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144 Cards in this Set
- Front
- Back
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esophagus funcs:
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- transports food from the mouth to the stomach
-prevents retrograde flow of gastric contents |
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how does esophagus transport food?
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peristaltic contractions and relaxation of esophageal sphincters (upper and lower)
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what controls the esophageal sphincters?
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reflexes
autonomic nervous system |
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what type of epithelium covers the esophagus?
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nonkeratinized stratified squamous epithelium
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where are the esophageal glands? what are they?
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mucosa
small mucus-secreting glands |
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what is the function of esophageal glands?
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helps foodstuff transport
protects mucosa |
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where are the esophageal cardiac glands? do what?
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in lamina propria of region near stomach
secret mucus |
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what type of muscle is at the distal end of the esophagus?
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smooth muscle cells
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what type of muscle cells form the lower esophageal sphincter?
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smooth muscle cells
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what is the only part of esophagus that's covered by serosa?
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part that's in peritoneal cavity
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some of esophagus is covered by serosa.. what's the rest of esophagus covered by?
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layer of conn tissue: adventitia
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what has gone wrong in gastroesophageal reflux disease?
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incompetent barriers @ gastroesophageal junc caused by a decrease in the lower esophageal sphincter tone or hiatus hernia
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when does reflux esophagitis develop?
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when mucosal defenses aren't enough to protect esophageal mucosa from acid, pepsin, and bile --> heartburn or atypical chest pain
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what items can cause gastric reflux by relaxing lower esophageal sphincter?
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excessive gastric distension
fatty meals smoking tea coffee things w/ high xanthine content |
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what are the 4 parts of the stomach?
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cardia
fundus body pylorus |
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which parts of stomach are identical histologically?
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fundus
body |
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how are the mucosa and submucosa aligned in the undistended stomach?
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lie in longitudinally directed folds aka rugae
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what happens to rugae when the stomach is full of food?
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flatten out
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what does the gastric mucosa consists of?
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surface epithelium that invaginates into the lamina propria, making gastric pits
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what empties into the gastric pits?
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branched, tubular glands
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what is the lamina propria of the stomach made of?
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loose conn tissue interspersed w/ smooth muscle and lymphoid cells
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what separates the mucosa from the underlying submucosa in the stomach?
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muscularis mucosae: smooth muscle
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what type of epithelium covers the surface and lines the pits in the stomach?
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simple columnar epithelium
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what do all the cells of the stomach epithelium secrete?
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alkaline mucus made of water lipid and glycoproteins which form a hydrophobic protective gel
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what compound is secreted by the surface epithelial stomach cells into the mucus gel? what does it do?
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bicarbonate, forming pH gradient from 1 at the gastric luminal surface to 7 along epithelial cell surface
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which layer of mucus is effective in protecting the stomach cells? which isn't?
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is- layer adherent to epithelial surface
isn't- superficial luminal mucous layer b/c it's more soluble and is partially digested by pepsin and mixed w/ luminal contents |
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how are surface epithelial cells in the stomach a good line of defense?
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-make mucus
-intracellular tight juncs -ionic transporters that keep intracellular pH -bicarbonate prod -rich submucosal circulatory bed |
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what is the purpose of the rich submucosal circulatory bed in the stomach?
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-provides bicarbonate, micronutrients, and oxygen to mucosal cells
-removes toxic metabolic prods -favors healing of superficial wounds : mucosal restitution |
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what are some endogenous aggressors to the epithelial lining?
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HCl
pepsin lipases (lingual and gastric) bile |
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what can disrupt stomach epithelial layer and cause ulcers?
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stress
aspirin NSAIDS ethanol hyperosmolarity of meals Helicobacter pylori |
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what is an ulcer?
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a disruption of the mucosal integrity that leads to excavation due to active inflammation
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why do antiinflamm drugs result in ulcers?
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inhibit prod of prostaglandins
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what are cardia characteristics?
