Endocrine System:
Definition:
The endocrine system is a control system of the body, which controls various functions of the human body through secretions known as hormones, secreted by the endocrine glands.
Endocrine Glands:
Endocrine glands are secretary tissues (glands) which secrete hormones directly into the blood stream. They are also called ductless glands. The study of endocrine glands is called endocrinology.
Important Endocrine Glands & Their Functions (secretions)
Following are the important endocrine glands of the human body.
i) Pituitary Gland
ii) Hypothalamus
iii) Thymus
iv) Pineal
v) Thyroid
vi) Parathyroid
vii) Adrenal
viii) Pancreas
ix) Testes
x) Ovaries
Pituitary Gland:
The pituitary gland is a small bean-shaped reddish gray organ, located near the hypothalamus (forebrain). It produces at least nine hormones which perform following functions:
Functions:
– Responsible for normal skeletal growth, milk secretion in mammary glands.
– Controls normal functioning of thyroid and adrenal glands
– Stimulates the formation of the graffian follicles in the female ovary and development of spermatozoa in male.
– Stimulate the contraction of the uterine muscles during the final stage of pregnancy
– Control the amount of urine secreted by the kidney.
Hypothalamus
The hypothalamus is located immediately below the thalamus at the centre of the brain, and controls many automatic functions of the body.
Function:
The general functions of the hypothalamus are of extreme importance for the body, such as:
– Pituitary gland regulation
– Blood pressure regulation
– Hunger and salt cravings
– Feeding reflexes
– Thirst
– Body temperature regulation
Thymus:
The thymus gland, which is shaped like a pyramid, is a specialized organ of the human immune system. It is also one of the important glands in the human body. It is a pinkish gray colored organ that is situated in the upper thoracic region, under the sternum or the breast bone.
Function:
The thymus gland is very active, when the individual is a child. It plays a crucial role in developing and improving a child’s immunity system. The main function of the thymus gland is to produce and process lymphocytes or T cells.
Pineal Gland:
The pineal gland is a pine cone shaped gland of the endocrine system. A structure of the diencephalon of the brain, the pineal gland produces several important hormones including melatonin.
Function:
The pineal gland is involved in several functions of the body including:
• Secretion of the Hormone Melatonin
• Regulation of Endocrine Functions
• Conversion of Nervous System Signals to Endocrine Signals
• Causes Feeling of Sleepiness
• Influences Sexual Development
Thyroid Gland:
The thyroid gland is paired organ located in upper region of the neck in front of windpipe. It produces the hormone thyroxin (T4), Triiodothyronine (T3) and calcitonin.
Functions:
– Plays an important role in regulating the body’s metabolism
– The T4 and T3 hormones stimulate every tissue in the body to produce proteins and increase the amount of oxygen used by cells.
– The calcitonin hormone works together with the parathyroid hormone to regulate calcium levels in the body.
Parathyroid Gland:
The parathyroid glands are embedded in the thyroid gland.
Functions:
– Controls the concentration of calcium (Ca ion) and phosphorus (phosphate) in the blood.
– Stimulates the absorption of calcium and magnesium from the gut.
– Increases tubular reabsorption of calcium, magnesium and hydrogen ions.
Pancreas:
The pancreas is located deep in the abdomen, sandwiched between the stomach and the spine. It produces two important hormones which are insulin and glucagon.
Functions:
– Insulin and glucagon are especially important for the maintenance of blood sugar, as insulin lowers the blood sugar and glucagon increases the blood sugar according to the body’s needs.
Adrenal Gland:
The adrenal gland curve over the top of each kidney in abdomen. The important hormones secreted by adrenal gland are adrenaline, Aldosterone hormone, and cortisol.
Function:
– Adrenal glands are responsible for secreting hormones essential for carrying out some important metabolic processes. Besides, they also help the body in dealing with physical and mental stress.
