| AREA | PROCESSES | SECRETIONS | CONTROLS | HISTOLOGY |
| Mouth | mechanical digestion
chemical digestion: starches->shorter chains deglutition |
saliva: salivary amylase (ptyalin), serous fluid, mucus, salts, lysozyme, | cephalic
physical contact (pressoreceptors) |
non-keratinized
stratified
squamous;
salivary glands |
| Esophagus | peristalsis begins | mucus | involuntary
reflex |
non-keratinized
stratified
squamous
esophageal glands skeletal & smooth muscle |
| Stomach | storage (up to 4 hrs)
mechanical digestion some absorption |
mucus | cephalic;
physical contact (pressoreceptors) gastric phase: gastrin intestinal phase: gastrin, GIP, enterogastric reflex |
simple columnar
epithelium with
goblet cells
gastric pits mucus neck cells enteroendocrine cells 3-layered smooth muscle |
|
chemical digestion: polypeptides ---> shorter chains |
pepsinogen + H+ =>
pepsin
pH = 1.5 to 3.5 |
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| gastrin* | ||||
| small intestine:
duodenum 10"
|
from pancreas: | CCK
from the duodenal enteroendocrine cells, stimulates pancreatic secretion,
release of bile from gallbladder, secretion of bile by liver, relaxation of
the Sphincter of Oddi; inhibits stomach.
|
simple columnar
epithelium
Brunner's glands in duodenum
goblet cells
plicae circularis
villi and microvilli | |
| polysacchharides -> shorter chains and maltose |
amylase |
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| polypeptides-> shorter chains & dipeptides |
trypsin, chymotrypsin, |
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| dipeptides->amino acids |
carboxypeptidase |
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| fats->glycerol & . fatty acids | lipase
|
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|
from intestine brush border: |
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| dipeptides -> amino acids |
amino- & carboxy- peptidases |
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|
disaccharides --> monosaccharides |
sucrase, maltase, lactase | |||
| from duodenal enteroendocrine cells into the bloodstream |
secretin cholecystokinin (CCK) |
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| neutralizes acid | bicarbonate from pancreas
pH = 8 |
secretin from duodenum | ||
| Emulsification of fats |
bile from gallbladder: |
CCK | ||
|
jejunum
ileum |
absorption of all digestive end products and 95% of water, takes place over 4 to 6 hours |
Peyer's patches in the ileum | ||
| colon | absorption over 12 hrs., mostly
water
haustral churning mass peristalsis |
mucus | gastroileal and
gastrocolic reflex |
epithelial clefts
goblet cells taenia coli |
| rectum | defecation | defecation reflex | skeletal muscle
rectal valves | |
| anus | internal and external sphincters | |||
*Note: substances in italics indicate hormones.