This lecture includes the anatomy of pancreas, structure of pancreas, parts of pancreas, its enzymes, trypsin, proteas and lipase and amylase, its functions, common bile duct, ucinate process, location of pancreas, pancreatic acinar cells, islet of langerhans and physiology of pancreas
2. INTRODUCTION
◦ Abdominal glandular organ with both digestive and hormonal functions.
◦ Pancreas is derived from the Greek word- “pan” – all and “kreas” – flesh.
◦ It is both an exocrine and endocrine gland
◦ SIZE- 15 to 20cm
◦ SHAPE: Oblong shape
◦ WEIGHT- 60-100 g
◦ LOCATION : posterior to the stomach with the head tucked into the curve of the duodenum. It is a retroperitoneal organ present
in the epigastrium and left hypochondriac region.
6. HEAD
◦ Widest part of the pancreas.
◦ Lies within the C shaped curve created by the
duodenum and is connected to it by connective
tissue.
7. UCINATE PROCESS
◦ A projection arising from the lower part of
the head and extending medially to lie beneath
the body of the pancreas.
◦ Lies posterior to the superior mesenteric
vessels.
8. NECK
◦ Located between the head and the body of
the pancreas.
◦ It overlies the superior mesenteric vessels
which form a groove
10. TAIL
◦ Left end of the pancreas that lies within close proximity
to the hilum of the spleen.
◦ Lies inside the peritoneum
11. PANCREATIC ACINAR CELLS
◦ The pancreatic acinar cell is the functional unit of exocrine pancreas.
◦ It synthesizes, stores and secretes digestive enzymes
◦ Under normal physiological conditions, digestive enzymes are activated only once they reach the duodenum.
◦ The acinar cells are triangular in shape and arranged in clusters
◦ It secretes digestive enzymes like:
◦ 1) Trypsin
◦ 2) Chemotrypsin
◦ 3) Amylase
12.
13. PANCREATIC ISLET CELLS
◦ Pancreatic islets are also called as the islets of Langerhans
◦ They form the region of pancreas that perform endocrine function
◦ They are scattered throughout the pancreas
◦ The normal human contains 1 million islets.
◦ The islets consists of 4 cell types
◦ 1) Alpha cells
◦ 2) Beta cells
◦ 3) Delta cells
◦ 4) F cells
14. HORMONES SECRETED BY ISLET CELLS
◦ 1) Alpha cells- it synthesize, store and secrete the hormone glucagon
◦ 2) Beta cells- produce and secretes insulin
◦ 3) Delta cells- secretes somatostatin
◦ F cells secrete pancreatic polypeptide that is released into the bloodstream after a meal, the endocrine function of which is not
known
15. PHYSIOLOGY OF PANCREAS
◦ Secretion of water and electrolytes originates in the acinar and intercalated duct cells
◦ Pancreatic enzymes originates in the acinar cells
◦ Final product is a colorless, odorless and isotonic alkaline fluid that contains digestive enzymes like amylase, lipase and trypsinogen
◦ 500 to 800 ml pancreatic fluid secreted per day
◦ Alkaline pH results from secreted bicarbonate which serves to neutralize gastric acid and regulate the pH of the intestine
◦ Enzymes digest carbohydrates, proteins and fats
16. ENZYMES
◦ 1. AMYLASE
◦ Only digestive enzyme secreted by the pancreas in an active form
◦ Functions optimally at a pH of 7
◦ Hydrolyzes starch and glycogen to glucose, maltose, maltotriose and dextrin
◦ 2. LIPASE
◦ Function optimally at a pH of 7 to 9
◦ Emulsify and hydrolyze fat in the presence of bile salts.
17. ◦ 3. PROTEASES
◦ Essential for digestion of protein
◦ Secreted by proenzymes and require activation for proteolytic activity
◦ Duodenal enzyme, enterokinase, converts trypsinogen to trypsin
◦ Trypsin in turn activates chymotrypsin, elastase, carboxypeptidase and phospholipase
18. INSULIN
◦ Synthesized by the B cells of the islets of Langerhans
◦ When the blood glucose level rises, insulin is produced to lower the blood concentration of glucose.
◦ It facilitates glucose transport across the plasma membranes.
◦ Insulin enhance the conversion of glucose to glycogen by glyconegenesis which is then stored in liver as a ready source of blood glucose.
◦ Conversion of glucose into fatty acids is enhanced by insulin
◦ 80% of the islet cell mass must be surgically removed before diabetes becomes clinically apparent
◦ Proinsulin is transported from the endoplasmic reticulum to the Golgi complex where it is packaged into granules and cleaved into insulin
and a residual connecting peptide C or C peptide.
◦ Major stimulants :
◦ - Glucose, amino acids, glucagon, etc
◦ Major inhinbitors:
◦ - Somatostatin, amylin, pancreastatin etc.
19. GLUCAGON
◦ Secreted by the A cells of the islet of Langerhans
◦ When the concentration blood glucose falls, glucagon stimulates the liver to convert glycogen to glucose (glycogenolysis) which
causes the blood glucose level to rise.
◦ It also stimulates gluconeogenesis formation of glucose from non carbohydrate sources
◦ Release of fatty acids and glycerol from adipose tissue is also stimulated by glucagon
◦ Both insulin and glucagon works against each other to maintain the blood glucose levels
◦ Glucagon elevates blood glucose levels through the stimulation of glycogenolysis and gluconeogenesis
◦ Major stimulant
◦ - Aminoacids, cholinergic firbers, beta sympathetic fibers
◦ Major inhibitors
◦ - Glucose, insulin, somatostatin and alpha sympathetic fibers
20. SOMATOSTATIN
◦ Secreted by the D cells of islet
◦ Functioning of both alpha and beta cells of islet is controlled by somatostatin
◦ Inhibits the release of growth hormone
◦ Inhibits the release of almost all peptide hormones
◦ Inhibits gastric , pancreatic and biliary secretion
◦ Used to treat both endocrine and exocrine disorders