Lesson 5

Date: 2015-10-07; view: 433.

The Endocrine System

Unit 2

· Match the following English words and expressions with their Ukrainian equivalents:

1. adrenal a. паращитоподібна залоза

2. gonad b. яєчник

3. pituitary c.шишкоподібна залоза

4. ovary d. підгрудинна, вилочкова залоза

5. thyroid e. щитоподібна залоза

6. hypothalamus f. наднирник

7. thymus g. гонада

8. parathyroid h. гіпофіз

9. pineal i. гіпоталамус

THE ENDOCRINE SYSTEM

The endocrine system is one of the body's main systems for communicating, controlling and coordinating the body's work. It is instrumental in regulating mood, growth and development, tissue function, and metabolism, as well as sexual function and reproductive processes.

In general, the endocrine system is in charge of body processes that happen slowly, such as cell growth. Faster processes like breathing and body movement are controlled by the nervous system.

The nervous system sends electrical messages to control and coordinate the body. The endocrine system has a similar job, but uses chemicals to “communicate”. These chemicals are known as hormones. A hormone is a specific messenger molecule synthesized and secreted by a group of specialized cells called an endocrine gland. These glands are ductless, which means that their secretions (hormones) are released directly into the bloodstream and travel to elsewhere in the body to target organs.

The major glands that make up the human endocrine system are: the hypothalamus, pituitary, thyroid, parathyroids, thymus, adrenals, pineal body, and the reproductive glands, which include the ovaries and testes. The pancreas is also part of the system, even though it is also associated with the digestive system because it also produces and secretes digestive enzymes.

Although the endocrine glands are the body's main hormone producers, some non-endocrine organs — such as the brain, heart, lungs, kidneys, liver, thymus, skin, and placenta — also produce and release hormones.

The hypothalamus, a collection of specialized cells that is located in the lower central part of the brain, is the primary link between the endocrine and nervous systems.

Although it is no bigger than a pea, the pituitary gland, located at the base of the brain just beneath the hypothalamus, is considered the most important part of the endocrine system. It's often called the "master gland" because it makes hormones that control several other endocrine glands.

The production and secretion of pituitary hormones can be influenced by factors such as emotions and seasonal changes. To accomplish this, the hypothalamus relays information sensed by the brain (such as environmental temperature, light exposure patterns, and feelings) to the pituitary.

The thyroid, located in the front part of the lower neck, is shaped like a bow tie or butterfly and produces the thyroid hormones. These hormones control the rate at which cells burn fuels from food to produce energy. As the level of thyroid hormones increases in the bloodstream, so does the speed at which chemical reactions occur in the body.

Thyroid hormones also play a key role in bone growth and the development of the brain and nervous system in children. The production and release of thyroid hormones is controlled by thyrotropin, which is secreted by the pituitary gland.

Attached to the thyroid are four tiny glands that function together called the parathyroids. They release parathyroid hormone, which regulates the level of calcium in the blood with the help of calcitonin, which is produced in the thyroid.

The body has two triangular adrenal glands, one on top of each kidney. The adrenal glands have two parts, each of which produces a set of hormones and has a different function. The outer part, the adrenal cortex, produces hormones called corticosteroids that influence or regulate salt and water balance in the body, the body's response to stress, metabolism, the immune system, and sexual development and function.

The pineal body, also called the pineal gland, is located in the middle of the brain. It secretes melatonin, a hormone that may help regulate the wake-sleep cycle.

The gonads are the main source of sex hormones. In males, they are located in the scrotum. Male gonads, or testes, secrete hormones called androgens, the most important of which is testosterone. These hormones regulate body changes associated with sexual development.

The female gonads, the ovaries, are located in the pelvis. They produce eggs and secrete the female hormones estrogen and progesterone.

The pancreas produces (in addition to others) two important hormones, insulin and glucagon. They work together to maintain a steady level of glucose, or sugar, in the blood and to keep the body supplied with fuel to produce and maintain stores of energy.

Once a hormone is secreted, it travels from the endocrine gland through the bloodstream to target cells designed to receive its message. When the hormone reaches its target cell, it locks onto the cell's specific receptors and these hormone-receptor combinations transmit chemical instructions to the inner workings of the cell.

When hormone levels reach a certain normal or necessary amount, further secretion is controlled by important body mechanisms to maintain that level of hormone in the blood. This regulation of hormone secretion may involve the hormone itself or another substance in the blood related to the hormone.

· Name six of the better known endocrine glands:

1. _________

2. _________

3. _________

4. _________

5. _________

6. _________

· Sign the organs of the endocrine system (the endocrine glands) on the picture given below:

· Choose the best variant to finish the test:

1. Glands are small organs located throughout your body that secrete substances called:

a. plazma

b. hormones

c. enzymes

d. bile

2. Hormones help your body by:

a. telling cells what to do

b. helping you breathe

c. sending nerve messages

d. oxidizing your blood

3. Which of the following is not a part of the endocrine system:

a. thyroid

b. adrenals

c. appendix

d. pituitary

4. Where are the major endocrine glands located:

a. in the head, shoulders, knees and toes

b. in the brain, joints, abdomen and spinal column

c. in the brain, neck, abdomen and groin

d. in the gallbladder, appendix, tonsils and spleen

5. This gland is sometimes called a master gland, though it is only about the size of a pea:

a. pituitary

b. adrenal

c. pineal

d. hypothalamus

6. What is the largest endocrine gland:

a. adrenal

b. thymus

c. pituitary

d. pancreas

7. This is a common problem with the endocrine system:

a. hemophilia

b. diabetes

c. lung cancer

d. bad gas

8. What hormone does the pancreas make:

a. insulin

b. adrenaline

c. growth hormone

d. sugar

9. Where can you find the pituitary gland:

a. in your left foot

b. next to your liver

c. at the base of the brain

d. near your heart and lungs

10. Which gland makes hormones that help you grow and stay full of energy:

a. thyroid

b. adrenal

c. muscle

d. pituitary

· Match two columns to give the correct explanations of each term:

1. pituitary

2. thymus

3. adrenal

4. ovary

5. thyroid

6. pancreas

a. a lymphoid organ situated in the neck that produces T cells for the immune system. It becomes much smaller at the approach of puberty.

b. a female reproductive organ in which ova or eggs are produced.

c. the major endocrine gland. A pea-sized body attached to the base of the brain, it is important in controlling growth and development and the functioning of the other endocrine glands.

d. a large gland behind the stomach that secretes digestive enzymes into the duodenum.

e. a pair of ductless glands situated above the kidneys.

f. a large ductless gland in the neck that secretes hormones regulating growth and development through the rate of metabolism.

· Fill in the gaps in the extract using the given words:

larynx, cranial, anterior, thyroxin, ductless, brain, endocrine, pea, trachea, internal, pea, posterior, neck, lobes, thyroid.

Endocrine glands are glands of _______ secretion. These glands are also called _______ glands as they don't have any ducts. Hormones are the secretions produced by _______ glands. The pituitary body is a small______-sized and _______-shaped structure. It is attached to the base of the _______ in the region of the hypothalamus. In addition, it is housed within a hollow of the bony floor of the ________ cavity. The pituitary body is actually two glands: the ______ pituitary gland and the ________ pituitary gland.

The thyroid gland is in the _______ region just below the _______ and surrounds the _______. The masses on either side of the trachea are the right and left thyroid _______. Each lobe of the thyroid gland is supplied by the superior and inferior _______ arteries. The primary hormone of the thyroid gland is _______.