The pituitary gland, also known as the hypophysis, is a small gland located at the base of the brain. It has an anterior and posterior lobe with different developmental origins and functions. The anterior lobe produces several hormones that regulate other endocrine glands and other processes. These include growth hormone, thyroid stimulating hormone, adrenocorticotropic hormone, follicle stimulating hormone, luteinizing hormone, and prolactin. The posterior lobe stores and releases antidiuretic hormone and oxytocin, which are produced in the hypothalamus. The pituitary gland plays a key role in regulating many physiological processes through its interaction with the hypothalamus via the hypothalamic-hypophyseal portal system

1. Pituitary gland Dr. Saddam Ansari Georgia 13thFebruary 2011

3. IntroductionKnown as HypophysisSmall gland Weight is 0.5 – 1 gmDimension is approximately (10×13×6)mm.

5. DevelopmentAnterior pituitaryEctodermal in originArises from pharyngeal epithelium as an upward growth known as Rathke’s pouchPosterior pituitaryNeuroectodermal in originArises from base of the Diencephalon as a downward diverticulumknown as Infundibulam

6. Continued…The Rathke’s pouch and downward diverticulum from hypothalamus meet midway betweenThe roof of the buccal cavity and Base of the brain

8. AnatomyLocationLies at the base of brain in Sella turcica.Connected with the Hypothalamus by the pituitary stalk or hypophyseal stalk.

10. Continued…Divided into two portions:Anterior pituitary or AdenohypophysisPosterior pituitary or NeurohypopysisBetween 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 approximationBut they are entirely different in their:DevelopmentStructure Function

12. Blood supply2 pairs of vessels coming off the internal carotid arterySuperior hypophyseal arteriesSupply the Median eminence and the Infundibular stalkInferior hypophyseal arteries Supply the Neurohypophysis with small supply to the stalk.

14. Continued…Primary capillary network and Secondary capillary network are formed.Capillaries are fenestratedHypothalamo-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 sites1. Peptide hormones synthesized by neurons by specific nuclei in hypothalamusSupraopticParaventricular Hormones are accumulated in the axons situated in Pars nervosa

17. Continued…2. Another group of peptides produced by neurons in other hypothalamic nucleiCarried in axons for temporary axonal storage and secretion in Median eminenceThese peptides enters primary plexus and transported to the Adenohypophysisand control hormone release

18. Continued…3. Group of hormones consists of Proteins GlycoproteinsReleased from endocrine cells of Pars distalis and diffused into capillaries of the second portal system plexus

19. Anterior pituitaryConsists of three divisionsPars distalisPars tuberalisPars intermedia

21. Histology of AdenohypophysisDepending upon the staining property-2 typesChromophobe cellsChromophil cells

23. Continued…Chromophobe cellsDo not possess granules Stained poorly Cells are not secretory in natureBelieved to be the precursors of chromophil cellsComprises about 50% of total cells

24. Continued…Chromophil cellsContain large number of granulesDarkly stained2 types based on staining natureAcidophilic or Alpha cells - 35%Basophilic or Beta cells - 15%

25. Continued… 5 types based on secretory natureSomatotropeswhich secrete growth hormoneCorticotropes which secrete adrenocorticotropic hormoneThyrotropes which secrete thyroid stimulating hormoneGonadotropes which secrete follicle stimulating and Luteinizing hormoneLactotropes which secrete prolactin

26. physiology

27. Regulation of secretionHypothalamo-Hypophyseal RelationshipHypothalamus secretes several hormones to the Anterior pituitary Posterior pituitaryTransportation of hormones To Anterior pituitary by Hypothalamo-Hypophyseal portal systemTo Posterior pituitary by nerve fibers of Hypothalamo-Hypophyseal tract

28. Continued…Regulation of Anterior Pituitary SecretionHypothalamus controls Anterior Pituitary through releasing and inhibitory hormones called neurohormones

29. Continued…Releasing and Inhibitory Hormones by HypothalamusGrowth hormone releasing hormone (GHRH)Stimulates the release of growth hormoneGrowth hormone releasing polypeptide (GHRP)Stimulates release of GHRH and growth hormoneGrowth hormone inhibitory hormone (GHIH) or SomatostatinInhibits growth hormone release

30. Continued…Thyrotropic releasing hormone (TRH)Stimulates the release of thyroid stimulating hormoneCorticotropin releasing hormone (CRH)Stimulates the release of adrenocorticotropinGonadotropin releasing hormone (GnRH)Stimulates the release of gonadotropinsProlactin inhibitory hormone (PIH)Inhibits prolactin secretion

31. Hormones Secreted by AdenohypophysisGrowth hormone (GH) or Somatotropic hormone (STH)Thyroid stimulating hormone (TSH) or Thyrotropic hormoneAdrenocorticotropic hormone (ACTH)Follicle stimulating hormone (FSH)Luteinizing hormone (LH in females) or Interstitial cell stimulating hormone (ICSH in males)Prolactinβ- Lipotropin (recent)

33. Thank you