structure and function of the pancreas

Question 1

function of the pancreas

Answer 1

The pancreas has two main functions in the body, as an:
• exocrine gland - to produce enzymes and release them via a duct into the duodenum
• endocrine gland - to produce hormones and release them into the blood.

Question 2

role as an exocrine gland

Answer 2

Most of the pancreas is made up of exocrine glandular tissue.
This tissue is responsible for producing digestive enzymes and an alkaline fluid known as pancreatic juice. The enzymes and juice are secreted into ducts which eventually lead to the pancreatic duct. From here they are released into the duodenum, the top part of
tail
pancreatic duct
the small intestine. The pancreas produces three important types of digestive enzymes:
• Amylases - break down starch into simple sugars. For example, pancreatic amylase.
• Proteases - break down proteins into amino acids. For example, trypsin.
• Lipases - break down lipids into fatty acids and glycerol. For example, pancreatic lipase.

Question 3

role as an endocrine gland

Answer 3

The pancreas is responsible for producing insulin and glucagon. These two hormones play an essential role in controlling blood glucose concentration, which you will read about in Topic 14.3, Regulation of blood glucose concentration. Within the exocrine tissue there are small regions of endocrine tissue called islets of Langerhans. The cells of the islets of Langerhans are responsible for producing insulin and glucagon, and secreting these hormones directly into the bloodstream.

Question 4

histology of the pancreas

Answer 4

Islets of langerhans, lightly stained, large spherical clusters, endocrine pancreas, produce and secrete hormones

pancreatic acini, darker stained, small berry-like clusters, exocrine pancreas, produce and secrete digestive enzymes

Question 5

islets of langerhans

Answer 5

Within the islets of Langerhans are different types of cell. They are classified according to the hormone they secrete:
• a (alpha) cells - these produce and secrete glucagon
• B (beta) cells - these produce and secrete insulin

Alpha cells are larger and more numerous than beta cells within an islet.
Using standard staining techniques, it is often very difficult to distinguish between the cell types within an islet of Langerhans. In Figure 2, a differential stain has been used. The ß cells of the islets that produce insulin are stained blue, and the a cells that produce glucagon are stained pink.

Light micrograph of a section through the pancreas. The islet of Langerhans (centre right) is composed of groups of secretory cells. The main secretions from these cells are the hormones insulin and glucagon, which control blood sugar. These cells are endocrine - their secretions go straight into the bloodstream. The cells surrounding the islet are packed into secretory acini (pink) which secrete digestive enzymes. This part of the pancreas is exocrine - the enzymes pass straight out into the gut, via ducts. The structure on the left is a branch of the pancreatic duct, × 195 magnification