The most important endocrine glands are:
• Pituitary gland;
• thyroid;
• parathyroid glands;
• endocrine part of the pancreas;
• the adrenal glands;
• Sex glands (ovaries in women and testicles in men).
The role of hormones
The function of the endocrine glands lies in the release of hormones directly into the bloodstream. Different hormones can belong to different groups of chemicals. They migrate with a current of blood, regulating the activity of target organs. Membranes of cells of these organs have receptors sensitive to a certain hormone. For example, one of the hormones causes sensitive cells to produce a signal substance - cyclic adenosine monophosphate (cAMP), which affects the processes of protein synthesis, storage and storage of energy, as well as the production of some other hormones. Each of the endocrine glands produces hormones that perform certain functions in the body.
• Thyroid
Responses mainly for the regulation of energy metabolism, producing hormones thyroxine and triiodothyronine.
• Parathyroid glands
They produce parathyroid hormone, which is involved in the regulation of calcium metabolism.
• Pancreas
The main function of the pancreas is the production of digestive enzymes. In addition, it synthesizes hormones insulin and glucagon.
• Adrenal glands
The outer layer of the adrenals is called the cortex. It produces corticosteroid hormones, including aldosterone (involved in the regulation of water-salt metabolism) and hydrocortisone (involved in the processes of growth and tissue repair). In addition, the cortex produces male and female sex hormones (androgens and estrogens). The internal part of the adrenal gland, or brain substance, is responsible for the production of adrenaline and norepinephrine. The joint action of these two hormones contributes to the increase in heart rate, increase in blood glucose level and blood flow to the muscles. Excess or lack of hormones can lead to serious diseases, developmental anomalies or death. Total control over the production of hormones (their number and rhythm of excretion) by the brain system.
Pituitary
A pituitary gland is a pea-sized gland located at the base of the brain and producing more than 20 hormones. These hormones serve to regulate the secretory activity of most other endocrine glands. The pituitary gland has two lobes. The anterior part (adenohypophysis) produces hormones that regulate the function of other endocrine glands.
The most important hormones of the pituitary gland are:
• thyroid-stimulating hormone (TTG) - stimulates the production of thyroxine by the thyroid gland;
• adrenocorticotropic hormone (ACTH) - increases the production of hormones by the adrenal glands;
• follicle-stimulating hormone (FSH) and luteinizing hormone (LH) - stimulate the activity of the ovaries and testes;
• Growth hormone (HHG).
Posterior lobe of the pituitary gland
The posterior part of the pituitary (neurohypophysis) is responsible for the accumulation and release of hormones produced in the hypothalamus:
• vasopressin, or antidiuretic hormone (ADH), - controls the volume of produced urine, thus participating in maintaining the water-salt balance;
• oxytocin - affects the smooth muscles of the uterus and the activity of the mammary glands, participating in the process of delivery and lactation.
The mechanism, called the feedback system, allows the pituitary to determine when it is necessary to isolate the hormones that stimulate the corresponding glands. An example of self-regulation due to feedback is the effect of pituitary hormones on the secretion of thyroxin. Increased thyroxine production by the thyroid gland leads to suppression of pituitary thyroid-stimulating hormone (TSH) production. The function of TSH is to increase the production of thyroxine by the thyroid gland. The decrease in the level of TSH leads to a decrease in the production of thyroxine. As soon as its secretion falls in the pituitary gland it responds by increasing the production of TSH, which contributes to the constant maintenance of the necessary level of thyroxine in the body. The feedback system operates under the control of the hypothalamus, which receives information from the endocrine and nervous systems. Based on this information, the hypothalamus secretes regulatory peptides, which then enter the pituitary gland.