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Pituitary gland

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Physiology and Anatomy

Physiology and Anatomy

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Transcript

  • 1. Pituitary gland
    Dr. Saddam Ansari
    Georgia
    13thFebruary 2011
  • 2.
  • 3. Introduction
    Known as Hypophysis
    Small gland
    Weight is 0.5 – 1 gm
    Dimension is approximately (10×13×6)mm.
  • 4.
  • 5. Development
    Anterior pituitary
    Ectodermal in origin
    Arises from pharyngeal epithelium as an upward growth known as Rathke’s pouch
    Posterior pituitary
    Neuroectodermal in origin
    Arises from base of the Diencephalon as a downward diverticulumknown as Infundibulam
  • 6. Continued…
    The Rathke’s pouch and downward diverticulum from hypothalamus meet midway between
    The roof of the buccal cavity and
    Base of the brain
  • 7.
  • 8. Anatomy
    Location
    Lies at the base of brain in Sella turcica.
    Connected with the Hypothalamus by the pituitary stalk or hypophyseal stalk.
  • 9.
  • 10. Continued…
    Divided into two portions:
    Anterior pituitary or Adenohypophysis
    Posterior pituitary or Neurohypopysis
    Between the two portions Pars intermedia is present.
    Very small in humans
    More functional in lower animals
  • 11. Continued…
    Anterior and Posterior pituitary are situated in very close approximation
    But they are entirely different in their:
    Development
    Structure
    Function
  • 12. Blood supply
    2 pairs of vessels coming off the internal carotid artery
    Superior hypophyseal arteries
    Supply the Median eminence and the Infundibular stalk
    Inferior hypophyseal arteries
    Supply the Neurohypophysis with small supply to the stalk.
  • 13.
  • 14. Continued…
    Primary capillary network and Secondary capillary network are formed.
    Capillaries are fenestrated
    Hypothalamo-Hypophyseal portal system is formed.
    Carries neuropeptides from the median eminence to the Adenohypophysis where they either stimulate or inhibit hormone release
  • 15. Continued…
    In Hypothalamo-Hypophyseal system there are 3 groups of hormones released at 3 sites
    1. Peptide hormones synthesized by neurons by specific nuclei in hypothalamus
    Supraoptic
    Paraventricular
    Hormones are accumulated in the axons situated in Pars nervosa
  • 16.
  • 17. Continued…
    2. Another group of peptides
    produced by neurons in other hypothalamic nuclei
    Carried in axons for temporary axonal storage and secretion in Median eminence
    These peptides enters primary plexus and transported to the Adenohypophysisand control hormone release
  • 18. Continued…
    3. Group of hormones consists of
    Proteins
    Glycoproteins
    Released from endocrine cells of Pars distalis and diffused into capillaries of the second portal system plexus
  • 19. Anterior pituitary
    Consists of three divisions
    Pars distalis
    Pars tuberalis
    Pars intermedia
  • 20.
  • 21. Histology of Adenohypophysis
    Depending upon the staining property-2 types
    Chromophobe cells
    Chromophil cells
  • 22.
  • 23. Continued…
    Chromophobe cells
    Do not possess granules
    Stained poorly
    Cells are not secretory in nature
    Believed to be the precursors of chromophil cells
    Comprises about 50% of total cells
  • 24. Continued…
    Chromophil cells
    Contain large number of granules
    Darkly stained
    2 types based on staining nature
    Acidophilic or Alpha cells - 35%
    Basophilic or Beta cells - 15%
  • 25. Continued…
    5 types based on secretory nature
    Somatotropeswhich secrete growth hormone
    Corticotropes which secrete adrenocorticotropic hormone
    Thyrotropes which secrete thyroid stimulating hormone
    Gonadotropes which secrete follicle stimulating and Luteinizing hormone
    Lactotropes which secrete prolactin
  • 26. physiology
  • 27. Regulation of secretion
    Hypothalamo-Hypophyseal Relationship
    Hypothalamus secretes several hormones to the
    Anterior pituitary
    Posterior pituitary
    Transportation of hormones
    To Anterior pituitary by Hypothalamo-Hypophyseal portal system
    To Posterior pituitary by nerve fibers of Hypothalamo-Hypophyseal tract
  • 28. Continued…
    Regulation of Anterior Pituitary Secretion
    Hypothalamus controls Anterior Pituitary through releasing and inhibitory hormones called neurohormones
  • 29. Continued…
    Releasing and Inhibitory Hormones by Hypothalamus
    Growth hormone releasing hormone (GHRH)
    Stimulates the release of growth hormone
    Growth hormone releasing polypeptide (GHRP)
    Stimulates release of GHRH and growth hormone
    Growth hormone inhibitory hormone (GHIH) or Somatostatin
    Inhibits growth hormone release
  • 30. Continued…
    Thyrotropic releasing hormone (TRH)
    Stimulates the release of thyroid stimulating hormone
    Corticotropin releasing hormone (CRH)
    Stimulates the release of adrenocorticotropin
    Gonadotropin releasing hormone (GnRH)
    Stimulates the release of gonadotropins
    Prolactin inhibitory hormone (PIH)
    Inhibits prolactin secretion
  • 31. Hormones Secreted by Adenohypophysis
    Growth hormone (GH) or Somatotropic hormone (STH)
    Thyroid stimulating hormone (TSH) or Thyrotropic hormone
    Adrenocorticotropic hormone (ACTH)
    Follicle stimulating hormone (FSH)
    Luteinizing hormone (LH in females) or Interstitial cell stimulating hormone (ICSH in males)
    Prolactin
    β- Lipotropin (recent)
  • 32.
  • 33. Thank you