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narrow circular band
1.5-3 cm in width at transition b/w esophagus and stomach |
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describe cardia mucosa contents:
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has simple or branched tubular cardiac glands
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describe terminal parts of glands in cardia:
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frequently coiled
often w/ large lumens |
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what do most of the secretory cells in the cardia produce?
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mucus
lysozyme |
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what do parietal cells secrete?
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H+ and Cl-
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are there parietal cells in cardia?
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yes
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compare cardia glands to cardiac glands of the terminal part of the esophagus:
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similar in struc
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what is the lamina propria of the fundus and body filled with?
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branched, tubular gastric (fundic) glands
3-7 of which open into bottom of ea gastric pit |
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what are the parts of ea. gastric gland?
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isthmus
neck base |
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is the distribution of epithelial cells in gastric glands uniform?
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no
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what type of cells are in the isthmus?
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-differentiating mucous cells that will migrate and replace superficial mucous cells
-undifferentiated stem cells -oxyntic (parietal) cells |
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where is the isthmus in relation to the gastric pit?
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close to it
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what type of cells are in the neck of the gastric gland?
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stem cells
mucous neck cells (not like isthmus mucous cells) parietal cells enteroendocrine cells |
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what cells are in the base of the gastric gland?
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parietal
chief (zymogenic) cells enteroendocrine cells |
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describe struc of stem cells:
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low columnar cells w/ oval nuclei near bases of cells
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what is the mitosis rate of stem cells?
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high
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what is purpose of stem cells?
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move upward to replace pit and surface mucous cells OR
move down into glands and differentiate into mucous neck cels, parietal, chief, enteroendocrine cells |
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what is the turnover rate of surface mucous cells compared to neck and base cells?
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surface- turnover every 4-7 days
neck/base-much slower than surface |
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how are mucous neck cells arranged in tissue of fundus/body?
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in clusters or single cells b/w parietal cells
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is mucus secretion similar to surface epithelial mucous cells of fundus/body?
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no
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where is the nucleus in mucous neck cells of fundus/body?
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at the base
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where are the secretory granule in the mucous neck cells of fundus/body?
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near apical surface
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where are parietal cells usually located in fundus and body?
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upper half of gastric glands.. scarce at base
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what is the shape of parietal cells?
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pyramidal .. boobs
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describe nucleus and cytoplasm of parietal cells.
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nucleus- one centrally located
eosinophilic cytoplasm b/c lots of mitochondria deep, circular invagination of apical plasma membrane, forming intracellular canaliculus |
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what can be seen in the resting parietal cell in the apical region just below the plasmalemma?
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lots of tubulovesicular strucs
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what do tubulovesicles in parietal cells do when stimulated to make H+ and Cl-?
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tubulovesicles fuse w/ cell membrane to make canaliculus and more microvilli --> big increase in cell membrane surface
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what do parietal cells secrete?
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hydrochloric acid (H+ and Cl-)
KCl other electrolytes gastric intrinsic factor |
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how does parietal cell get H+ ion?
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from H2CO3 dissociation made by carbonic anhydrase- there's a lot of this enzyme in parietal cells
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why are there so many mitochondria in parietal cells?
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to keep up w/ high metabolic processes: especially the pumping of H+/K+
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what happens in atrophic gastritis?
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-much fewer parietal and chief cells
-gastric juice w/ little to none acid or pepsin activity -since fewer parietal cells, less intrinsic factor to bind vitamin B12 |
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list a couple ways to get pernicious anemia.
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atrophic gastritis
autoimmune disease against parietal cells |
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what initiates the secretory activity of parietal cells?
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cholinergic nerve endings (para stim)
histamine gastrin |
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where are histamine and gastrin both secreted into?
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gastric mucosa
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what do histamine and gastrin both stimulate?
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prod of HCl
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what effect does gastrin have on gastric mucosa?
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trophic effect: stimulates growth
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where are chief cells predominant in the fundus/body?
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lower region of tubular glands
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what type of cytoplasm do chief cells have: eosinophilic or basophilic? why?
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basophilic b/c lots of rough ER
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what are in the chief cell granules?
