Human Biochemistry Volume 2 - Murray R. 1993

Biochemistry of Intra- and Intercellular Communication
Pancreatic Hormones
Introduction

The Pancreas is, in effect, two distinct Organs combined into a single morphological Structure. Its acinar component performs an exocrine function by secreting Enzymes and ions into the lumen of the duodenum, which are essential for digestive processes. The Endocrine portion of the gland consists of 1–2 million islets of Langerhans, which account for 1–2% of the total pancreatic mass. The islets are composed of several Cell types (Table 51.1).

The islet apparatus of The pancreas secretes at least four Hormones: Insulin, Glucagon, Somatostatin, and Pancreatic Polypeptide. These hormones are released into the pancreatic vein, which drains into the portal vein—a feature of great significance, as the Liver serves as the primary target for both insulin and glucagon. The main role of these two hormones is to regulate Carbohydrate METABOLISM, though they also influence numerous other processes. Somatostatin was first identified in the Hypothalamus as a hormone that inhibits Growth Hormone secretion; however, its concentration in the pancreas is higher than in the hypothalamus. This hormone is involved in the local Regulation of Insulin and glucagon secretion. Pancreatic polypeptide influences gastrointestinal secretion.

Class="center">Table 51.1. Cell types in the islets of Langerhans