Endocrine glands and the most important pituitary glands in the human body
Hormones in the human body
Hormone is a chemical substance ( or a chemical message ) that controls and organizes most of the vital activities and functions in the bodies of living organisms , Hormones are secreted in the body by some organs called Endocrine glands or Ductless glands .
The nervous system organizes and coordinates both the activities and functions of the organs of living organisms but scientists through their experiments and researches proved that there is another form of organizing and coordinating these activities and functions .
This form is performed by the chemical substances secreted by the special cells in the body , these secretions , known as Hormones , The hormone is any member of a class of signaling molecules produced by the glands in multi-cellular organisms .
The endocrine glands are the ductless glands that secrete their hormones directly in the blood , They secrete more than 50 hormones in the human body , The cells ( which are known as target cells ) that the hormones affect are almost located away from the endocrine gland that secretes the hormone .
So , The blood is the only way for this hormone to reach its site of action ( target cells ) , Endocrine glands are called by this name because they secrete their hormones directly in the blood without passing through the ducts .
The endocrine glands secrete the hormones in limited quantities , If one of the glands does not act properly , the balance of action of these glands gets disturbed and man has a state of a hormone disorder .
The most important endocrine glands in the human body
The glands are located throughout various parts of the human body , These glands take on the critical task of releasing hormones , There are many important glands in the human body such as Pituitary gland , Thyroid gland , Adrenal glands , Pancreas , Two tests , And two ovaries .
The ability of the target cell [ disambiguation needed ] to respond to the hormone depends on the receptors presence within the cell or on its plasma membrane , to which the hormone can bind .
The hormone receptors are the dynamic structures , Changes in number and sensitivity of the hormone receptors may occur in response to high or low levels of the stimulating hormones .
Blood levels of hormones reflect the balance between the secretion and the degradation/excretion , The liver and the kidneys are the main organs which degrade the hormones , breakdown the products are excreted in the urine and the feces , Hormone half-life and duration of activity are limited and vary from hormone to hormone .
The pituitary gland
It is located below the brain , It is a small gland in the size of a pea seed , It consists of two lobes , It secretes the hormones that regulate the activities of other endocrine glands , It is known as the master gland or the main gland .
Pituitary gland secretes a group of hormones , The hormones of the pituitary gland are Growth hormone , Facilitating hormone during delivery , Regulating water hormone in the body , Adrenal glands activating hormone , Thyroid stimulating hormone ( TSH ) .
Pituitary gland secretes also Mammary glands activating hormone to secrete the milk , And Sexual glands activating hormone ( two tests and two ovaries ) that regulates the growth and the development of sex organs .
Growth hormone controls the speed of growth rate of body muscles , bones and other organs , It determines the height that the person will reach when he becomes a fully grown .
Some diseases resulted from the growth hormone disorder in the human body
The growth hormone disorder causes Dwarfism , where the body stops growing , so , the person becomes a dwarf , Dwarfism is due to the decrease in secretion of the growth hormone at the childhood .
The growth hormone disorder causes Gigantism , Gigantism causes a continuous growth in the limbs’ bones , so , the person becomes a giant , Gigantism is due to the increase in secretion of the growth hormone at the childhood .
If the secretion of the growth hormone is decreased in the childhood , The body stops growing , So , the person becomes a dwarf , If the secretion of the growth hormone is increased in the childhood , A continuous growth in the bones of the limb will take place , So , The human being will be a giant .