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140 Cards in this Set
- Front
- Back
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Rugae
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distensible folds - interior of stomach
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Main function of stomach epithelium
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digest the food; not digest itself
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Where do glands open into stomach?
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at base of pits formed by epithelium
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surface of gastric epithelium
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surface mucous cell
tall columnar cells basal nuclei clear cytoplasm mucinogen granules apical surface has prominent glycocalyx |
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2 cell types at neck of gastric epithelium
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neck cell - mucous secreting
stem cells - predominantly replace surface cells shed into the chyme |
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3 layers of smooth muscle in gastric muscularis
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inner - oblique (primarily in cardiac region)
middle - circular (pyloric sphincter) outer - longitudinal (v. little in pyloric region) |
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In which region of the stomach are oxyntic glands found?
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fundus
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In body and fundus of the stomach, the glands are ____ relative to the pits
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DEEP
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cells found in the epithelium of the pyloric region
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parietal cells (HCl secreting)
endocrine cells (gastrin, somatostatin) |
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3 types of gastric secretory cells
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parietal, oxyntic cells
peptic, chief or zymogenic cells endocrine cells |
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Source of stomach acid
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parietal cells
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acid secretion in parietal cells is dependent on which enzymes?
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apical H/K ATPase
basal Na/K ATPase |
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2 substances secreted by parietal cells
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intrinsic factor
HCl |
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histological characteristics of parietal cells
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large, round to pyramidal
uniformly eosinophilic cells intracellular canaliculi lined by microvilli |
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intrinsic factor is required for the absorption of which nutrient?
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vit B12
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3 substances that regulate parietal cell secretion
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gastrin
histamine acetylcholine |
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what do peptic cells secrete?
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lipase
pepsinogen |
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what do endocrine cells release into the stomach's lamina propria?
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basal secretory granules
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2 types of enteroendocrine cells
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closed type
open type |
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closed type enteroendocrine cells =
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no apical contact with the lumen of the gland
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open type enteroendocrine cells =
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some part of cell in contact with lumen
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5 specific categoreies of enteroendocrine cells
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ECL - entero-chromaffin-like cells
EC - entero-chromaffin cells D A G |
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ECL cells
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closed type
primary type in fundic glands found mostly at base of gland, close to chief cells |
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regulatory chain in which ECL cells are involved
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circulating gastrin binds basal membrane receptors on ECL cells
--> release histamine into lamina propria histamine helps regulate parietal cell activity |
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EC cells
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release serotonin, which increases smooth muscle contraction
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D cells
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release somatostatin
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A cells
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release glucagon
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G cells
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near antrum
secrete gastrin gastrin increases HCl secretion from parietal cells |
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mucus blanket
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mucus blunts abrasion by chyme & gastric enzymes
HCO3- from parietal cells enters lamina propria capillaries --> surface cells --> mucus more alkaline |
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fluid phase of mucus blanket
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includes acid and pepsin secretion from fundic glands
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Primary digestive functions of small intestine
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absorption of nutrients from chyme in stomach
neutralizing acidic contents |
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immunological functions of small intestine
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transporting Ig's into lumen
alerting immune tissue to presence of pathogens providing a barrier to most ingested pathogens |
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Plicae circulares
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crescent folds of mucosa and submucosa of small intestine
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Where are the plicae most prominent?
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jejunum
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function of plicae
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increase the surface area of the small intestine
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crypts of Lieberkuhn, aka:
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intestinal glands
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intestinal glands are found where?
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in between villi
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microvilli
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apical modifications of absorptive epithelium (enterocytes)
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3 structures that increase small intestine surface area
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plicae
villi microvilli |
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predominant cell type in small intestine
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tall columnar cells
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Function of junctional complex in surface absorptive cells or small intestine
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tight diffusion barrier to water, ions
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enzymes responsible for maintaining ion gradients in surface absorptive cells
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Na+/K+ ATPases in basolateral mb
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chylomicrons exit the surface absorptive cells through ____ and then...
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basolateral membrane - enters intercellular cleft --> enter lymph capillaries (lacteals)
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What happens in the intercellular cleft during active absorption
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it enlarges
small water soluble molecules diffuse from cleft into lamina propria capillaries larger, insoluble chylomicrons enter the lacteals |
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secretory vesicles in the surface absorptive cells contain what?
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glycoproteins to be inserted into the glycocalyx
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Immune pathway in enterocytes
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M cells present Ag --> activates B cells
B cells differentiate --> plasma cells --> IgA |
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function of IgA bound to the apical membrane of enterocytes
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reduce binding and therefore entry of some pathogens
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Goblet cells - function
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produce mucinogen
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histological characteristics of paneth cells
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basophilic basal cytoplasm
v. acidophilic, large, apical secretory granules containing antibacterial lysozymes |
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APCs of MALT =
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M cells
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where are stem cells for the small intestine found?
