GI system Flashcards
General Gut Layers
Mucosa - epithelium, lamina propria, muscularis mucosae
Submucosa - Submucosal glands, blood vessels, submucosal nerve plexus
Muscularis - Inner circular layer, Myenteric nerve plexus, outer longitudinal layer
Serosa or Adventitia
Mucosa
Epithelium
Lamina propria
Muscularis mucosa - smooth muscle that expels gland contents, not involved in movement of bulk
Submucosa
Dense irregular CT
Large blood vessels
Meissner’s Submucosal Enteric Nerve Plexus - regulates mucosal epithelium and muscularis mucosa
Muscularis externa
Smooth muscle - usually 2 layers. Skeletal muscle in pharynx, upper esophagus and external anal sphincter
Auerbach’s Enteric Plexus - nerves found between muscle layers, regulates motility
Serosa or Adventitia
Serosa - mesothelium covering on more mobile regions (suspended in a cavity)
Adventitia - CT covering on more rigid regions
Pharynx
Mucosa is stratified squamous non-keratinized
Lacks muscularis mucosae and submucosa
Irregularly arranged skeletal muscle
Coated in adventitia
Esophagus
Upper 1/3 is voluntary, lower 2/3 involuntary, involved in peristalsis
Contains esophageal glands in submucosa
Coated in adventitia
Stomach
Simple columnar epithelium
Adds acid to food to create chyme
Secretes lipase to digest triglycerides
Secretes pepsin to digest proteins
Esophagitis
Inflammation of esophagus from acid regurgitated through upper esophageal sphincter
GERD
Gastro-Esophageal Reflux Disease - chronic esophagitis
Barrett Esophagus
Intestinal metaplasia of esophageal epithelium. Becomes simple columnar epithelium with lots of goblet cells. Looks like colon. Can develop into adenocarcinoma.
Control of digestive activities
Neural control
Local factors
Hormone control
Pits and glands
Inside of stomach
Pits are openings that vary in depth
Glands are located at the bottom of pits
Pit depth and gland location/type can help you determine where a tissue sample comes from.
Cardia
Pits shorter than glands, glands almost all mucous
Body and Fundus
Long glands with parietal and chief cells
Pyloris
Glands mostly mucous, longer pits
Mucous neck cell
Lines pits, secretes mucous and bicarbonate
Parietal Cells
Secrete Gastric acid (HCl) and Gastric Intrinsic factor for vitamin B12 and Ca2+ absorption.
Unique “fried egg” appearance makes them easy to identify.
Enterochromaffin-like Cells
Secrete histamine to stimulate acid production
Chief cells
Secrete pepsinogen and gastric lipase
D cells
Secrete somatostatin to inhibit acid production
G cells
Secrete gastrin to stimulate acid production
DNES
Diffuse neuroendocrine system
APUD
Amine Precursor Uptake and Decarboxylation
DNES cells secrete what?
Gastrin, glucagon, histamine, gherlin, somatostatin, serotonin
Parietal Cell Acid Secretion
Carbonic anhydrase catalyses water and CO2 into H+ and HCO3-.
HCO3- is transported out basally
H+ and Cl- pumped out Apically
H+ and Cl- join to become HCl
Control of parietal cell acid secretion
Gastrin from G cells and histamine from enterochromaffin-like cells secrete HCl
Cephalic control - 30%, smell taste, conditioning - Vagus nerve
Gastric control - 60%, distension (vagus), Distension of antrum (local reflex), amino acids, small peptides (gastrin)
Protective factors of GI epithelium
HCO3- and mucus, prostaglandins, mucosal blood flow, growth factors
Damaging factors of GI epithelium
H+ and pepsin, H. pylori, NSAIDs, stress, smoking, alcohol
Gastric movements
- Propulsion
- Grinding
- Retropulsion
Peristalsis
Move food along tract
Segmentation
Alternate contraction mixes and moves food
Peptic ulcer
Break in mucosa of stomach
Gastric adenocarcinoma
Dysplasia of stomach mucosa
