Thursday, June 14, 2012

Islet of Langerhans

Paul Langerhans in 1869 was the first to describe the islets of pancreatic tissue that bear his name.

Human islets of Langerhans are complex micro-organs responsible for maintaining glucose homeostasis. Langerhans are scattered throughout the pancreas, but they are more common in the region of the tail than in the head of the gland.
The human pancreas contains, on average about one million islets, which vary in size from 50 to 300 um wide.

Islets contain five different endocrine cell types, which react to changes in plasma nutrient levels with the release of a carefully balanced mixture of islets hormones into the portal vein.

Insulin originates in the Beta cells, glucagon in the Alpha cells and somatostatin in the Delta cells. The other two pancreatic polypeptide-producing by F cells and ghrelin-producing E or Epsilon cells. Many circulating nutrients regulate the secretion of these hormones.

Insulin dependent (type I diabetes) is caused by a destructive process affecting the insulin-producing B-cells (also called beta-cells) of the islets of Langerhans.

Destruction of B-cells may be induced by immunologic abnormalities, infectious agents, inflammatory tissue damage, and B-cytotoxins such as alloxan and streptozotocin.
Islet of Langerhans
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