Endocrine glands. What can you learn about them from the name? Firstly, they are called glands, since they consist only of special secretory cells and have the appearance of glandular formations. Secondly, the term "internal secretion" suggests that the secretions of these glands do not pass through the excretory channels. The glands have no such paths. They transfer their substances directly to the lymph or to the blood vessels that also enclose these glands. Thirdly, the purpose of these entities is secretory activity. The secret (or, in other words, secretions) of these glands is one or another hormone.
The endocrine glands supply the human body with hormones of a different nature. Some are made up of proteins, others are made up of their breakdown products, others are derived from fats such as cholesterol in its various forms. However, regardless of the nature of hormones, they all have a special purpose, which distinguishes them in a separate group of substances.
In order for a substance secreted by the cells of one or another organ to be called a hormone, and the organ that produces it to be included in the category of the “human gland”, it must have the following properties:
1. Hormones are very active in physiological processes. This property manifests itself in the fact that the slightest change in the direction of increasing or decreasing the amount of a given substance in the body causes a malfunction in its work. For this reason, it is very dangerous to take hormonal drugs in uncontrolled doses. For each organism, this dose should be set individually after serious examinations.
2. Hormones are very selective. Each of them works only with certain bodies and does not interfere with the activities of other systems.
3. In terms of lifespan, hormones can be compared with one-day butterflies. They are produced, quickly perform their work, and then are destroyed and excreted from the body. This must be taken into account when passing tests. At different periods of the year, month, and even time of day, the human body will have a different amount of hormones. Moreover, some of them are produced only at a certain age or condition of the body.
After studying the properties of secretions (secrets) of various human organs, scientists found that only some cells secrete hormones. These cells began to be called secretory (capable of producing hormones), and the organs containing them were isolated into a separate system. So the glands of internal secretion entered into science. To date, only a few of them are well studied, namely the pituitary gland, the sex glands, adrenal glands, and the thyroid gland.
The structure of the endocrine glands is very difficult to study, since they are all located deep in the body, closed by other organs: the skull, kidneys, stomach, etc. In addition, the size of the glands is very small, which also complicates their study. The main source of information about a particular iron is the hormones it produces. The activity of hormones is studied through the study of blood and the effect that they have on the whole body.
It is also interesting that the list of endocrine glands is not final today. Science and medicine do not stand still. New technologies provide an opportunity to better and more detailed study the structure of tissues and cells of already familiar organs, to identify all the new functions that they perform.
In recent years, it has become known that some organs in their composition, as well as endocrine glands, have a small number of secretory cells that can produce substances similar in action to hormones. So, for example, it was found that the duodenum produces secretin, which affects the functioning of the pancreas. The kidneys with their secretions can change blood pressure. The spleen provides a substance that stimulates the bone marrow to produce red bodies. It is likely that further study of these cells will significantly expand the list of organs that perform endocrine functions in the human body.