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lower half of crypt
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how many cells does the small intestine shed per day
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10^8
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Effect of activation of mast cells in small intestine lamina propria
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increases Cl- secretion by intestinal epithelium
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What do myofibroblasts secrete?
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prostaglandins
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lamina propria cores of villia are specialized for...
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transport of absorbed material
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path of lymph leaving small intestine
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lymphatic capillaries --> superior mesenteric nodes --> intestinal trunk --> thoracic duct
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function of lacteals
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transport of larger, non water soluble molecules, especially chylomicrons
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core of plicae
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submucosa
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In what section of the small intestine are there glands and which glands are they?
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Brunner's glands in the duodenum
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Brunner's glands
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branched, tuboalveolar glands
zymogen and mucus secreting cells |
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major site of absorption of digested food
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jejunum
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section of small intestine with the largest density of both plicae and villie
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jejunum
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function of large intestine
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converts liquid contents of small intestine into solid waste,
reabsorbing water and salts lubricates contents for excretion |
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inner surface of colon
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SMOOTH:
no plicae or villi crypts are deeper than in small intestine |
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Where are there more Goblet cells: large or small intestine?
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large
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In the large intestine, enteroendocrine cells produce what 6 things?
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somatostatin
serotonin substance P glicentin pancreatic peptide VIP |
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Why do colon CA have a slow rate of metastasis?
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tumors can grow w/in mucosa but have no access to lymphatic system
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Collagen table
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thick layer of collagen and proteoglycans just beneath basal lamina of large bowel epithelium
may regulate water flow |
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Hirschsprung's disease
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hypertrophic, preganglionic nerves in muscularis mucosa
indicate loss of enteric glanglia --> no neural control of lower colon |
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tenia coli are formed from which layer?
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muscularis externa
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Where is there adventitia on the outside of the colon?
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posterior aspect of ascending and descending colon
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epithelium of colorectal zone
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simple columnar epithelium with crypts, as in colon
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epithelium of anal transitional zone
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epithelium changes from simple columnar epithelium -->
stratified with superficial layers of cuboidal, columnar, polygonal or flat |
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squamous zone epithelium
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non-keratinzied stratified squamous
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2 functions of signaling pathways in GI tract
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allow region of GI tract to know what is happening in other regions
allow region to regulate the arrival of luminal contents |
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2 examples of autocrine signaling in GI tract
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TGF-a & TGF-b
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what GI hormone also has neuroncrine function?
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CCK
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smooth muscle contraction neurocrine agents (2)
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ACh
Substance P |
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smooth muscle relaxation agents (2)
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GRP,
ACh |
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neurocrine agents stimulating gastrin release
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GRP
ACh |
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neurocrine agent stimulating secretion
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VIP
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CCK:
secreted by... stimulus for secretion target organ pathway |
secreted by intestinal mucusal endocrine cells
stimulated by FAs in small intestine (>C12) targets pancreas, gallbladder, stomach Membrane-bound receptors --> cAMP or Ca2+ |
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Gastrin
secreted by... stimulus for secretion target organ pathway |
secreted in stomach
stimulated by peptides, aa, stomach distention increases gastric acid secretion, stimulates growth of mucosa membrane-bound receptor --> cAMP, Ca2+ |
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Secretin
secreted by... stimulus for secretion target organ pathway |
secreted in duodenum, jejunum
stimulated by duodenal acidity targets exocrine pancreas, gastric muscles and gastric parietal cells |
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GIP:
secreted by... stimulated by target organ pathway |
secreted in stomach
stimulated by glucose, fat in small intestine stimulates insulin release, decreases gastrin release |
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somatostatin:
secreted by... stimulus for secretion target organ pathway |
secreted in stomach
stimulated by gastric acid inhibits release of gastrin, gastric acid, pancreatic, gastric contraction/emptying |
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motilin:
secreted by... stimulus for secretion target organ pathway |
secreted in intestine
stimulated by no food in GI tract initiates MMC in proximal GI tract |
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VIP
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secreted in intestine
stimulated by no food in GI tract inhibits GI smooth mm contraction stimulates intestinal anion secretion vasodilator |
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Action effected by signal from enteric NS depends on what?
