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The anterior pituitary (also called the adenohypophysis or pars anterior) is a major organ of the endocrine system.The anterior pituitary is the glandular, anterior lobe that together with the (posterior pituitary, or the neurohypophysis) makes up the pituitary gland (hypophysis) which, in humans, is located at the base of the brain, protruding off the bottom of the hypothalamus.
In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary, which is an extension of the hypothalamus. [6] The height of the pituitary gland ranges from 5.3 to 7.0 mm. The volume of the pituitary gland ranges from 200 to 440 mm 3. [7]
The posterior pituitary is not glandular as is the anterior pituitary. Instead, it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior pituitary, and serve as a site for the secretion of neurohypophysial hormones (oxytocin and vasopressin) directly into the blood. [2]
The pituitary gland is divided into three lobes: the anterior pituitary, the intermediate pituitary lobe, and the posterior pituitary. The hypothalamus controls the anterior pituitary's hormone secretion by sending releasing factors, called tropic hormones, down the hypothalamo-hypophysial portal system. [3]
It consists of a hormone-producing glandular portion of the anterior pituitary and a neural portion of the posterior pituitary, which is an extension of the hypothalamus. The hypothalamus regulates the hormonal output of the anterior pituitary and creates two hormones that it exports to the posterior pituitary for storage and later release.
In posterior pituitary we have hormones that control absorption of water and oxytocin. Anterior hypophysis, neurosecretory cells which release hormones. There is a pituitary portal system, with which the hormones are transported. These hormones are prolactin, growth hormone, TSH, adrenocorticotropic hormone, FSH and LH.
The cells of the anterior pituitary express specific G protein-coupled receptors that bind to the neuropeptides, activating intracellular second messenger cascades that produce the release of anterior pituitary hormones. [4] The following is a list of hormones that rely on the hypophyseal portal system to indirectly mediate their function by ...
They then rapidly reach the anterior pituitary where they exert their hormonal action. The residual hormones pass into the systemic circulation where they are diluted, degraded and have comparatively little effects. The synthesis, control, and release of those hormones is co-regulated by hormonal, local and synaptic signals (neurotransmitters).