Human Anatomy Part 1 - K. A. Dyubenko, A. K. Kolomiysev, Yu. B. Chaykovsky 2002

Special Part
Endocrine glands (ductless glands), glandulae endocrinae (glandulae sine ductibus)

Endocrine glands, glandulae endocrinae (from endo – inside, crino – to secrete), or Glands of Internal Secretion. They consist of Organs and isolated hormone-producing Cells that release biologically active specific substances—Hormones (from the Greek hormao meaning to excite)—directly into the internal environment of the body. Hormones play an active role in regulating Homeostasis, METABOLISM, reproduction, somatic growth, and the differentiation of Cells and Tissues.

Endocrine glands perform integrative, coordinating, and regulatory Functions in close interaction with The Nervous system. The morphological substrate for this functional relationship between the endocrine and nervous systems is their rich innervation, alongside specialized regions within the Central Nervous System that integrate neural and humoral regulation. In particular, these include areas containing neurosecretory cells that exhibit properties of both endocrinocytes and neurocytes. Unlike exocrine glands, endocrine glands lack excretory ducts. Because they release their secretions directly into the bloodstream, they are heavily vascularized and possess a well-developed Hemomicrocirculatory bed. The capillary network of endocrine glands comprises fenestrated or sinusoidal capillaries, ensuring the rapid delivery of hormones into the body's internal environment.

All endocrine glands of The Human Body, including isolated hormone-producing cells, are the subject of study in endocrinology—the science of their Structure, function, MECHANISM OF ACTION, and pathology. Endocrine cells are not only constituents of independent organs within the Endocrine System; they can also be found within non-endocrine organs. These structures are divided into central and peripheral divisions that interact with one another to form a unified endocrine system.

According to B. V. Alyoshin's Classification, endocrine glands are categorized into four morphofunctional components.

1. Central Regulatory Organs:

- Hypothalamus;

- Pituitary Gland (hypophysis);

- Pineal Gland (epiphysis).

- Thyroid Gland;

- Parathyroid glands;

- Adrenal Glands.

3. Organs combining endocrine and non-endocrine functions:

- Pancreas;

- Gonads (Testis, Ovary);

- Placenta.

4. Isolated hormone-producing cells:

- neuroendocrine cells of neural origin;

- isolated hormone-producing cells of non-neural origin.