GI Flashcards
4 layers of GI Tract
Mucosa
Submucosa
Muscularis
Serosa
Meissner Plexus and Auerbach Plexus
Meissner=Submucosal Plexus
Senses environment in lumen; regulates blood flow; unfolding of wall in stomach
Auerbach=Myenteric
Peristolsis; movement
Parasympathetic Role in GI
-secretion, motility, pain sensation, intestinal reflexes
Secretes ACh = excites GI
Sympathetic Role in GI
-inhibits motility, produces vasoconstriction
Secrete norepi and epi = inhibits GI
Action Potential of GI
Nerve = Na+ channels only so no AP reached GI = special channels that let Na+ and Ca++ to enter leading to Sloooww and drawn out AP (like cardiac)
Splanchnic Flow
- Blood flow from GI ALL go through the hepatic portal vein to clean up the blood and remove trash
- Fats Do NOT go this route
Contents of Saliva
1L per day, hypotonic, pH of 6.0-7.0 water mucus bicarbonate potassium salivary amylase lingual lipase chloride, sodium, IgA
Cephalic Phase
SALIVATION activated by PNS and SNS
- Sour, smooth, sweet, soft = excite
- Food contacts epithelium in mouth
- Irritation/nausea – saliva increases to remove irritant
- Also by insulin secretion in hyperglycemic environment (not if normoglycemic)
- Aggression
Process of chewing/swallowing
- Food enters mouth; mixed with saliva
- Bolus moved by tongue and propelled back and upward
- Pharynx muscles raise soft palate to nasal cavity
- Respiration inhibited by the medulla swallowing center
- Epiglottis slides back to close off the larynx and trachea
- Upper Esophageal Sphincter relaxes and food enters esophagus
Apthous ulcers
disruption in mucosal layer from from trauma, infection or inflammation
What special nerve works on the esophagus?
Vagus
UES
Upper Esophageal Sphincter
keeps air out
LES
Lower Esophageal Sphincter
keeps gastric juices in stomach
Esophageal Stricture and Rings
- Narrowing of esophagus from scar tissue
- Bands of esophageal muscle tissue forming in the lower esophagus
- Both associated with GERD
Achalasia
LES fails to relax
- increase of sympathetic tone of LES
- prohibits food from entering the stomach
- Esophageal swelling, infection, ulceration
3 Regions of the stomach
fundus, body, pylorus
Location and function of pyloric sphincter?
Located at distal end of the stomach; keeps food in the stomach for digestion
Oxyntic Glands
Found in fundus and body of the stomach
Parietal Cells
HCl Intrinsic factor (needed for B12)
Chief Cells
pepsinogen; requires HCl to split to pepsin
ECL cells
secrete histamine; stimulates gastric acid secretion
D cells
secrete somatostatin; inhibits gastrin-gastric acid
G cells
G cells secrete gastrin; stimulates gastric acid secretion
Mucous neck cells
secrete mucus; Goblet cells
Pyloric glands
In pylorus (antrum) Contain G cells, D cells, and mucous neck cells
surface mucous cells
everywhere; special mucous cells secrete an abundance of viscid mucus. Protective, coats 1 mm thick. Very alkaline. Increases with proximity of food to epithelium
Stimulation of HCl acid secretion
histamine, gastrine, ACh, somatostatin
Where are carbs, proteins, and fats digested?
carbs = saliva proteins = stomach/small intestine with pepsin and HCl fats = lingual lipase that's activated in stomach and small intestine
Gatroileal Reflex
gastric motility and secretion increase; gastroileal reflex increases motility
Gastroenteric reflex
distention of the stomach triggers peristalsis
Gastritis
Permeability of mucus layer allows digestive enzymes to attack mucosa. Helicobacter Pylori decreases mucosal barrier and increases acid secretions.
Gastric and Duodenal Ulcers
mucosal membrane gone; HCl irritating submucosa
Tx: H2 blocker b/c you want to block histamine which STIMulates HCL secretion.
Adventitia vs Serosa
Adventitia = outer layer/connective tissue of esophagus; stronger for better protection because it is RETROperitoneal Serosa = outer layer/connective tissuee of the rest of the GI; on intraperitoneal structures
Rugae
increase absorption but not pressure; increase capacity
Cephalic - Gastric - Intestinal Phases
Phases of digestion
Brunner’s Glands
in duodenum; secrete alkaline mucosa to neutralize acid from stomach
Crypts of Lieberkahn
Secrete digestive juices, hold undifferentiated cells to replace epithelial population every 4-7 days
I cells
Secrete Cholecystokinin which slows gastric emptying and increases bile ejection
ileogastric reflex
distension of the ileum inhibits stomach motility
enterogastric reflex
stretch receptors in the duodenum send a message to slow or stop emptying of the stomach
Gastrocolic reflex
stretch in the stomach causes an increase in colonic motility
Gastroileal reflex
increased motility in the stomach causes increase in motility of the ileum
CCK, Pepsin, Secretin inhibit what?
Parietal, chief, and perstalsis
Pancreatic enzymes
trypsinogen
chymotrypsin
procarboxypeptidase
What does pancreatic amylase digest?
carbohydrates
What digests fats?
pancreatic lipase, lingual lipase, bile
What digests carbohydrates?
pancreatic amylase and HCl
What digests protein?
pancreatic enzymes
Micelle formation
little fat packets created by bile salts; transported to liver; bile salts go back in to circulation
Enterohepatic circulation
bile returns to liver to be reused
Ca++ Absorption
- absorbed in ileum
- absorption enhanced by bile salts; which also helps absorb Vit D
- Increase demand=increased uptake
Vitamin B12 Absorption
- absorbed in ileum
- B12 absorbed with the help of INTRINSIC FACTOR
- Necessary for erythrocyte maturation
PERNICIOUS ANEMIA (not B12)
Iron
- Vit C enhance absorption
2. Get it from hemoglobin and myoglobin in animal
