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Posterior pituitary

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Definition

noun, plural: posterior pituitaries

The non-glandular posterior lobe of the pituitary gland that acts as the site for the secretion of neurohypophysial hormones such as oxytocin and vasopressin into the bloodstream


Supplement

The pituitary gland is an endocrine gland situated off the bottom of the hypothalamus. It acts as the master gland of the endocrine system because it is responsible for the release of different hormones that regulate many physiological processes. It consists of three lobes: (1) anterior, (2) intermediate, and (3) posterior.

The posterior lobe of the pituitary gland is referred to as the posterior pituitary. Unlike the anterior lobe, the posterior lobe is not glandular. Nonetheless, it also releases hormones, particularly oxytocin and vasopressin into the bloodstream.

The posterior pituitary is an extension of the hypothalamus. It is comprised of axonal projections from the hypothalamus that terminate behind the anterior lobe of the pituitary. Together with the paraventricular nucleus and the supraoptic nucleus of the hypothalamus, the posterior pituitary forms the hypothalamic-neurohypophyseal system. The axons of the magnocellular neurosecretory cells from the supraoptic and paraventricular nuclei of the hypothalamus store and release neurohypophysial hormones, oxytocin and vasopressin into the capillaries of the posterior pituitary. Specialized glial cells are also present in the posterior pituitary. They are called pituicytes that help in the storage and the release of the hormones.

Two parts of the posterior pituitary have been described: (1) pars nervosa and (2) infundibular (or pituitary) stalk. The pars nervosa forms the bulk of the posterior pituitary. It includes the Herring bodies and the pituicytes. This region serves as the storage site for oxytocin and vasopressin. The infundibular stalk (also called infundibulum or pituitary stalk) connects the hypothalamic and hypophyseal systems.

Desiccated pituirary (or hypophysis sicca) refers to the cleaned, dried, and powdered posterior lobe of the pituitary body of domesticated animals. It is obtained for use as food for humans. It is oxytocic, vasoconstrictor, antidiuretic, and a stimulant of intestinal motility.


Synonym(s):

  • neurohypophysis
  • posterior lobe of hypophysis
  • desiccated pituitary

See also: