Flashcards in GI-Phys Deck (80)
What is necessary for digesting fats?
What causes contraction of the GB?
What is an action of Secretin?
Stimulation of HCO3-
What causes Sphincter of Oddi to relax?
-->this allows bile and enzymes to flow to the duodenum
What determines the amount of bile salts the liver needs to produce?
Depends on the amount of bile salts reabsorbed
Where does carbohydrate digestion begin?
Mouth with salivary amylase
Where are disaccharides (sucrose, maltose, lactose, trehalose) digest?
What are simple sugars?
Where are simple sugars absorbed?
Intestine by sodium cotransport (SGLT) and facilitated diffusion (Glut 2)
What is the action of Incretin?
Increases secretion of Insulin
Where does protein digestion begin?
Stomach with activation of GI proteases
What converts Pepsinogen?
-HCL (low pH)-->converts to Pepsin
What does Pepsin do?
-Breaks down proteins into amino acids and oligopeptides
What is the action of Enterokinase?
-Converts Trypsinogen to Trypsin in the small intestine
-Trypsin activates other proenzymes secreted from pancreas into ACTIVE form
Who does the bulk of protein digestion?
Active Pancreatic enzymes
What are the final products of protein digestion?
How is protein absorbed?
-Na+-amino acid co-transport
-H+ di/tri-peptide co-transport
Where does fat digestion begin?
-Mouth with lingual lipase
Where are fats broken down?
Duodenum by digestive enzymes
What are the final products of lipids?
-Free fatty acids
Where are the final lipid products absorbed?
Jejunum via Michells and chylomicrons
What does B12 need to be absorbed in the intestine?
How are most water soluble vitamins absorbed?
How is B6 absorbed?
What kind of contractions are present in the UES and LES?
What is primarily responsible for increase tone of LES?
Loss of inhibitory enteric neurons--> achalasia
What is the progressive wave of muscle contractions that proceed along the esophagus, compressing the lumen and forcing food ahead called?
Nervous control of the GI tract would be impaired by damage to what?
Where does segmentation happen?
Where does peristalsis happen?
Where does haustration happen?
phasic contractions of long duration
Define mass movements
-Large infrequent peristaltic contractions, 1-3x/day
-Move contents over long distances, transverse colon-->sigmoid colon
Decreases peristalsis- "megacolon"
When does migrating motility complex occur?
-Periods of fasting to move undigested material from stomach down to colon
-Every 90-120 minutes during fasting
-Ability of the GI tract to contract even without nervous system input
What are the three layers of smooth muscle?
1. Outer longitudinal muscle
2. Inner circular muscle
3. Muscularis mucosa
What happens with longitudinal muscle contraction?
What happens with inner circular muscle contraction?
What stimulates enzyme secretion in the acing cells?
-CCK and ACh
What enzymes does the pancreas secrete?
What do ductal cells sense?
*Begin alkaline secretion
What does Gastrin stimulate?
-ECL to release histamine-->histamine acts on parietal cells to release HCL
What is the primary event of the gastric phase process?
What do peptides and amino acids in the food stimulate?
-G cells to release Gastrin
What does food block?
-Increases pH-->blocks stimulation of somatostatin secretion
what is the most important physiological antagonists of HCL secretion?
-->Released when pH falls below 3 to inhibit acid secretion
What activates histamine?
What does Omeprazole do?
Inhibit H+-K+ ATPase pump so H+ ions can't be secreted into stomach
Where is intrinsic factor from?
What happens as food moves into duodenum?
1. Enterogoastric Reflex-ACh release is inhibited (neural reflex) to STOP acid secretion
2. CCK and Secretin inhibit histamine release to further decrease acid secretion
are pancreas secretion isotonic or hypotonic?
What stimulates I cells?
Protein and fat in the duodenum
What do I cells release?
Increase pH of gastric venous blood after a meal (short lived)
Which phenomenon in salivary ducts explains why the final salivary secretion is hypotonic relative to the primary secretion of the acing cells?
-Absorption of more solute than water
What is the most important factor affecting salivary flow?
What gland contributes the most during stimulated salivary flow?
Parotid gland= very aqueous saliva
What gland contributes the most during unstimulated salivary flow?
Submandibular flow=more viscous
What carb must be digested before being absorbed by the small intestine?
Why do patients with diarrhea often have hypokalemia?
Faster chyme flow rate stimulates K+ secretion
How does V.Cholera cause diarrhea?
Increase cAMP levels
Resulting activation of cAMP or Ca2+ ?
Increased Cl- secretion
Act @ locations far away from the source
-Gastrin, CCK, Secretin
Released from nerves and act locally @ short distance
-VIP, somatostatin, NO,
What does Sympathetic release of Norepinephrine cause?
-Increased constriction of sphincters
What does Parasympathetics release of ACh cause?
What does Parasympathetics release of vasoactive intestinal polypeptide (VIP) cause?
Decreased constriction of sphincters
What does Parasympathetics of Gastrin-Releasing Peptide (GRP) cause?
What stimulates Secretin?
Acid entering duodenum
What is the action of secretin on stomach motility and secretions?
What is the action of Secretin at the Pancreas?
What stimulates CCK?
-Fat and amino acids entering duodenum
-Inhibits stomach motility and secretions
Ex: lactose intolerant
-Buildup of lactose in GI lumen holds water with it
-Associated w/ widespread destruction of absorptive epithelium
Deranged motility causing diarrhea
Ex: hypermotility in some cases IBS
What is the major site of sodium absorption?
What is the net result of fecal fluid?
Alkalotic and high K+