Endocrine gland

A endocrine gland is a Organe intern (a Glande) which secretes Hormone S in circulation Sang uine, which then exert their specific action on bodies or cell-targets distant. The hormones act as chemical messengers, controlling many functions of the organization such as the growth, the development, the reproduction, the Métabolisme, the blood Pressure, the Glycémie and balances it fluids. One finds glands endocrine at the majority of the animals, including at the Invertébrés.

Operation of the system endocrinien

The animals have, in addition to the immune system, two great communication networks internal: the Nervous system and the System endocrinien. The apparatus endocrinien transmits its messages thanks to the secretion of the hormones, generally of the Peptide S or the Protéine S, while the nervous system uses the Neuron S, which release from the Neurotransmetteur S in the Synapse S to transmit the nerve impulse to other neurons. But these two systems have major interrelationships, since certain neurons also synthesize peptides, called neuropeptides , which are then released in blood circulation: for example, in the mammals, the nervous fibers hypothalamic with Somatostatine or Hormone thyréotrope (TRH) release in the median eminence their products of Sécrétion, which reach the former Hypophyse via the vessels of the Système carries.

The endocrine epithelium S glandular can be in form:

of well individualized endocrine glands (ex: Thyroid, Pituitary gland, Testicle S, ovary S…)
of endocrine clusters of cells (ex: small islands of Langerhans of the Pancreas, Cells of Leydig of the testicles)
dispersed, diffuses, within other bodies (ex: endocrine cells of the digestive tract, like the cells with gastrine of the Stomach, cells with secretin of the Duodenum, or cells with glicentine of the Colonist).

Certain glands are mixed, associating an endocrine part and a part exocrine, like the Gonades (testicles and ovaries) or the Pancréas, secreting about the external middle, generally via channels excréteurs.

In the mammals, the pure endocrine glands are the Thyroïde, the Parathyroïde S, the Surrénale S, the Hypophyse, the pineal Body (or épiphyse). In the arthropods, one can quote the Glande of moult.

Lastly, other bodies can also play a certain endocrine part: for example, the cells of grease (or adipocytes) secrete Leptine; the ovaries and the testicles produce the gamètes naturally, but they also have an endocrine function.

During the pregnancy, the Placenta also plays the part of an endocrine gland; he becomes the principal producer of hormones steroids. The hormones produced by these glands can be Peptide S (for example the TRH) or Protéine S (for example insulin); steroids like the estrogen , the Progesterone and the Testosterone; or of derived from amino-acids like the thyroid hormones.

List principal endocrine glands at the vertebrate ones

Thyroid Pituitary gland
Suprarenal
Ovary or Parathyroid Testicle
Pancreas
Thymus

Principal endocrine glands in the invertebrates (arthropods)

Gland of moult
Ovary or allato-cardiac Testicle
Complex

See too

Endocrinology

External bond

Animation endocrine glands

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