Other Endocrine Glands

Other endocrine glands

Hormones are also produced in several other organs of the body that are not usually considered endocrine glands. These organs include the small intestine, which secretes secretin, which causes the secretion of pancreatic juice, and the hormone cholecystokinin, which stimulates contraction of the gallbladder. The stomach, liver and kidneys, according to some researchers, also have endocrine functions, but the evidence in favor of this is not yet entirely convincing.

The thymus gland (otherwise the thymus gland, or thymus) is a fairly large gland that exists only in childhood, lies in the upper part of the chest cavity, covering the upper end of the trachea. In its histological structure, it is similar to lymphatic tissue and produces lymphocytes - one of the types of white blood cells. This gland is large in size in the early period of life, and after puberty it regresses; in this regard, attempts were made to show that it secretes a hormone that delays the onset of puberty, but clear data in favor of this point of view was not obtained.

The pineal gland (or pineal gland) is a small round formation lying above the thalamus, between the cerebral hemispheres; It has long been suggested that the pineal gland has endocrine activity; such assumptions are explained mainly by the fact that no other function is known for it. It has been suggested that the pineal gland influences the growth of the body and the development of the ovaries and testes, but the data available on this issue are somewhat contradictory. Therefore, nothing definite can be said about the endocrine function of the pineal gland.

INTERACTIONS OF ENDOCRINE GLANDS

For the sake of simplicity, we considered the action of each gland separately. Recent research, however, shows that almost every gland influences the function of almost every other gland.

Remember, for example, how the pituitary gland influences the ovaries, stimulating the formation of first estrogen and then progesterone. These hormones in turn influence the secretion of hormones by the pituitary gland itself. For example, progesterone suppresses the secretion of pituitary follicle-stimulating hormone, thereby preventing the start of a new menstrual cycle until the previous one has ended or until pregnancy has ended.

The intensity of cellular metabolism and the relative rate of use of carbohydrates, fats and proteins is regulated by the complex interaction of thyroxine, insulin, adrenaline, glucagon, growth hormone, hydrocortisone, estradiol and testosterone. For normal growth, not only growth hormone and thyroxine are needed, but also insulin, androgens and other hormones.

G. Selye has done a lot in recent years to study the role of hormones in the body's response to various strong influences (stress). Impacts such as surgery, burns, broken bones, or cold conditions cause the adrenal medulla to release adrenaline. Adrenaline acts on the pituitary gland, causing it to secrete ACTT, which in turn stimulates the adrenal cortex and causes it to release cortisone and other hormones.

Adrenal hormones cause changes in mineral and carbohydrate metabolism, helping the animal adapt to conditions of “overexertion”. Long-term acute exposures can eventually exhaust the body's adaptive capacity and cause exhaustion or shock. The intimate functional connection between the adrenal glands and the pituitary gland in similar and other situations gave rise to the idea of ​​the “adrenal-pituitary system” as a center that regulates the body’s adaptation to external influences.