The endocrine system regulates many and varied functions of an organism. It is a control system of ductless glands that secrete chemical "instant messengers" called hormones that
circulate within the body via the bloodstream to affect distant cells within specific organs.
Hormones act as "messengers", and are carried by the bloodstream to different cells in the body,
which interpret these messages and act on them. Hormones can change the status, structure of
organs and tissues. Some hormones stimulate the growth of bones, the others can control
metabolism within the cells of the body. There are glands of internal secretion (endocrine
glands) and glands of external secretion (exocrine glands). The former secrete hormones direct
into the bloodstream and the latter into ducts which lead to the exterior of the body.
Pituitary gland, thyroid gland, parathyroid glands, pancreas, adrenal glands, gonads
(ovaries and testes), pineal gland and thymus gland belong to endocrine glands. Mammary,
mucous, salivary, lacrymal and sweat glands belong to exocrine ones.
We'll consider only few of the endocrine glands since the information concerning the rest
of them is to be prepared by the students themselves.
Pancreas is located behind the stomach. It produces hormones in the cells which are called
islets of Langerhans. The hormones of pancreas are insulin and glucagons which regulate the
due metabolism of sugars and starches in the body.
The pineal gland is located in the middle of the brain. This gland secretes melatonin which
affects skin pigmentation (it causes the skin to turn a lighter colour). This gland is thought to
work as a "biological clock" because exposure to light inhibits production of melatonin. Its

function is obscure to some extent as some scientists state it.
The thymus gland is a ductless gland located in the mediastinum behind the sternum and
extends into the neck. It is large in childhood and it shrinks in size in adults. Some scientists
believe that the thymus plays a certain role in the immune process in the body. The exact
function of the gland is also rather uncertain.
The field of medicine that deals with disorders of endocrine glands is endocrinology, a
branch of the wider field of internal medicine.

3. ответьте на вопросы (письменно).
1. What does the endocrine system include?
2. What is the function of the endocrine system?
3. What kinds of gland are there in the human organism?
4. What glands are of internal secretion?
5. What glands belong to the exocrine system?
6. Where is pancreas located?
7. What hormones does pancreas produce and what do they regulate?
8. Where is the pineal gland located and what does it secrete?
9. What is the function of the thymus gland?
10. What field of medicine deals with the disorders of endocrine system?

NikaMalinka2    2   23.10.2020 15:26    18