GI 1

imissyou419's version from 2017-04-06 17:41


Question Answer
4 processes of GI tract1. digestion - chemical & mechanical,
2. absorption - small (majority) & large intestines only,
3. motility - helps with mechanical and mechanical digestion, absorption in small intestine by slowing motility, crushing ability of stomach,
4. secretion - exocrine secretions (water, mucus, enzymes to help with chemical digestion, motility or endocrine hormones, paracrine factors
Upper esophageal sphinctercloses off mouth to esophagus
Lower esophageal sphinctercloses off esophagus to stomach
Pyloric sphinctercloses off stomach to small intestine
Ileocecal valvecloses off small intestine to large intestine
Mucosa 3 layersMucous membrane (enterocytes - variable between stomach, intestine, large intestine),

Lamina propria - connective tissue that support mucous membrane, has lacteals and capillaries for absorption,

Mucularis mucosae - thin layer of smooth muscle, contract & relax causing stretching of mucosa (more folds - increase SA)
Submucosathicker lay of stretchy connective tissue with lacteals and blood vessels, adhere mucosa to mucularis externa
Muscularis externahas myenteric plexus, circular muscles & longitudinal muscles change shape of stomach to change motility and have crushing movements
Serosathin layer of connective tissue, continuous with mesentery to keep everything in place
Submucosal plexusin submucosa layer, receives information from inside of lumen (enterocytes) - distention, elicit neuronal response
Myenteric plexusMuscularis externa, innervate it so muscles can contract & relax for motility
SNS and PNS in relation to ENSENS receives input from CNS but it can function independent
(when PNS activated -> increase secretion (acid, mucous, enzymes) for digestion,
SNS activated -> slow digestion)
Function of the ENS1. control of motility,
2. regulation of local blood flow,
3. regulation of gastric (HCl) and pancreatic secretions,
4.regulation of endocrine cells of the GI tract,
5. Entero-enteric reflexes (neurons tell ileocecal valve to open for small intestines to empty into large intestines),
6. defense mechanisms (vomiting and diarrhea),
7. interactions with the CNS (if stomach full, brain should know so can stop eating)
Short reflexes of the ENSInternal (GI tract) stimuli -> chemoreceptors, osmoreceptors, mechanoreceptors detect composition of food -> local (intrinsic) nerve plexus - the 2 plexus -> Effectors: smooth muscles or glands, Response: change in contractile or secretory activity
Long reflexes of the ENSChemoreceptors, osmoreceptors, mechanoreceptors -> (visceral afferents) -> CNS -> (visceral efferents) -> to local (intrinsic) nerve plexus -> Effectors: smooth muscle or glands, Response: change in contractile or secretory activity
Stimulation without food in stomachExternal stimuli (sight, smell, taste, thought of food) -> CNS -> (visceral efferents) -> local nerve plexus -> Effector: smooth muscle or glands, Response: change in contractile or secretory activity
(cephalic phase)

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