relationship btwn ant pit and hypothalamus

relationship between hypothalamus and anterior pituitary gland

1. Department of Physiollogy Faculty of Basic Medical Sciences College of Health Sciences Benue State University ,Makurdi.   “the structural and functional relationship between the anterior pituitary gland and the hypothalamus” dr. eru e. u. course facilitator

2. THE HYPOTHALAMUS Hypothalamus is a diencephalic structure. It is situated just below thalamus in the ventral part of diencephalon.It has intimate anatomical and functunctinal reiationship with pituitary gland.It regulate the functions of other endocrine glands e.g thyriod,adrenal and gonads. It is formed by groups of nuclei, scattered in the walls and floor of third ventricle. It extends from optic chiasma to mammillary body.

3. the pituitary gland T he pituitary gland, also called the hypophysis . Has two distinct parts-Anterior (Adenohypophysis) and posterior pipuitary glands.(Nurohypophysis) It is a small gland—about 1 centimeter in diameter and 0.5 to 1 gram in weight— lies in the sella turcica , a bony cavity at the base of the brain It is connected to the hypothalamus via hypothalamo-hypophyseal portal vessels Network of blood vessels,whie that of posterior lobe is via the neural stalk.

4. Physiologically, the pituitary gland is made of two distinct portions or lobes The anterior pituitary, also known as the adenohypophysis, and The posterior pituitary , also known as the neurohypophysis . Between these is a small, relatively avascular zone called the pars intermedia .which is much less developed in human being but more functional in some lower animals.

5. Embryologically, the two lobes of the pituitary originate from different sources. The anterior pituitary originate from ectodermal cells of oral cavity ( Rathke’s pouch,) which is an embryonic UPWARD invagination of the pharyngeal epithelium.or oral cavity. The posterior pituitary originate from a neural tissue downward outgrowth from the third ventricle of the brain, T he origin of the posterior pituitary from neural tissue explains the presence of large numbers of glial-type cells in this gland

6. The anterior pituitary The anterior pituitary is subdivided anatomically into three parts . Pars distalis Pars tuberalis Pars intermedialis

7. Histology The anterior pituitary gland consists of two cells Chromophiles – are granular and constitute about 50% of all cells. The chromophiles is made up of acidophilic and basophilic cells. Chromophobes – are agranular and constitute 50% of all the cells. function is unknown   They act as supporting cells[structure]

8. Hormones of the anterior pituitary gland The hormones of adenohypophesis play major roles in the control of metaolic functions About 30 to 40 percent of the anterior pipuitary cells are somatotropea. The acidophilic somatotropes secrete two hormones. : Somatotropes - secrete the growth hormone (GH) .Stimulates cell growth and replication through release of somatomedins or IGF (Insulin growth factor) Mamotropes / lactotropes - secrete the prolactin (PRL )  stimulates the development of mammary gland and milk production.

9. The basophilic cells consist of Thyrotropes - secrete the thyroid stimulating hormone(TSH).control the rate of scretion of thyroxine and triiodothyronine. Corticotropes - secrete the adrenocorticotrophic hormone (ACTH) ACTH stimulates the release of glucocorticoids by the adrenal glands. Gonadotropes - secrete the follicle stimulating hormone (FSH) and luteinizing hormone (LH).FSH stimulates follicle development and estrogen secretion in females and sperm production from the ovaries and testes respectively. Leutinizing hormone (LH) causes ovulation and progesterone production in females and testosterone in males Melanocyte stimulating hormone (MSH)-stimulate melanocytes to produce melanin

10. Hormones of posterior pituitary The psterior pituitary gland is a bag of storage organ for hormones produce by the hypothalamus There are large neurons, called magnocellular neurons, located in the supraoptic and paraventricular nuclei of the hypothalamus. The two hormones are Ant-diurectic (vasopressin) and oxytocin. The hormones are then transported in the axoplasm of the neurons’ nerve fibers passing from the hypothalamus to the posterior pituitary gland.

11. The relationship between the anterior pituitary and the hypothalamus

12. Hypothalamus regulate the activity of anterior pituitary gland Through the secrection of stimulatory releasing or inhitory hormones. GH releasing hormone (GH_RH) Growth hormone inhibiting hormone (GH-IH) -Somatostatin Prolactin releasing hormone (PRH) Prolactin inhibiting hormone (PIH) Dopamine. Thyrotropin releaing hormone promote the release of TSH Corticotrophin releasing hormone causes the secretion of ACTH Gonadotropin releasing hprmone (GNRH) promotes the secretion of FSHand LH.

13. Feed back control The secretory activities of endocrine tissues are generally modulated by negative feed back e.g the concentration of hormone itself or a respone to the hormone by a target cell has an inhibitory effect on the synthesis or secretory process responsible for the elaboration of the hormone in question. Such feed back mechanism can ether be the short loop or long loop.

14. FUNCTIONAL RELATIONSHIP The functional relationship between the hypothalamus and the anterior pituitary is elicited in the regulatory control of the anterior pituitary by the hypothalamus.

15. REGULATION OF ANTERIOR PITIUTARY SECRETION Though the pituitary gland is regarded as the master e ndocrine gland, its activities are regulated by the hypothalamus Hypothalamus controls anterior pituitary by secreting the releasing and inhibitory hormones which are called neuro-hormones . Almost all secretions by the pituitary is controlled by either releasing or inhibiting hormonal signals from the hypothalamus.

16. Secretions by the anterior pituitary is regulated by hormones called hypothalamic-releasing and hypothalamic-inhibitory hormones secreted within the hypothalamus These hormones are then conducted to the anterior pituitary through minute blood vessels called hypothalamic- hypophyseal portal vessels .

17. Special neurons in the hypothalamus synthesize and secrete the hypothalamic releasing and inhibitory hormones that control secretions of anterior pituitary hormones. These neurons originate in various parts of the hypothalamus and send their nerve fibers to the median eminence and tuber cinereum , an extension of hypothalamic tissue into the pituitary stalk .

18. RELEASING AND INHIBITORY HORMONES SECRETED BY HYPOTHALAMUS . Growth hormone releasing hormone(GHRH): stimulates the release of growth hormone. Growth hormone inhibitory hormone (somatostatin) inhibits the release of GH

19. Corticotropic releasing hormone(CRH): stimulates the release of adrenocorticotropin . Gonadotropic releasing hormone( GnRH ): stimulates the release of gonadotropins , FSH and LH. Prolactin inhibitory hormones(PIH): inhibits prolactin secretion, can also be called dopamine .

20. Thyrotropic releasing hormone(TRH): stimulates the release of thyroid stimulating hormone.