Pituitary gland


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Pituitary gland

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