Gland – a special vital organs responsible for the production of biologically active substances, which fall through the ducts into the bloodstream, the cavity of the inner organs or onto the body surface. Depending on the function, allocate the glands of internal secretion. Endocrine glands do not have excretory ducts: their secret containing various types of hormones enters the blood and lymph, regulating the function of internal organs and affecting the tissues at the cellular level. To this type include the thyroid gland, hypophysis, epiphysis, adrenal glands, and some others. The glands of external secretion secrete hormones into the body surface: it is of salivary, sweat, mammary glands.
The mixed type of secretion include the pancreas and sex glands. Their secret at the same time involved in the maintenance of the internal physiological processes of the body and external influences on organisms vyrabatyvaet on the surface of the body. Glands mixed secretions are multifunctional. In particular, the pancreas consists of two types of cells. Part of this body produces a special substance rich in enzymes necessary for the digestion and processing of protein foods. The other part of the pancreas produces a hormone involved in glucose uptake by body cells.
To a mixed type also include female and male sex glands. In the follicles of the ovaries in women are synthesized estrogen, yellow body in the ovary produces progesterone. It is thanks to the estrogen women gain characteristic external features in puberty. These hormones are responsible for the development of sexual characteristics and full development of the internal reproductive organs, which is necessary to reproduce healthy offspring. Progesterone plays an important role in the pregnancy: the hormone prepares the uterus to the appearance of the embryo and control growth and development, protecting the expectant mother from miscarriage.
The testes are formed androgens, male sex hormones. Testosterone and Androsterone hormones responsible for male sexual characteristics and is involved in the normal functioning of the male reproductive system. Without a stable operation of male sex glands it is impossible the maturation of sperm and, therefore, cannot procreate.