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pepsinogen
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when does pepsinogen become pepsin?
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after being released into acid env of stomach
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how many diff pepsins are in the human gastric juice?
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7
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describe the pepsins in human gastric juice:
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aspartate endoproteinases
broad specificity active @ pH <5 |
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what enzymes do chief cells produce?
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pepsinogen
lipase |
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where are enteroendocrine cells found in the fundus/body?
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neck and bases of gastric glands
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what is one of the principal secretory products of enteroendocrine cells in the stomach fundus?
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5-hydroxytryptamine
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what are carcinoids?
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tumors that arise for enteroendocrine cells b/c of an overproduction of serotonin
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what is the effect of serotonin on the gut?
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increases gut motility
-high levels relate to mucosal vasoconstriction and damage |
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describe the pylorus tissue.
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deep gastric pits in which branched, tubular pyloric glands open
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how do pyloric glands compare to cardiac glands?
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pyloric glands have longer pits and shorter coiled secretory parts
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what do pyloric glands secrete?
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mucus
lysozyme |
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what are gastrin (G) cells in pylorus?
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enteroendocrine cells intercalated among mucous cells of pyloric glands
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what stimulates the G cells to release gastrin in the pylorus?
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-parasympathetic stimulation
-presence of nutrients like aa and amines -stomach distension |
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what does G cell secretion activate?
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parietal cell --> increases acid secretion
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what inhibits gastrin in the pylorus?
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D cells- enteroendocrine cells that secrete somatostatin
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what's the submucosa of the stomach made of?
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conn tisse that has blood and lymph vessels
-infiltrated by lymphoid cells, macrophages and mast cells |
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what the muscularis of the stomach made of?
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smooth muscle fibers oriented in 3 directions
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what are the 3 directions of the muscle fibers in the muscularis?
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external -longitudinal
middle- circular internal - oblique |
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what is the middle layer of the muscularis like in the pylorus?
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greatly thickened to form pyloric sphincter
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what's the stomach covered by?
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thin serosa
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what are the folds inside the small intestine called? consist of?
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plicae circulares (Kerckring's valves)..
consist of mucosa and submucosa -have semilunar, circular, spiral form |
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where are plicae the most developed in?
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jejunum
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how long are intestinal villi?
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.5-1.5 mm long outgrowths of the mucosa projecting into SI
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what is the shape of intestinal villi in the duodenum?
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leaf shaped
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what is the shape of intestinal villi in the ileum?
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fingerlike
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what are between the villi?
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small openings of simple tubular glands (intestinal glands/ glands of Lieberkuhn)
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what kind of cells do intestinal glands have in SI?
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stem cells
absorptive cells goblet cells Paneth's cells enteroendocrine cells |
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what type of cells are enterocytes/absorptive cells? nucleus location?
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tall columnar cells
-oval nucleus in basal part of cell |
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what is at the apex of enterocytes?
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homogeneous layer: striated/brush border - densely packed microvilli
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about how big is a microvillus on an enterocyte?
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1 micrometer tall by .1 micrometer in diameter
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how many microvilli does each absorptive cell have?
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3000 microvilli
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how many microvilli does 1mmsquare have?
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200 million microvilli
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what increases the surface area of intestinal lining?
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plicae
villi microvilli |
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how much do plicae, villi, and microvilli increase surface by?
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plicae: 3x
villi: 10x microvilli: 20x in total: 600x.. total area of 200 msquare |
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what enzymes are part of the brush border? how attached?
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disaccharidases and peptidases
-bound to microvilli in brush border |
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where does most of lipid absorption happen?
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duodenum
upper jejunum |
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what is clinical picture in person deficient in disaccharidases?
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malabsorption
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where are goblet cells in the SI?
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interspersed b/w the absorptive cells
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many goblet cells in the duodenum? ileum?
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duodenum- less abundant
approaching ileum- inc in number |
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what do goblet cells make?
