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

Digestion & Absorption of Fat products in Small Intestine

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

Final Digestion & Absorption of Protein products in Small Intestine

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

Absorption of vitamin B12

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

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

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

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

Where will the absorbed nutrients go?

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

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

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

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)

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

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

Pressures in the Rectum

Neural pathways of defecation reflex