Structure and Function of Accessory Organ-4

Pancreas

The pancreas is a soft, spongy, grayish gland that is external to the peritoneal cavity and located posterior to the great curvature of the stomach. It measures 12 to 15 cm in length and weighs 60 gm. It is located in the left hypochondriac and epigastric regions of the abdominal cavity. It has a head, a body, and a tail.

• Head: Resides in the duodenum's concave curvature.
• Body: Lies behind the stomach and reaches the spleen.
• Tail: Is a little area that touches the spleen and is located in front of the left kidney.

Structure of the Pancrease

An endocrine and an exocrine gland, the pancreas. The pancreatic islets, which are small clusters of secretory cells dispersed throughout the remaining pancreatic tissue, perform its endocrine function. The islets, also referred to as islets of Langerhans, are dispersed all over the pancreas but are concentrated mainly in the tail area. The hormones of glucose metabolism, insulin and glucagon, are secreted by the islet cells.

Exocrine tissue, which makes up the majority of the pancreas, secretes 1200 to 1500 cc of pancreatic juice daily. The lobules of the exocrine pancreas are made up of acini, which are secretory units (alveoli). Cuboidal epithelial cells encircling a duct lumen make up an acinus. The many pancreatic ducts empty pancreatic juice into the duodenum. One of these, the larger pancreatic duct, connects to the CBD and passes through the duodenum as the ampulla of Vater, a dilated common duct. The auxiliary duct may separate openings into the duodenum. The sphincter of Oddi, a group of smooth muscle, controls the flow of bile and pancreatic juice through the ampulla of Vater into the small intestine.

Pancreatic Juice

The pancreatic juice, an alkaline mixture of water, electrolytes (particularly sodium bicarbonate), enzymes, and zymogens, is the exocrine secretion of the pancreas. Each day, the pancreas produces 1200–1500 ml of pancreatic juice. The pancreas produces inactive versions of its protein-digesting enzymes. Therefore, they do not digest the pancreas' own cells. Enterokinase, an activating enzyme, causes these enzymes to become active as they enter the small intestine. These are the main components:

• Sodium bicarbonate-neutralizes HCL of gastric juice
• Zymogens (enzyme precursor proteins)-their active forms digest proteins

• Trypsinogen trypsin
• Chymotrypsinogen-chymotrypsin
• Procarboxypeptidase-carboxypeptidase

• Other enzymes:
  • Pancreatic amylase-digests starch
  • Pancreatic lipase-digests fat
     
• Ribonuclease-digests RNA
• Deoxyribonuclease-digests DNA

Regulation of Secretion of Bile and Pancreatic Juice

In response to a meal, bile and pancreatic juice are secreted. Additionally, the vagus nerve induces pancreatic secretion. Chyme stimulates the secretion of enterogastrone, a hormone complex made up of secretin and cholecystokinin, as it enters the duodenum.

Cholecystokinin stimulates three processes:

• Gall bladder contraction pushing bile into the CBD.
• Pancreatic enzyme secretion.
• Release of bile and pancreatic juice into the duodenum due to relaxation of the sphincter of Oddi.

The pancreatic ducts and hepatic bile ducts are stimulated by secretin to produce more bicarbonate. Therefore, bile and pancreatic juice both contain more bicarbonate and efficiently neutralize the acid in chyme.

Function of the Pancreas:

An endocrine and an exocrine gland, the pancreas.

• The pancreas' exocrine function is to produce pancreatic juice, which aids in the digestion of proteins, carbohydrates, and fats.
• The pancreas's secretion of the hormones insulin and glucagon, which regulate blood glucose levels, is part of its endocrine function.

Blood supply

The pancreas receives arterial blood from the splenic and mesenteric artery, and the splenic and mesenteric vein drains venous waste into the portal vein.