Posterior Pituitary

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Summary

The posterior pituitary is one of two parts of the pituitary gland. Formed by a neural extension of the hypothalamus, the posterior pituitary does not make its own hormones. Instead, the hormones are made in the hypothalamus, and then delivered to the posterior pituitary to be stored until needed for release. Specifically, the posterior pituitary releases two hormones into the blood, oxytocin and vasopressin. Oxytocin plays roles in birth by stimulating uterine contractions. On the other hand, Vasopressin, also known as antidiuretic hormone, primarily works to increase water reabsorption in the kidneys.

Key Points

  • Posterior Pituitary
    • Structure:
      • Made up of axonal projections from hypothalamus
      • One of two lobes of pituitary gland, located beneath the Hypothalamus
    • Hormones Background:
      • Origin: Hormones made in hypothalamus
        • Stored in posterior pituitary
        • Posterior pituitary hormones are synthesized in the hypothalamus and undergo axonal transport to be stored in the posterior pituitary
      • Trigger: Neural signals from hypothalamus
        • Secretion of hormones is mediated by depolarization of the nerve terminals extending from the hypothalamus
      • Type: Peptide
    • Releases:
      • Vasopressin/Antidiuretic Hormone (ADH)
        • Increases water reabsorption
        • Stimulates collecting ducts of kidneys to reabsorb more water Increases blood pressure
      • Oxytocin 
        • Stimulates uterine contractions 
        • Stimulates milk ejections from breasts