Ovaries:
It is not only a reproductive organ which produces gametes but also make many steroidal hormones. The important ovary hormone is estrogen.
Function:
– Ovary hormones are responsible for female characteristics e.g. sound, body, bones, hair etc.
Testes:
It is not only a reproductive organ in males but also performs endocrine functions. Important hormone of testes is androgens.
Function:
Testes hormones are responsible for the development of male characteristics in male e.g. sound, bones, hairy body etc.
Some Important Hormone Of Endocrine Glands:
i) Insulin: By Pancreas
ii) Thyroxin: By Thyroid Gland
iii) Adrenalin: By Adrenal Gland
iv) Oestrogen: Ovaries
v) Testosterone: Testes
vi) Cortisol: Adrenal Gland
vii) Melatonin: Pineal Gland
viii) Glucagon: Pancreas
ix) Aldosterone: Adrenal Gland
x) Renin: Adrenal Gland
Exocrine Glands:
Exocrine glands are the glands which do not pour their secretions directly into blood (like endocrine glands) but into a duct. These are the glands with ducts and the effect of their secretions is not generalized on all tissues of the body but specialized.
Example:
i) Salivary Glands
ii) Exocrine Pancreas
iii) Lacrimal Gland
iv) Bile Producing Cells of Liver
v) Secretory Cells of Stomach and Intestine
Exocrine Pancreas:
Pancreas secret pancreatic juice which contains a large number of digestive enzymes. Pancreatic juice goes to the intestine thorough a pancreatic duct and performs the function of digestion inside the intestine.
Mammary Glands:
Mammary glands are also exocrine glands which secret milk or colostrum. Milk is collected by a series of ducts and secreted outside the body.
Salivary Glands:
Salivary glands are present inside the jaw. These secret saliva which comes to the mouth (oral cavity) through salivary duct. Saliva is responsible for lubrication of food and early digestion of starch.
Lacrimal Gland:
Lacrimal is the gland which is present in the eye. Its secretion is the lachrymal secretion in the form of tears. Lachrymal secretion washes the eye and the lysozyme enzyme present in this secretion kill bacteria to protect eye.
Bile Producing Cells Of Liver:
The liver produces bile then it is stored in the gall bladder until need to digest fatty foods.
Secretory Cells Of Stomach And Intestine:
Secretory cells of stomach secrete gastric juice which is poured into the stomach. Gastric juice contains enzyme like pepsin which digest proteins. Similarly secretory cells of intestine secrete intestinal juice which contains many digestive enzymes
Exocrine Glands And Their Secretions:
i) Lachrymal Gland: Tears
ii) Sweat Gland: Sweat
iii) Salivary Gland: Saliva
iv) Mammary Glands: Milk
v) Liver: Bile
vi) Sebaceous Gland: Sebum
Hormones:
Hormones are the chemical substances secreted by the endocrine glands. They carry electro-chemical messages to different parts of the body. Hormones are circulated in the body through blood. The function of endocrine system depends upon these hormones. These hormones work in the similar way as the nervous system works in the body. Insulin, glucagon, thyroxin and testosterone are few kinds of hormones. Hormones play an important role in a living organism. A small amount of hormones in the blood produces specific effects in the body. Several dozen hormones travel through the blood stream and influence different kinds of target cells, modifying their activity in a variety of ways.
Antibody:
Antibody is a protein produced by white blood cells that help to destroy bacteria.
Antibodies react with the antigens and inactivate or destroy them.
A large number of antibodies are produced in blood which are targeted against various types of antigens.
Antigens are foreign molecules, cells, bacteria, viruses or fungi which enter the body usually a disease causing microorganisms.
Antibodies are the integral part of the defence mechanism of human body.
They are also involved in immunity against disease.
Haemophilia:
It is a disease in which the person has prolonged blood clotting time resulting in excessive bleeding from injury.
It is due to the deficiency of vitamin K.
It is a semi lethal disease controlled by recessive gene.
It is less common in women than in men.
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