Pancreas

Pancreas - Introduction

Pancreas - Gross Structure of Pancreas

• The pancreas is about 6 inches long and is a pale grey gland which consists of a broad head, a body and a narrow tail.
• It sits across the back of the abdomen, behind the stomach. 
• The head of the pancreas is on the right side of the abdomen and is connected to the curve of the duodenum (the first section of the small intestine), through a small tube called the pancreatic duct. 
• The narrow end of the pancreas, called the tail, extends to the left side of the body.
• It is surrounded by other organs, including the stomach, spleen, liver and small intestine.
• The pancreas plays an important role in digestion and in regulating blood sugar, as it makes "enzymes to digest proteins, fats, and carbs in the intestines" and produces the hormones insulin and glucagon.

Pancreas - Histological Structure of Pancreas

Pancreas - Histological Structure of Pancreas

• Pancreas is both an exocrine and endocrine gland. 
• The exocrine part is classified as a lobulated gland because it consists of a large number of lobules made up of approximately one million ‘berry-like’ clusters of small cells called acini, connected by short intercalated ducts. 
• The walls of these lobules consists of secretory cells which produces digestive enzyme precursors.
• Each lobule is drained by a tiny duct and these unite with those draining adjacent lobules and drain into a network of collecting ducts eventually to form the pancreatic duct. 
• The pancreatic duct then runs the length of the pancreas and unites with the common bile duct, to form the hepato pancreatic duct and opens into the duodenum at its midpoint. 
• Exocrine part of the pancreas secretes pancreatic juice so it's functions are concerned with digestion.
• The components of the pancreatic juice are:
• Bicarbonate.
• Carbohydrate digesting enzymes (pancreatic amylase).
• Pancreatic lipase.
• Nucleases.
• Inactive form of protein digesting enzymes (trypsinogen and chymotrypsinogen) and pancreatic carboxypeptidases.
• These inactive enzymes are converted to active enzymes (trypsin and chymotrypsin) upon secretion into the lumen of the duodenum (by enterokinase of intestinal juice).
• The endocrine pancreas refers to those cells within the pancreas that synthesize and secrete hormones.
• The endocrine pancreas consists of a variety of neuroendocrine cell types that are interspersed in small clusters known as islets within the structure of the exocrine pancreas.
• This group of specialized cells is known as islets of Langerhans.
• Humans have roughly around one million islets.
• They do not have ducts.
• Functions of Islets of Langerhans, the endocrine part, consists primarily of the secretion of the two major hormones, glucagon and insulin which are involved in glucose homeostasis.
• Four cell types have been identified in the islets, each producing a different hormone with specific actions:
• A cells or alpha cells produce glucagon.
• B cells or beta cells produce insulin.
• D cells or delta cells produce somatostatin.
• F or D1 cells produce pancreatic polypeptide.
• Both insulin and glucagon are important in the regulation of carbohydrate, protein and lipid metabolism:
• Insulin is an anabolic hormone, that is, it increases the storage of glucose, fatty acids and amino acids in cells and tissues.
• Glucagon is a catabolic hormone, that is, it mobilizes glucose, fatty acids and amino acids from stores into the blood.