MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

SECTION 3. ANATOMICAL AND PHYSIOLOGICAL ASPECTS OF THE SELF-REGULATION OF BODY FUNCTIONS

ENDOCRINE GLANDS AND THEIR PATHOLOGY

ENDOCRINE PART OF THE PANCREAS

1. PANCREATIC HORMONES

The Pancreas was described in detail in the section on "Splanchnology". The Endocrine Part—pancreatic islets (islets of Langerhans)—is located primarily in the tail region of the gland.

Beta Cells (70%) of the pancreatic islets of Langerhans synthesize the hormone Insulin; alpha cells (20%) synthesize Glucagon; delta cells (10%) synthesize Somatostatin.

Insulin regulates carbohydrate, protein, and Lipid METABOLISM. By increasing the permeability of Cell membranes (except for Brain cells) to glucose, it lowers Blood glucose levels. Insulin also stimulates Glycogen synthesis in The Liver and Muscles and reduces The formation of glucose from Amino Acids.

In the Regulation of Protein metabolism, insulin acts as an anabolic hormone: it stimulates Protein Synthesis from Amino Acids and their Transport from the blood into The Cell. In regulating lipid metabolism, insulin enhances the formation of Fatty acids from Carbohydrate Metabolism products and the accumulation of fat reserves.

Glucagon is an antagonist of insulin; it increases blood glucose levels.

The regulation of pancreatic hormone secretion depends on blood glucose levels. When glucose rises (hyperglycemia), insulin secretion increases; when glucose concentration drops (hypoglycemia), insulin release into the blood decreases. Blood glucose levels depend on its interaction with glucose receptors located in the Blood Vessels, pancreas, and Hypothalamus. Stimulation of parasympathetic nerves increases insulin secretion, which may lead to hypoglycemia. Activation of the sympathetic Nervous system leads to hyperglycemia.

The normal blood glucose concentration is 3.33-5.55 mmol/L. At this concentration, glucose is not filtered by the Kidneys, and sugar is absent in the urine.

Insulin deficiency of the pancreatic islet apparatus results in a severe condition known as Diabetes Mellitus.