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Pancreatitis- Anatomy and physiology of Pancreas

Pancreatitis is the inflammation of the pancreas, an organ that produces several enzymes to aid in the digestion of food, as well as the hormone insulin, which controls the level of sugar (glucose) in the blood. Although the mechanisms causing pancreatic inflammation are unknown, pancreatitis is commonly described as Autodigestion of the pancreas. Generally, it is believed that the pancreatic duct becomes obstructed, accompanied by hypersecretion of the exocrine enzymes of the pancreas. These enzymes enter the bile duct, where they are activated and, together with bile, back up (reflux) into the pancreatic duct, causing pancreatitis.

Mild attacks of acute pancreatitis can get better on their own, or by changing the diet. In the case of recurring pancreatitis, however, long-term damage to the pancreas is common, sometimes leading to malnutrition and diabetes.

 

RELATED ANATOMY AND PHYSIOLOGY

Anatomy

Pancreas is an organ situated in the upper part of one’s abdomen, behind the stomach. It is in the retroperitoneal, 2nd lumbar vertebral level and extends in oblique and transverse direction. It is about 6 inches or 15 cms long and is about 60-100 gram in weight.

There are 3 parts of the pancreas

  1. Head- It has a flattened bulbous head that is surrounded by part of the intestine called Duodenum.
  2. Neck- It is superiorly related to the pylorus.
  3. Body- A narrow body that lies behind the stomach.
  4. Tail- A tapered tail that rests on the front of the left kidney.

Pancreatic duct

Pancreatic duct, or duct of Wirsung (also, the Major pancreatic duct due to the existence of an accessory pancreatic duct), is a duct joining
the pancreas to the common bile duct to supply pancreatic juices which aid in digestion provided by the “exocrine pancreas”. The pancreatic duct joins the common bile duct just prior to the ampulla of Vater, after which both ducts perforate the medial side of the second portion of the duodenum at the major duodenal papilla.

Histology of Exocrine Pancreas

It has 2 major components

  • Acinar cells: They constitute 80%-90% of the pancreatic mass. Acinar cells secrete the pancreatic enzymes. About 20-40 acinar cells coalesce into a unit called Acinus. Centroacinar cells(2nd type in the acinus) is responsible for fluid and electrolyte secretion by the pancreas.
  • Ductular system: Network of ducts that carry the exocrine secretions into the duodenum. Intralobular ducts contribute to fluid and electrolyte secretions along with Centroacinar cells.

Histology of Endocrine Pancreas

It account for only 2% of the pancreatic mass. It contains next of cells called the Islets of Langerhans. The endocrine pancreas has 4 major cell types

  1. Alpha (A) cells secretes glycogen
  2. Beta (B) cells secretes insulin
  3. Delta (D) cells secretes somatostatin
  4. F cells secretes pancreatic polypeptide

The B cells are centrally located inside the islet and are 70% of the islet mass. The others cells are located at the periphery of the islet.

Physiology or Function

Pancreas is one of the organs in the body that has both exocrine and endocrinal functions. The function of the pancreas is to make digestive enzymes which digest food materials in the small intestines. In addition the pancreas also makes insulin which controls the blood glucose levels.

Exocrine Function

The adult pancreas produces 10 -20g of pancreatic enzymes in an active form.It secretes a colorless odorless alkaline (pH 7.6-9) juice with enzymes such as – amylase, lipase, proteases and trypsinogen which help digest the fat, protein as well as carbohydrates from the food that we eat. The alkaline juice helps to neutralize the acid secretions of the stomach. It secretes about 1.5 liters of these juices in a day. The stimulants for enzymes secretion are secretin, cholecystokinin and acetylcholine.

The enzymes are conveyed to the upper part of the small intestine called duodenum via a tube called the pancreatic duct.

Endocrine Function

It also secretes two important hormones namely – Insulin and Glucagon which are essential for regulation of glucose in the blood.

  • Insulin is synthesizes by the B cells. Proinsulin is transported from the endoplasmic reticulum to the Golgi complex where it is packaged into granules and cleaved into insulin and residual connective peptide (C peptide).
  • Glycogen is secreted by the A cells of the islet. It elevates blood glucose levels through the stimulation of glycogenolysis and gluconeogenesis. Its major stimulants are aminoacids and cholinergic fibers.
  • Somatostatin is secreted by the D cells of the islet. It inhibits the release of growth hormone and almost all peptide hormones. It also inhibits gastric, pancreatic and biliary secretion.

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