Human Anatomy (with Fundamentals of Dynamic and Sports Morphology) - Ivanitsky, M. F. 2008

The Doctrine of Internal Secretion Organs
Adrenal Gland

The Adrenal Glands are paired endocrine Organs, each weighing approximately 10–15 g in an adult. The right Adrenal gland is triangular in shape, while the left is semilunar (crescent-shaped). The base of each gland rests on the upper pole of the corresponding Kidney, and its posterior surface is adjacent to the Diaphragm (see Fig. 79).

Each adrenal gland is enclosed within a capsule and consists of an outer cortex and an inner medulla. These two portions differ significantly in their origin, Structure, and function. Thus, much like the Pituitary Gland, the adrenal gland is an anatomical combination of two distinct organs.

The adrenal cortex is subdivided into three distinct zones: the outer zona glomerulosa, the middle zona fasciculata, and the inner zona reticularis.

The zona glomerulosa is composed of small, rounded adrenocortical Cells that produce mineralocorticoids, which regulate Water and Electrolyte balance (predominantly within the Kidneys).

The zona fasciculata is formed by larger cells that secrete glucocorticoid Hormones, which regulate carbohydrate and Protein METABOLISM.

The zona reticularis consists of a loose network of small adrenocortical cells exhibiting considerable morphological Variability. They produce androgens (Male Sex Hormones) and, to a lesser extent, Female Sex Hormones.

The cortical Hormones of the adrenal gland are classified into glucocorticoids, mineralocorticoids, and corticosteroids. The first group influences carbohydrate and protein metabolism, the second regulates water and electrolyte balance (specifically the Blood concentrations of sodium, potassium, and chloride ions), and the third is structurally and functionally related to sex hormones. According to Hans Selye, the adrenal glands mediate a non-specific defense syndrome, commonly known as the stress response, in reaction to harmful stimuli affecting the body (see p. 493).

The adrenal medulla is closely related in its embryonic development to the sympathetic Nervous system. It contains large cells whose Cytoplasm is rich in fine granules. These cellular granules stain dark brown upon exposure to chromium salts, which is why the medullary tissue is classified as part of the Chromaffin System. In addition to chromaffin cells, sympathetic Nerve Cells are also present within the medulla.

The adrenal medulla secretes adrenaline (epinephrine) and noradrenaline (norepinephrine), which enter the bloodstream and exert an excitatory effect on the sympathetic nervous system. Through this pathway, these hormones act on the Cytology/cytology/32.html">Smooth Muscle tissue of Blood Vessels and Internal Organs. They enhance myocardial contractility and excitability, constrict cutaneous blood vessels, raise blood pressure, and decrease the tone of the gastrointestinal tract.