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neurotransmitter of the neuron innervating the target cells
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Action of ACh on esophageal muscle
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contraction of esophageal muscle
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NTs in neurons innervating the lower esophageal sphincter
action |
VIP & NO
relax sphincter during swallowing |
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CCK ____ the gallbladder via _____
CCK _____ the sphincter of oddi via _____ |
CCK CONTRACTS the gallbladder via ACh
CCK RELAXES the sphincter of oddie via VIP |
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skeletal muscle mechanism of contraction
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Ca2+ binds troponin/tropomyosin
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smooth muscle mechanism of contraction
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calmodulin activates MLCK
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3 muscle functions in GI tract
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segmentation - mixing
peristalisis - propulsion tonic contraction - separation |
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tonic contraction =
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physiological sphincter
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function of upper esophageal sphincter
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prevents air from entering digestive tract
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where does neural control for swallowing originate?
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medulla
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LES
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lower esophageal sphincter
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Increased LES tone can result in ____
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dysphagia, regurgitation
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Decreased LES tone can result in _____
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gastroesophageal reflux
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2 types of motility functions that occur in stomach
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receptive relaxation
antral systole (peristalsis) |
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BERs
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basic electrical rhythms
= specialized pacemaker cells: DICTATE WHEN CONTRACTIONS *CAN* OCCUR |
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Do BERs effect muscle contractions?
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NO
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frequency of oscillations dictated by BERs
stomach duodenum ileum |
stomach: 3 depolorizations/min
duodenum: 12 depol/min ileum: 9 depol/min |
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more APs = _____ contractions
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STRONGER
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when does a contraction occur in the GI tract
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when an AP occurs at the same time as a peak depolarization
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where are BERs located in the stomach?
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mid region of the greater curvature of the stomach
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antral systole refers to...
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mixing process in the distal region of the stomach
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Function of pylorus
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keeps stomach from being damaged by bile
or duodenum from being damaged by too much acid |
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retropulsion
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contraction in distal stomach
pushes food back to middle for more mixing |
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MMC
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migrating motor complex
characteristic GI motility pattern during fasting or interdigestive periods cyclic |
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functions of MMC (3)
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housekeeping
keep lumen free of bacteria gastric emptying of indigestible solids |
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3 major functions of colon
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absorption of water & electrolytes
storage of indigestible and unabsorbed materials motor activity in the colon |
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Haustra
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tonic contractions of circular muscle
appear and disappear at long intervals |
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mass movements of colon
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disappearance of haustra
strong contractions with rapid transmission of contents only occurs 3-4 times a day |
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H ions are secreted into stomach lumen by _____ _____ transport
with/against its concentration gradient |
primary active transport
against its concentration gradient |
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H ions secreted into stomach lumen are generated by
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carbonic anhydrase-catalyzed
water + CO2 --> HCO3- + H+ |
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H ions go out apical side
what goes out basolateral side at same time? |
HCO3- goes down its concentration gradient
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3 major stimulators of stomach acid secretion (and receptors)
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gastrin
histamine (H2 receptor) ACh (M3 receptor) |
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2 major inhibitors of stomach acid secretion
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NO
prostaglandins |
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purpose of pancreatic duct cells
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fluid and electrolyte transport
acid neutralization |
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pancreatic acinar enzymes - protealytic
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trypsin
elastase chymotrypsin carboxypeptidase |
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pancreatic acinar enzymes - amylotytic
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alpha-amylase
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pancreatic acinar enzymes - lipolytic
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lipase
colipase phospholipases |
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pancreatic acinar enzymes - nucleases
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RNases
DNases |
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What enzyme activates pancreatic acinar enzymes when they react the intestine?
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enterokinase
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Mechanism for HCO3- secretion by pancreatic duct cells
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reverse of mechanism for secretion for H+ by stomach cells
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Etiology of diarrhea
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cholera toxin
heat stable enterotoxin of E Coli VIP activate AC or GC --> cAMP or cGMP results in stimulation of Cl- secretion or results in inhibition of electroneutral NaCl absorptive mechanism |
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lactase deficiency results in...
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diarrhea (reduced colon absorption)
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brush border membrane disaccaridases (4)
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glucoamylase
sucrase isomaltase lactase |
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where and how does glucose enter cells?
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predominantly in villus region of duodenum and jejunum
along with 2Na+ |
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glucose leaves intestinal cell through the
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glut-2 transporter (passive facilitated transport)
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What maintains the sodium gradient in the small intestine?
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sodium/potassium pump
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Disaccharidase deficiency
etiology symptoms |
congenital
primary - loss in adulthood secondary - celiac sprue, radiation enteritis malabsorption of lactose due to lactase insufficieny --> bacterial fermentation & gas distention and undigested lactose draws water into lumen --> diarrhea |
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influences gastric acid secretion through paracrine mechanism
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histamine
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secretin increases...
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HCO3 secretion by the pancreas
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Do gallbladder epithelial cells have plications?
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yes
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Glut 5
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fructose transport
apical |
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The digestive gland characterized by the presence of mucous acini, and mucous acini with
serous demilunes, is the: |
sublingual gland
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