Pancreas is a retroperitoneal organ, composed of both endocrine and exocrine tissue.
Pancreas soft, spongy, grayish pink retroperitoneal gland.
Size and Weight of Pancreas
Length - 12-15 cm (5-6 inch) long, 2.5 cm (1 inch ) thick.
Weight - 90 gms
Location of Pancreas
It stretches across back of abdomen, behind the stomach.
Head of pancreas is on right side of the abdomen and is connected to duodenum through small tube called pancreatic duct.
Abdominal aorta and inferior venacava lie behind the head of the Pancreas.
Anatomy of Pancreas
Pancreas consist of -
1. Head
2. Body
3. Neck
4. Tail
1. Head (Broadest part)
Head of pancreas lie on the right of abdominal cavity and fit into C-shapes curve of duodenum. Head of pancreas is the widest part of pancreas.
2. Body (Main part)
Body of pancreas lies between head and tail.
3. Neck
Neck of pancreas is slightly constricted part (thin) of pancreas between head and body.
4. Tail
Tail of pancreas is narrow end of pancreas, extend left side of body lie in front of left kidney and extends to the left to spleen.
Microscopic Anatomy of Pancreas
Pancreas have an Endocrine part and Endocrine part.
Exocrine Part of Pancreas
Exocrine part of pancreas consist of group Acini; arranged like grapes (cells arranged in cluster).
99% of pancreatic cell are acinar cells, only 1% is endocrine cells.
Acinar cells secrete mixture of fluids and digestive enzyme called pancreatic juice into the small intestine. It produces produce 1.5 liter of digestive juice daily.
Endocrine Part of Pancreas
Endocrine parts of pancreas consist of islets; cluster of cells within pancreas, called islets of Langerhans. This region of pancreas contain its endocrine part (hormone-producing) cells. It secretes insulin, glucagon and other hormones.
Pancreas Island
Islets of Langerhans contains cells -
1. Beta cell
2. Alpha cell
3. Delta cell
1. Beta Cell
Beta cells produce insulin.
About 70% are beta cells (largest number of cell), mostly localized in the core of the islet. Beta cells are surrounded by alpha cells that produce glucagon, smaller numbers of delta cells that produce somatostatin, and PP cells that produce pancreatic polypeptide .
Beta cells also produce Amylin hormone, helps in controlling our appetite (eating behaviour).
Amylin hormone inhibit the glucagon secretion, it delay gastric emptying act as satiety.
2. Alpha Cell
Alpha cells produce glucagon. About 17% are alpha cells.
3. Delta Cell
Delta cell produce Somatostatin. About 7% are Delta cells.
Delta cells inhibit secretion of other pancreatic hormone with as insulin and glucagon.
4. Pancreatic Polypeptide (PP cell)/ Gamma cells/ F cells
PP cells secrete pancreatic polypeptide (PP). PP cells inhibit somatostatin, gall bladder contraction and secretion digestive enzyme by pancreas.
5. D1 Cells
Duct of Pancreas
Duct of pancreas or duct of Wirsung joining the pancreas to common bile duct. Pancreatic secretion pass from the secreting cells in the pancreas into the small duct. Small duct unite to form two larger duct that convey the secretion into the small intestine.
Pancreatic Duct
Larger of the duct is pancreatic duct. Pancreatic duct carry digestive enzyme toward the duodenum via via the ampulla of Vater (major papilla). Pancreatic duct begins at the tail and run through the body to the head.
Pancreatic duct joins the common bile duct from the liver and gal bladder and enters the duodenum. Common duct called Hepatopancreatic ampulla. Duodenal opening of ampulla is controlled by sphincter of oddi. Sphincter of oddi; control flow of juice through duct from the liver and pancreas into the duodenum.
Accessory Pancreatic Duct
Accessory pancreatic duct begin in lower part of head. It entering the duodenum at the minor duodenal papilla. Small amount of pancreatitic enzyme passes into duodenum.
Pancreatic Juice
Pancreatic Juice consists of -
1. Clear, colorless liquid
2. Strongly alkaline
3. Lipase; enzyme works together with bile, produced by liver, to break down fat in diet.
4. Protease; enzyme breaks down proteins in diet.
5. Amylase; enzyme helps break down starches.
Pancreatic secretes 1.5 liter pancreatic juice daily.
Pancreatic Juice Components
Pancreatic Juice two main component-
1. Aqueous component
2. Ezymatic component
1. Aqueous component
Aqueous component produced by columnar epithelial cells. It contains water, sodium, potassium, bicarbonate ions (major component).
Sodium bicarbonate gives pancreatic juice a slightly alkaline pH ( 7.1 - 8.2) that buffers acidic gastric juice in chyme. They neutralize acidic chyme that enters the small intestine from stomach.
2. Enzymatic component
Enzymatic component secreted by acinar cell of the pancreas for the final digestion of protein, CHO and lipids.
Such as Elastase, Phospholipase, Pancreatic lipase, Pancreatic amylase, Ribonuclease and Deoxyribonuclease, Pancreatic proteolytic enzyme.
1. Pancreatic Lipase
Pancreatic lipase is principal triglyceride digestive enzyme in adult body. It splits triglycerides into; smaller, absorbable glycerol, free fatty acid.
2. Pancreatic Amylase
Pancreatic amylase converts polysaccharides into disaccharides into, monosaccharides (CHO digestive enzyme).
3. Ribonuclease and Deoxyribonuclease
It converts nucleic acids into mononucleotide (Nucleic acid digestive enzyme).
4. Pancreatic proteolytic enzyme
These consist of-
Trypsinogen
Chymotrypsinogen
Procarboxypeptidase
(Secreted in inactive form).
Trypsinogen activated to trypsin by activating enzyme enterokinase secreted by small intestine mucosa.
Chymotrypsinogen and procarboxypeptidase are activated into their active forms chymotrypsin and carboxypeptidase in intestinal lumen by newly formed trypsin.
Another group of enzymes secreted by Pancreas are -
6. Elastases
Elastases primary role is the breakdown of elastin that cause destruction of elastic tissue of blood vessels.
Elastase enzyme helps break down carbohydrates, fats and proteins after eat.
7. Phospholipases
Phospholipases enzyme degenerates membrane phospholipid.
Function of Pancreas
1. Produce glucose
2. Produce insulin
3. Converting food into energy
4. Produce somatostatin
5. Make pancreatic juice (breakdown sugar, fat, starch)
6. Regulation of blood sugar level
7. Making hormone and enzyme
Amylase; for carbohydration breakdown
Lipase; for fat breakdown
8. Pancreatic duct travel; enzyme to small intestine
9. Endocrine function; that regulates blood sugar
10. Exocrine function that help in digestion
12. Produce pancreatic juice
13. Neutralize acidic chyme
Regulation of Pancreatic Secretion
Pancreatic secretion regulated by both-
1. Nervous mechanism
2. Hormonal mechanism
Taste buds detect food in mouth (during cephalic phase) and gastric phase of gastric digestion.
They send impulses to the brain, then stimulates
Pancreas by transmitting parasympathetic impulses, and vagus nerve to pancreas.
Result increased secretion of pancreatic juice
When acidic chyme enter the small intestine
Enteroendocrine cell in small intestinal mucosa released secretin (by duodenum)
Enteroendocrine cells also secrete CCK (cholecystokinin) facilitating digestion with in small intestine
CCK stimulates a pancreatic secretion rich in digestive enzyme
Secretin stimulates flow of pancreatic juice that is rich in bicarbonate ions
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