The pancreas was first identified for western civilization by Herophilus (335–280 BC), a Greek anatomist and surgeon. Only a few hundred years later, Rufus of Ephesus, another Greek anatomist, gave the pancreas its name. The pancreas secrets three different peptide hormones. They are Insulin, Glucagon and Stomatostatin.
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Anatomy of Pancreas:
- The pancreas (from pankreas: panG=all, kreasG=flesh); effering to the fleshy nature of the tissue) is both exocrine & endocrine gland.
- It locates the below the stomach between the curve of duodenum & spleen.
- It is a compact & lobulated organ.
- The pancreas composed of two types of cell.
- The pancreas secretes peptide hormones.
- Pancreatic hormones are peptide hormones
1. Glandular cells (or) Acinar (or) Acinii (exocrine):
The cells make up the bulk of the pancreatic tissues & secrete digestive juices into the duodenum by the pancreatic duct.
2. Polygonal cells (or) islets of langerhans (or) islet tissue (endocrine):
Its secretion releases into the blood directly. These were discovered by “Langerhans” in 1867. The islets of Langerhans in mammals contain three major types of cells, they are a-cells, b-cells, g-cells.
- alpha-cells –> Secretes – “Glucagon” hormones
- beta-cells –> Secretes – “Insulin” hormones
- gamma-cells –> Secretes-“Somatostatin” hormone
The pancreas secretes three different hormones, namely,
Peptide Hormone – Glucagon:
Chemistry of Glucagon:
- First isolated in crystalline form by “Benhrens”& other.
- This peptide hormone has a molecular weight of 3,485 and PI-8 and it has 29 amino acid residues.
- “His” is the N-terminal amino acid and “Thr”, the C-terminal amino acid.
- It contains no Cys, Pro, Ile, but Meth & Try are present in appreciable amounts.
Mechanism of Action:
Secretion of Glucagon:
Functions of Peptide hormone – Glucagon:
- Glucagon stimulates glycogenolysis.
- Glucagon acts through cAMP as its second messenger.
- Glucagon stimulates gluconeogenesis by activation of pyruvate carboxylase.
- Glucagon inhibits glucose oxidation by inhibiting pyruvate kinase.
- It increases potassium release from liver.
- In adipose tissue as well as in liver it increases the breakdown of lipids to fatty acids and glycerol.