Posterior pituitary gland

ROBERT IGBEDE

1. POSTERIOR PITUITARY GLAND BY ROBERT IGBEDE

2. Introduction The pituitary gland or hypophysis hangs from the hypothalamus by its neck called the infundibulum and is located within in the hypophyseal fossa (deepest part of sella turcica ) of the shenoid bone It is divided into an anterior lobe or adeno-hypophysis and a posterior lobe or neuro-hypophysis , both seperated by a thin lamina

3. Neuro-hypophysis The neuro-hypophysis or posterior pituitary gland is called neurohypophysis because is derived from the neural crest during embryonic development It is called posterior pituitary because it is located posteriorly on the pituitary gland It is the smaller of the two lobes

4. Structure The PPG is highly vacularized . It has a capillary system which is supplied by the inferior hypophyseal artery It contains the nerve endings of the neurons( magnocellular) that begin in the hypothalamus This neurons have their soma embedded in the paraventricular and supraoptic nuclei of the hypothalamus Contains glial cells ( pituicytes ) that support this neurons

5. Function The posterior pituitary gland does not synthesize or secrete any hormone itself. The hormones are synthesized in the soma of the neurons in the hypothalamus and travels within secretory vessicles by anterograde transport to the axon which lies in the posterior pituitary gland and is stored in the posterior pituitary gland This migration of the secretory vesicle through the axoplasm of the neuron is facilitated by a carrier protein called neurophysin

6. Storage There are two hormones that are stored in the posterior pituitary gland 1) ADH (vasopressin): anti diuretic hormone is synthesized primarily in the soma of the supraoptic nuclei found in the hypothalamus 2) Oxytocin : it is synthesized primarily in the soma of paraventricular the nuclei

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