Chapter 15 Gastrointestinal System Dr.LL Wang E-mail:wanglinlin@zju.edu.cn Rm 608,Block B,Research Building,School of Medicine,Zijingang Campus
Chapter 15 Gastrointestinal System Dr. LL Wang E-mail: wanglinlin@zju.edu.cn Rm 608, Block B, Research Building, School of Medicine, Zijingang Campus
Pancreatic Secretion Pancreas Pancreatic duct Bile duct Duodenum
Pancreatic Secretion
Copyright The McG Endocrine cells of pancreas Exocrine cells (secrete enzymes) -Duct cells (secrete bicarbonate) Pancreas Pancreatic duct Duodenum Common bile duct from gallbladder The exocrine cells in the pancreas play a central role in the production of digestive enzymes;the endocrine functions of the pancreas will be discussed at length in Chapter 16
The exocrine cells in the pancreas play a central role in the production of digestive enzymes; the endocrine functions of the pancreas will be discussed at length in Chapter 16
⑩Pancreatic juice ·pH7.8~8.4 ·~1500ml/day ·Isosmotic ·Components: -Pancreatic digestive enzymes:secreted by pancreatic acini -Sodium bicarbonate:secreted by small ductules and larger ducts
(I) Pancreatic juice • pH 7.8~8.4 • ~1500 ml/day • Isosmotic • Components: – Pancreatic digestive enzymes: secreted by pancreatic acini – Sodium bicarbonate: secreted by small ductules and larger ducts
Were digestive enzymes synthesized in their active form,they would digest the very cells that make them.Hence,inactive precursors(e.g.,trypsinogen)become activated(trypsin). Copyright The McGraw-Hill Companies,Inc.Perm required for reproductionor display. Pancreas Intestinal lumen Inactive enzymes Active enzymes Trypsinogen Trypsin Membrane bound enterokinase Epithelial cell
Were digestive enzymes synthesized in their active form, they would digest the very cells that make them. Hence, inactive precursors (e.g., trypsinogen) become activated (trypsin)
Secretion of bicarbonate ions -Secreted by the epithelial cells of the ductules and ducts that lead from acini Up to 145mmol/L in pancreatic juice(5 times that in the plasma) Neutralizing acid entering the duodenum from the stomach
• Secretion of bicarbonate ions – Secreted by the epithelial cells of the ductules and ducts that lead from acini – Up to 145mmol/L in pancreatic juice (5 times that in the plasma) – Neutralizing acid entering the duodenum from the stomach
Blood Ductule Lumen cells Na- Na Na' H (Active HCO 1→HC03 transport)H.CO3 (Active 。,transport) (Carbonic anyhydrase) HO + co ->C0 HO >H,0
Secretion of pancreatic digestive enzymes -Carbohydrates--Pancreatic amylase Pancreatic lipase -Fat Cholesterol esterase Phospholipase Trypsinogen -Proteins Chymotrypsinogen Procarboxypolypeptidase Proelastase
• Secretion of pancreatic digestive enzymes – Carbohydrates -- Pancreatic amylase Pancreatic lipase – Fat Cholesterol esterase Phospholipase Trypsinogen – Proteins Chymotrypsinogen Procarboxypolypeptidase Proelastase
x=alfa-amylase← (effect both amylases on starch) B=beta-amylase←— amylopectine Starches Pancreatic amylase dextrine omaltotriose Maltose and glucose polymers ◆glucose
Starches Maltose and glucose polymers Pancreatic amylase
Lipase eeserris Triglyceride Monoglyceride and fatty acids