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-acid glycoprotein of mucin type
-these glycoproteins are hydrated and cross-linked to make mucus |
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what is the main func of mucus?
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protect and lubricate intestine lining
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where are Paneth's cells?
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basal part of intestinal glands
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what type of cells are Paneth's cells?
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exocrine cells w/ large eosinophilic secretory granules in apical cytoplasm
-lysozyme activity may control intestial flora |
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M (multifold cells) are what types of cells?
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epithelial cells
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where are M cells?
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overlying lymphoid follicles of Peyer's patches
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what characterizes the presence of M cells in tissue?
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lots of basal membrane invaginations that make pits that have lots of intraepithelial lymphocytes and antigen presenting cells (macrophages)
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what can M cells do to antigens?
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endocytose them
then, transport them to underlying macrophages and lymphoid cells, which then migrate to other lymphoid system compartments where immune responses to foreign antigens are initiated |
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describe the basement membrane under M cells
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discontinuous, facilitating transit b/w lamina propria and M cells
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what makes up the GALT: gut associated lymphoid tissue? where is it?
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in mucosa and submucosa:
antibody-secreting plasma cells macrophages lots of lymphocytes |
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what is the SI lamina propria made of?
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loose conn tissue w/ blood and lymph vessels, nerve fibers and smooth muscle cells
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describe duodenal (Brunner's) glands?
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clusters of ramified, coiled tubular glands that open into intestinal glands
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where are the duodenal (Brunner's) glands?
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submucosa
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what type of cells are Brunner's glands?
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mucous type
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what type of secretion comes from Brunner's glands?
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alkaline (pH 8.1-9.3)
-protect duodenal mucous membrane from acid gastric juice effects -bring intestinal contents to optimum pH for pancreatic enzyme action |
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what are the layers of muscularis in the intestines?
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internal circular layer
external longitudinal layer |
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where are the blood vessels in the intestine?
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penetrate muscularis and form large plexus in submucosa
from submucosa, branches extend thru muscularis mucosae and lamina propria and into villi |
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how does capillary network contribute to villus?
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each villus gets 1 or more branches that form capillary network just below epithelium
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how do venules contribute to villus?
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at tips of villi, one or more venules arise from capillaries and run in opp direction, reaching veins of submucosal plexus
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how do the lymph vessels contribute to villus?
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lymph vessels of intestine begin as closed tubes in villi core.. lacteals run to region of lamina propria above muscularis mucosae where they make a plexus,
then, go to submucosa, where they surround lymphoid nodules lacteals anastamose repeatedly and leave intestine |
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what forms innervation of intestines?
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intrinsic component
extrinsic component |
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what does the intrinsic component make up?
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myenteric / Auerbach's nerve plexus
submucosal/ Meissner's nerve plexus |
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where are the myenteric/Auerbach's nerve plexus?
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b/w outer longitudinal and inner circular layers of muscularis
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where is the Meissner's plexus?
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submucosa
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what's the purpose of nerve plexi in intestines?
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have sensory neurons that get info from nerve endings near epithelial layer and in smooth muscle layer about intestinal content composition (chemoreceptors) and degree of intestinal wall expansion (mechanoreceptors)
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what is responsible for intestinal contractions that happen in total absence of extrinsic innervation?
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intrinsic innervation
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what nerve fibers form extrinsic innervation?
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parasympathetic cholinergic nerve fibers that stim the activity of intestinal smooth muscle AND by sympathetic adrenergic nerve fibers that depress intestinal smooth muscle activity
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are there villi in large intestine?
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no
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does LI have any folds?
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no.. only in distal/rectal part are there folds
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describe the intestinal glands in the LI?
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long and have lots of goblet and absorptive cells
small number of enteroendocrine cells |
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describe the absorptive cells of the LI.
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columnar
short, irregular microvilli |
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what are main funcs of LI?
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water absorption
fecal mass formation mucus production |
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why does LI have mucus?
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lubricates intestinal surface
covers bacteria and particulate material |
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how does muscularis form taeniae coli?
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3 thick longitudinal bands
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