Digestive System

-motility
-secretion
-digestion
-absorption
-protection
-excretion

-upper and lower esophageal sphincters
-pyloric sphincter
-spinchter of oddi (between pancreas and duodenum

-illeocecal valve
-internal and external sphincters of the rectum

-swallowing reflex
-tonic contractions
-phasic contactions
-slow-wave potentials
-mass movement

-initiation is conscious, everything else is automatic

-sustained contraction for minutes or hours
-occurs in smooth muscle sphincters and anterior portion of stomach
-keeps bolus from moving backwards

-Peristalisis
-Segmentation
-Migrating motor complex

movement of bolus forward (mouth to anus)

-mixes contents through combined contraction at intervals

-creates net movement of material thorugh system

enables backward movment of colonic bolus back toward ilium (occurs anywhere in alimentary canal)

help organize peristalsis and segmentation

-interstitial cells of Cajal

stronger version of peristalsis (in the colon) helps moves things toward the rectum (helps trigger the defecation reflux)
occurs 3-4 times a day

migrating motor complex
pattern of electrical and musclular activity in stomach and small intestine during fasting (in between meals)
purpose: cleans out GI tract, sweeps things toward colon, prevents bacterial overgrowth

eating (results in normal peristaltic acitivity)

-action potential must be overcome

endocrine/paracrine/neurocrine
and
neural regulation

-neural regulation

-enteroendocrine cells (in epithlial lining of gut)
-enterochromaffin cells
-enterochromaffin-like cells

don't have luminal surface, located on the basal side of other cells, does limit their ability to detect things to some extent

serve as "brain-gut peptides" facilitate gut brain communication

-myenteric plexus
-teritary plexus
-submucosal plexus
-deep mucosal plexus
-mucosal plexus

-brain subconsciously initats gut action based on environmental stimuli
*signal goes to medulla oblongata, preganglionic parasympathetic neuron in vagus nerve responds, whie postganglionic parasympathetic and intrinsic enteric neuron responds

smooth muscles
endocrine cells of stomach
pancreas
intestines

gastrin (released by G cells)

-peptides and amino acids, considered a neural relex

ECL (centerochromaffin like cells) and parietal cells

stimulates gastric acid secretion and mucosal growth

stomatostatin

Cholecystokinin CCK)
Secretin
Motillin
Gastric Inhibitory Peptide (GIP)
Glucagon-like peptide-1 (GLP-1)

stands for Cholecystokinin
digestive hormone released in intestine

stands for Gastric inhibitory peptide
digestive hormone released in intestine

stands for Glucagon-like peptide-1
digestive homrone released in intestine

CCK (cholecystokinin)
stimulated by fatty acids and some amino acids

-acid in small intestine

-fasting, there is periodic release every 1.5-2 hrs

GIP=gastric inhibitory peptide
glucose, fatty acids, amino acids in small intestine

GLP-1= glucagon-like peptide-1
mixed meals with carbohydrates or fats in the lumen

CCK cholecytokinin: gallbladder, pancreas, stomach

pancreas and stomach

gastric and intestinal smooth muscle

GIP= gastric inhibitory peptide
beta cells of pancreas

GLP-1= glucagon-like peptide-1

-stimulates gallbladder contraction and pacreatic enzyme secretion
-inhibits gastric emptying and acid secretion

stimulates bicarbonate secretion
inhibits gastric emptying and acid secretion

-stimulates migrating motor complex (MMC)

stimulates insulin release
inhibits gastric emptying and acid secretion

stimulates insulin release
inhibits glucagon release and gastric function

GIP: targets beta cells of pancreas
GLP-1: targets endocrine cells of pancreas

-CCK (cholecytokinin)
-GLP-1 (glucagon-like peptide-1)

enterochromaffin cell

Motillin (stimulates MMC)

-cephalic
-oral
-esophageal
-gastric
-intestinal
-colonic

-saliva
-bile secretion
-gastric secretion
-pancreatic secretion
-intestinal secretion

9 L
2 from food and drink
the other 7 from digestive organs (gall bladder, salivary glands, stomach, pancreas, intestines)

7.5 L absorbed from small intestine
1.4 L absorbed from large intestine
toatl 9 L

-mouth
-stomach
-intestine

-mucous cells in stomach
-serous cells in salivary glands
-goblet cells in intestine

main structural component of mucous (protein based)

-bile
-bile salts
-bile pigments
-cholesterol

-stores and concentrates bile

-hepatic duct
-common bile duct

-gel that form glycoproteins
-contains cystine domains

circular regions containing serous cells that secrete salts

its not isotonic to interstital fluid
-there's more K
-less NA+ and CL-

-CFTR channel

Cl- entering the lumen from cells dividing the lumen and interstitial fluid