1. Physiological functions of pancrease & large intestine
Digestive Physiology
By: M.H.Dashti
Lecture 4
Physiological functions of pancrease & large intestine

2. Digestion & Absorption of Fat products in Small Intestine

3. Final Digestion & Absorption in Of Carbohydrates in Small Intestine
Monosaccharides leave the basolateral Membrane via GLUT-2

4. Final Digestion & Absorption of Protein products in Small Intestine

5. Chemical Digestion in Small Intestine: Nucleic Acids
Pancreatic juice convert RNA & DNA to Nucleotides by Ribonuclease & Deoxyribonuclease
brush border enzymes (nucleosidease and phosphatase) converts Nucleotides to pentose, phosphate & nitrogenous bases

6. Absorption of vitamin B12

7. absorption of Fe2+ in small intestine
iron transporter DMT1, heme transporter (HT), heme oxidase (HO) , ferroportin (FP) ,hephaestin (Hp), transferrin (TF)

8. absorption of Ca2+ in small intestine is controlled by vitamin D3

9. Sodium absorption in ileum is coupled to choloride absorption
Sodium absorption in jejunum is coupled to glucose , amino acid & bicarbonate absorption
Sodium absorption in ileum is coupled to choloride absorption

11. Absorption of Water 9 liters of fluid dumped into GI tract each day
Small intestine reabsorbs 8 liters
Large intestine reabsorbs 90% of that last liter
Absorption is by osmosis through cell walls into vascular capillaries inside villi

12. Where will the absorbed nutrients go?

13. Ileocecal sphincter Controlled by pressure differences Neural events
Ileo -colic & colono-ileal reflexes
Ileo- gastricic & gastro-ileal reflexes
Ileal break
Oxyntomodulin & neurotensin

14. Anatomy of Large Intestine
5 feet long by 2½ inches in diameter
Ascending & descending colon are retroperitoneal
Cecum & appendix
Rectum = last 8 inches of GI tract anterior to the sacrum & coccyx
Anal canal = last 1 inch of GI tract
internal sphincter----smooth muscle & involuntary
external sphincter----skeletal muscle & voluntary control

15. Digestion in Large Intestine
No enzymes are secreted only mucous
Bacteria ferment
undigested carbohydrates into carbon dioxide & methane gas
undigested proteins into simpler substances (indoles)----odor
turn bilirubin into simpler substances that produce color
Bacteria produce vitamin K and B in colon

16. Absorption & Feces absorption in the Large Intestine
Some electrolytes---Na+ and Cl-
After 3 to 10 hours, 90% of H2O has been removed from chyme
Feces = dead epithelial cells, undigested food such as cellulose, bacteria (live & dead)

17. Large intestine motility
Haustral churning
BER (3 to 18/min)
haustral shuttling
Multihustral contraction in ascending colon
Mass movement
Mainly starts in the pacemaker site at the beginning of transverse colon
Affected by gastrocolic reflex
Defecation reflex
Local & central
Gostric stimulation (activates gastrocolic reflexes)
Feces
Stimulation of local defecation reflexes
Stimulation parasympathetic controlled defecation reflexes
Rectum
Moss movements
Colon
Presence of chyme in the duodenum
Duodenocolic stimulation (activates Duodenocolic reflexes)
Presence of food in the stomach
Stomach

18. Defecation Gastrocolic reflex moves feces into rectum
Stretch receptors signal sacral spinal cord
Parasympathetic nerves contract muscles of rectum & relax internal anal sphincter
External sphincter is voluntarily controlled

19. Pressures in the Rectum

20. Neural pathways of defecation reflex