Endocrine glands

Endocrine glands, or glands of internal secretion, are glands without excretory ducts. They produce special substances called hormones, which are secreted directly into the blood. The hormones are carried throughout the organism with the blood and are delivered to various organs whose activity they either stimulate or depress.

Hormones play a very important part in the organism. Many of them affect metabolism and the functioning of the cardiovascular, reproductive, and other systems. A disturbance in the activity of the endocrine glands is accompanied by changes throughout the organism. These changes may be due to an increase in the function of a gland (hyperfunction) or a decrease (hypofunction).

The chemical composition of some hormones is well-known. Various hormonal preparations are made synthetically or from the corresponding glands of animals (endocrine preparations) and are widely used in medicine. It should be noted that hormones are substances with very high biological activity.

The endocrine glands include the hypophysis (or pituitary), the epiphysis cerebri (or pineal), the thyroid, the parathyroids, the thymus, the islet part of the pancreas, the adrenals and the incretory part of the sex glands, Each gland consists of glandular epithelial tissue and has an extensive network of blood vessels and a large number of nerve fibres (from the vegetative nervous system)

The functions of all endocrine glands are interconnected, and the glands make up a single system. The hypophysis is the chief gland of this system: it produces special substances which stimulate the activities of the other endocrine glands.

The influence of various substances (mainly hormone) acting on the organism through the blood is called humoral regulation.

The activities of endocrine glands are regulated by the nervous system. The nervous system exercises direct control over the endocrine glands through the nervous and neurohumoral control, particularly through the hypophysis. The hormones in their turn affect the functions of the different parts of the nervous system.

POST-TEXT ASSIGMENTS

Exercise 5. Answer the questions to the text:

1. What is the other name for endocrine glands?

2. Where are the hormones secreted?

3. What is the role of hormones?

4. How are the hormones made?

5. What are the parts of the endocrine system?

6. What is humoral regulation?

7. What is the chief gland of the endocrine system?

8. What are the activities of the endocrine glands regulated by?

Exercise 6. Match the terms with their definitions:

1. humoral regulation     2. hypophysis     3. thymus     4. adrenal gland     5. parathyroid

a) triangle-shaped glands located on top of the kidneys b) A gland that regulates calcium, located behind the thyroid gland in the neck. c) a small, somewhat cherry-shaped double-lobed structure attached to the base of the brain, constituting the master endocrine gland affecting all hormonal functions of the body d) pyramid-shaped lymphoid organ that, in humans, is immediately beneath the breastbone at the level of the heart. e) the coordination of physiological and biochemical processes effected through the body’s fluids by means of biologically active substances (metabolites, hormones) released by cells, organs, and tissues in the course of their vital activities.

Дата добавления: 2015-10-21