08-12-2012, 03:00 PM
Pituitary Hormones :Structure & Mechanism of Action.
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Introduction
Endocrine system :
The endocrine system is a system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body. The endocrine system is in contrast to the exocrine system, which secretes its chemicals using ducts
A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland).
A hormone is a biologically active substance,product of specific metabolism of specialized cells of endocrine glands or single neuroendocrine cells, which exert regulatory effects on metabolism and physiological functions .It is a chemical messenger that transports a signal from one cell to another.
Anterior Pituitary :
A major organ of the endocrine system, the anterior pituitary, also called the adenohypophysis, is the glandular, anterior lobe of the pituitary gland. The anterior pituitary regulates several physiological processes including stress, growth, and reproduction.
Its regulatory functions are achieved through the secretion of various peptide hormones that act on target organs including the adrenal gland, liver, bone, thyroid gland and gonads. The anterior pituitary itself is regulated by the hypothalamus and by negative feedback from these target organs.
Intermediate Pituitary :
Pars intermedia is the boundary between the anterior and posterior lobes of the pituitary.
Posterior Pituitary :
The posterior pituitary (or neurohypophysis) comprises the posterior lobe of the pituitary gland and is part of the endocrine system.