The Endocrine Glands

All glands in the human body can be divided into glands with ducts and ductless. Ductless glands have no duct but they make a secretion which they pour into the blood stream. These secretions are called internal secretions or hormones, and glands which produce them are also called endocrine glands.

The chief ductless glands are: the thyroid gland, the adrenal glands and the pituitary gland.

There are also other important glands which produce internal secretions as well as other substances, e.g. the pancreas, the liver and the reproductive glands.

The thyroid gland lies in the front of the neck. It consists of two lobes lying on either side, joined by a narrow band which crosses the trachea immediately below the larynx. The gland is well supplied with blood vessels and consists essentially of secreting cells. The cells secrete thyroxin, which passes into the circulation. Thyroxin controls the general metabolism or activity of the body tissues.

The adrenal glands are two small triangular glands lying one over each kidney. They consist of two parts, cortex and medulla. The outer part produces a secretion which affects sex. Oversecretion produces masculinity in the female and in the male it produces too early development of the male reproductive organs.

The medulla produces a very important secretion called adrenalin, It secreted amount increases in excitement and strong emotions such as fear or anger. The adrenals are therefore sometimes called the glands of “flight and fight”.

The pituitary gland (hypophysis) is a small gland about the size of a pea and yet is of great importance. It lies in the pituitary fossa in the base of the skull. It consists of an anterior and a posterior lobe.

The anterior lobe is the larger and produces a number of important hormones affecting growth and sexual development and the functioning of the ductless glands, particularly the thyroid and the adrenal glands. Undersecretion of this lobe in childhood causes dwarfing. Oversecretion causes overgrowth or gigantism. In the adult this oversecretion causes overgrowth of the head, hands, and feet, particularly affecting the lower jaw. This condition is known as acromegaly.

The posterior lobe produces the secretion known as pituitrin. This stimulates involuntary muscle and therefore contracts the blood vessels and raises blood pressure, stimulates peristalsis, contracts the uterus; it affects the use of water by the body.

Exercise 6. Answer the questions:

1. How are glands in the human body classified?

2. What is hormone?

3. What are the main ductless glands?

4. What is the structure of the thyroid gland?

5. What does thyroxin control?

6. What is the structure of the adrenal glands?

7. When is adrenalin secreted?

8. What is the structure of the pituitary gland?

9. What does the pituitary gland affect?

Exercise 7. I. Form new words with the prefix OVER meaning “понад, вверх”. Translate them:

Model: over+ dosage →overdosage (передозування)

weight, cooling, heating, work, salt, sensitive, sleep, use, talkative, curious, load, excitement, dose, estimate, eating, growth, development, action.

Date: 2015-12-12; view: 630; Нарушение авторских прав