GIT Physiology Flashcards
For secretion, absorption & contraction of muscularis mucosae; Between submucosal and inner circular muscle layer
Submucosal Plexus/Meissner’s Plexus
For motility; Between inner circular & outer longitudinal muscle layers
Myenteric Plexus/Auerbach’s Plexus
Which layer is NOT seen in the esophagus?
Serosa
Strongest layer of the esophagus?
Submucosa
3 muscle layers are found in the stomach instead of two. What are theses muscle layers?
Inner obliqueMiddle circularOuter longitudinal
The myenteric plexus is mainly excitatory except for which regions?
Pyloric sphincter and Ileocecal valve
From G cells in the Antrum of Stomach; Increases Gastric H+ secretion
Gastrin
From S cells in the duodenum; Increases Pancreatic HCO3 secretions
Secretin
From I cells in the Duodenum & Jejunum; Stimulates GB contraction, sphincter of Oddi relaxation
Cholecystokinin (CCK)
From K cells in the Duodenum; Increases insulin secretion
Glucose-dependent Insulinotropic Peptide (GIP)
From M cells in the Duodenum & Jejunum; Stimulates in times of fasting
Motilin
Form of Gastrin is secreted in response to a meal
Little Gastrin (17 AA)
Form of Gastrin is secreted in the interdigestive period
Big Gastrin (34 AA)
Most potent stimuli for gastrin secretion
Phenylalanine, Tryptophan, Methionine
Neurocrine from vagus nerve to G cells
GRP/Bombesin
GI hormone classified as an Incretin
GIP, GLP-1
GI hormone responsible for interdigestive myoelectric complex
Motilin
Secreted by pancreas in response to CHO, CHON, lipids; Inhibits pancreatic HCO3 & enzymes
Pancreatic polypeptide
Secreted by intestinal cells in response to Hypoglycemia; Stimulates glycogenolysis and gluconeogenesis
Enteroglucagon
Secreted by cells throughout the GI tract in response to H; Inhibits release of ALL GI hormones, gastric H secretion
Somatostatin
Secreted by mast cells of gastric mucosa; Increases H secretion; potentiates gastrin and Ach action
Histamine
Inhibits appetite; Found on the Ventromedial Hypothalamus
Satiety Center
Stimulates appetite; Found at the Lateral Hypothalamic area
Appetite/Hunger Center
Sends signals to satiety & hunger center
Arcuate nucleus
Releases POMC to decrease appetite
Anorexigenic Neurons
Releases Neuropeptide Y to increase appetite
Orexigenic Neurons
Stimulates Anorexigenic Neurons, Inhibits Orexigenic Neurons
Lepton (Fat Cells), Insulin, GLP-1
Inhibits Anorexigenic Neurons
Ghrelin (Gastric Cells)
Inhibits Ghrelin
Peptide YY (PYY)
GI pacemaker
Interstitial Cells of Cajal
What is the most common stimulus for GI Peristalsis?
Distention
What is the Myenteric Reflex?
Muscles upstream contract, Muscles downstream exhibit Receptive Relaxation
What is the Law of the Gut?
Myenteric Reflex + Anal Direction of Peristalsis
How long does it take to transfer material from pylorus to ileocecal valve?
3-5 hours
How long does it take to transfer material from ileocecal valve to colon?
8-15 hours
Swallowing Center
Medulla
Triggers reflex when food is at the pharynx
Oral Phase
Soft palate pulled upward (closes nasopharynx), glottis covered (prevents aspiration), Upper Esophageal sphincter (UES) relaxes
Pharyngeal Phase
UES closes, Primary and Secondary Esophageal Peristalsis occurs
Esophageal Phase
Creates high pressure behind bolus of food propelling it towards the stomach; Accelerated by gravity
Primary Peristaltic Contraction
Clears Esophagus of remaining food
Secondary Peristaltic Contraction
Capacity of Stomach
1.5L
Increases distensibility of orad stomach
CCK
Contraction of caudad stomach and pyloric sphincter
Retropulsion
Propelling food from stomach to duodenum
Gastric Emptying
Duration of Gastric Emptying
3 hours
Back-and-forth movement with no net forward motion; Mixes chyme with pancreatic enzymes
Segmentation Contraction
Propels chyme towards large intestines
Peristaltic Contraction
Saclike segments due to segmental contractions of the large intestines
Haustra
Colon: For absorption of water
Proximal Colon
Colon: For storage of Feces
Distal Colon