastrin secretion
84
Q

GIP: source

A

K cells in duodenum, jejunum

85
Q

GIP: stimuli

A

glucose, fat

86
Q

GIP: effects

A

synthesis, secretion of insulin

87
Q

GLP-1: source

A

L cells in ileum

88
Q

GLP-1: stimulus

A

glucose

89
Q

GLP-1: effects

A

synthesis, secretion of insulin

90
Q

orexigenic hormone

A

ghrelin

90
Q

anorexigenic hormones

A

CCK, leptin, insulin, GLP-1

91
Q

saliva: characteristics

A
  • hypotonic, alkaline
  • contains water, ions, proteins, glycoproteins
  • digestive enzymes a-amylase, lipase initiate carb and fat digestion
  • hydration, lubrication, host defense
92
Q

saliva: nervous stimulation

A

sympathetic: less amount of concentrated, doesn’t stimulate ductal cell
parasympathetic: profuse, watery

93
Q

deglutition: initiation

A

voluntary movement of bolus into pharyngeal area stretches pharynx
- afferent signals sent to medulla, efferent through cranial nerves, vagus nerve

94
Q

deglutition: results of stimulation

A

glottic closure, sphincter relaxation, peristalsis, inhibition of respiration

95
Q

lower esophageal sphincter: function

A
  • relaxes as result of deglutition reflex
  • tonically contracted, relaxes upon swallowing so food can enter stomach
96
Q

stomach: fundus and body function

A

can act as a reservoir by relaxing to accommodate large volume of food

97
Q

stomach: antrum function

A

mixing w/ gastric secretions, mechanical grinding into smaller particles

98
Q

gastric emptying: type of food

A

carb enters duodenum fastest, then protein, then fat
solid meal takes longer than liquid meal

99
Q

gastric glands: parietal cells secrete

A

HCl, intrinsic factor

100
Q

gastric glands: enterochromaffin-like cells secrete

A

histamine

101
Q

gastric glands: chief cells secrete

A

pepsinogens

102
Q

gastric barrier: comprised of

A
  • tight junctions in epithelium are relatively impermeable to acid
  • mucus gel layer ( mucus + water, phospholipids, electrolytes)
  • surface epithelial cells secrete watery, isotonic substance to neutralize acid
103
Q

H. pylori effect on gastric barrier

A
  • urease production
  • urea prevents mucus secretion
104
Q

pepsinogen: breakdown to pepsin

A
  • positive feedback: pepsin can cleave, activate pepsinogen via autoactivation
  • spontaneous breakdown: acidic environment needed. pH must be <3.5 to prevent inactivation of pepsin
105
Q

pepsin: stimulates

A
  • proteins digested into small peptides, AAs: stimulate HCl, gastrin, CCK
106
Q

acid secretion: cells, stimuli

A
  • parietal cells secrete HCl at low basal level
  • increases in response to ACh, gastrin, histamine
  • main stimulus is histamine
107
Q

acid secretion: ions

A
  • H+ generated from rxn catalyzed by carbonic anhydrase, secreted into lumen by H-K ATPase
  • HCO3- from same rxn transported across basolateral membrane via Cl/HCO3- exchanger, bringing Cl- into cell
  • result: isotonic, acidic secretion
108
Q

intrinsic factor: secretion, function

A

parietal cells secrete for B12 absorption

109
Q

intrinsic factor deficiency can cause

A

pernicious anemia

110
Q

cephalic phase: stimuli, what it stimulates

A
  • body is stimulated by sight, smell, taste, thought, sound, contact of food
  • leads to vagal stimulation
  • vagal stimulation leads to gastrin secretion, histamine, H+ secretion
111
Q

gastric phase: stimuli, what it stimulates

A
  • food in stomach stimulates gastric distention, protein digestion
  • stimulates vagus, H+ secretion
112
Q

intestinal phase: stimuli, what it stimulates

A
  • food in duodenum leads to protein digestion to AAs
  • AAs stimulate gastrin release, stimulating H+ release
113
Q

trypsinogen to trypsin

A

trypsin can cleave trypsinogen
enteropeptidase cleaves trypsinogen

114
Q

bicarbonate functions

A
  • enters lumen, neutralizes stomach acid
115
Q

carbonic anhydrase

A
  • converts CO2 and H2O into bicarbonate and proton
  • bicarbonate enters lumen to neutralize stomach acid
  • H+ enters blood
116
Q

pancreatic secretion: cephalic and gastric phase

A
  • receives signals via vagus nerve, ACh stimulates acinar cells to release pancreatic enzymes
117
Q

chyme entering duodenum: effects

A
  • stomach acid stimulates S cell release of secretin
  • secretin binds ductal cells, increases bicarbonate secretion
  • CCK from I cells stimulated by products of fat, protein digestion
  • CCK activates acinar enzyme secretion
118
Q

bile production

A
  • secreted by hepatocytes into bile canaliculi
  • cholangiocytes secrete more water and bicarbonate to make bile more alkaline
119
Q

control of bile secretion: determined by

A
  • main control is CCK
  • hepatic production: stimulated by vagus nerve or CCK
120
Q

bile flow: determined by

A

tone of gallbladder and sphincter of oddi
- between meals, CCK is low, sphincter of oddi is contracted and gallbladder is relaxed, bile enters gallbladder

121
Q

gallbladder concentrates bile by

A

pumping sodium out

122
Q

bile secretion during meal

A

CCK and vagus nerve stimulate release of bile by contracting gallbladder, releasing sphincter of oddi

123
Q

bile synthesis

A
  • from cholesterol in hepatocytes
  • primary bile acids converted to secondary by intestinal bacteria
  • bile acids conjugated to glycine or taurine to form bile salts: more soluble
124
Q

small intestine: digestion, absorption

A

only monosaccharides can be absorbed
- brush-border hydrolases break disaccharides into monosaccharides
- glucose and galactose need secondary active transport
- oligopeptides, AAs can be absorbed by enterocytes
- lipids digested in lumen, products are assembled into chylomicrons

124
Q

bile acid metabolism

A
  • bile salts are amphipathic: emulsify lipids to form micelle, increasing surface area for digestion
  • most bile is recycled in enterohepatic circulation
125
Q

small intestine: motility

A
  • peristalsis sweeps content from stomach to distal ileum
  • segmentation mixes chyme w/ digestive fluid, promotes contact w/ digestive epithelium
  • tonic contraction prolongs transit time for nutrient absorption
126
Q

small intestine: secretion

A

large amount of alkaline mucus to neutralize stomach acid

127
Q

colon: motility

A

segmentation (haustration) mixes content, haustra can disappear for mass peristalsis, moving content a long distance
- can be stimulated by stomach distention via gastrocolic reflex

128
Q

colon: absorption

A
  • most water reaching colon is absorbed by colonic epithelium, making content more solid
128
Q

colon: secretion

A
  • colonic crypts secrete bicarbonate, K+
  • goblet cells secrete mucus: create barrier, lubricate surface
128
Q

defecation process

A
  • rectum acts as a reservoir for feces
  • fecal content in rectum distends wall, initiating reflex
  • rectal wall contracts, internal sphincter relaxes, external sphincter contracts
  • voluntary desire relaxes sphincters, pelvic floor muscles. ab muscles contract
129
Q

colon: digeston

A
  • acts as reservoir
  • colonic bacteria produce SCFAs, B1, B2, B12, vitamin K

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