DI Processes to be reviewed (already studied by paper)

Question 1

Digestive system process (IMSDAD)

Answer 1

ingestion, motility, secretion, digestion, absorption, defecation

Question 2

Organization of GI tract neural

Answer 2

Short reflexes: intrinsic, within GI tract, enteric path
- stimuli → receptors → plexus → effector → response

Long reflexes: extrinsic, outside GI tract, CNS path
- afferent → receptors to CNS
- efferent → autonomic motor (sympathetic and parasympathetic) of CNS → plexuses

Question 3

Forming stomach acid (HCl)

Answer 3

1. H2O + CO2 -> H2CO3 -> H + HCO3
2. HCO3 secondary active transport (counter) with Cl across basolateral membrane for Cl to enter epithelial cell. Then Cl uses FD to cross apical membrane into stomach lumen
3. H engages in primary active transport with potassium to cross apical membrane into stomach lumen
4. H and Cl are now in stomach lumen to form HCl
5. Potassium goes back into stomach lumen by FD to continue process of primary active transport with H (a way to keep H leaving epithelial cell)

Question 4

Regulating acid level in stomach

Answer 4

1. If gastrin (hormone), histamine (paracrine) or acetylcholine (neurotransmitter) released
   -bind on basolateral membrane
   -increase # secondary messengers
   -increase number of hydrogen potassium pumps inserting on apical membrane
   -increase stomach acid in stomach lumen
2. if somatostatin (hormone) released
   -bind on basolateral membrane
   -decrease # secondary messengers
   -decrease # of hydrogen potassium pumps inserting on apical membrane
   -decrease stomach acid in stomach lumen

Question 5

Small intestine fat absorption

Answer 5

1. Emulsification
   -fat globule -> small amounts of triglycerides coated in bile salts and phospholipids (polar side out to prevent reforming fat globule) = emulsification droplets
2. allows more SA for pancreatic lipase digestive action which breaks down triglycerides into free fatty acids and monoglycerides
3. monoglycerides and free fatty acids cross apical membrane by simple diffusion but too many and risk triglycerides being reformed which is where micelles come into play
   -micelle: individual free fatty acids or monoglycerides coated in bile salts and phospholipids with polar side facing out (same logic as ED). They stay near apical membrane to be ready for easy simple diffusion when broken down
4. once inside epithelial cell, triglycerides reformed and phospholipids + cholesterol coat to form chylomicrons
   -chylomicrons are in a vesicle or sac and fuse to basolateral membrane
   -basolateral membrane then opens up and exocytosis occurs where chylomicrons go into IF and then find their way to enter lacteals (lymphatic capillaries) as they’re too big for blood capillaries