Pituitary gland (1)

Anatomy and Physiology of pituitary gland

1. Pituitary Gland Subject faculty: Mr. Khurram Presenter: Maryam Noor 7/23/2018 1 Maryam Noor

2. Objectives: Define pituitary gland. Discuss the anatomy of the pituitary gland. Discuss the role of hypothalamic hormones in the regulation of pituitary gland secretion. Discuss the function of hormones secreted from the anterior and posterior pituitary gland. 7/23/2018 2 Maryam Noor

3. Pituitary Gland “The Master gland of the body” Pituitary gland is the small structure in the head and main endocrine gland . The normal adult pituitary gland is a reddish-grey bean shaped gland. It is also called the Master gland because it produces the hormones that control other glands and many body functions including growth. 7/23/2018 3 Maryam Noor

4. Anatomy of Pituitary Gland: The pituitary gland is a pea sized, weighs 500 mg located at the base of brain. It is 1cm in diameter. The pituitary gland lies in the Hypophyseal fossa (Sella turcica) of the Sphenoid bone below the hypothalamus . A fold of durameter covers the pituitary gland and has an opening for the passage of infundibulum (stalk) connecting the gland to the hypothalamus. 7/23/2018 4 Maryam Noor

5. Pituitary gland in hypophyseal fossa of sphenoid bone 7/23/2018 5 Maryam Noor

6. Para ventricular nucleus Supra-optic nucleus Pituitary portal system Hypothalamo-hypophyseal tract Posterior lobe Pituitary stalk Anterior lobe Intermediate lobe Figure 9.3   The pituitary gland.  The lobes of the pituitary gland and their relationship with the hypothalamus. Third ventricle 7/23/2018 6 Maryam Noor

7. Division of pituitary gland It consists of two main parts that originate from different type of cells. Anterior pituitary gland (Adeno hypophysis): It is an up growth of glandular epithelium from the pharynx. It secrete peptide hormones. Posterior pituitary gland (neurohypophysis): It is formed from the nervous tissue and nerve cells, surrounding by supporting glial cells (pituicytes). It stores hormones secreted by the hypothalamus. 7/23/2018 7 Maryam Noor

8. Relation of Hypothalamus and Pituitary gland  The connection between the hypothalamus and the pituitary gland results from hormones released from the hypothalamic neurons. The hypothalamus has two different connections with the pituitary gland. The connection to the adenohypophysis (the anterior lobe) is via a special portal blood system. Whereas the connection to the neurohypophysis (the posterior lobe) is directly through neurons. 7/23/2018 8 Maryam Noor

9. Blood supply to pituitary gland Arterial blood supply: Superior and inferior hypophyseal arteries, branches of internal carotid. Anterior lobe is supplied indirectly by blood (from hypothalamus). Posterior lobe is supplied directly. Venous drainage: Containing hormones from both lobes, venous blood leaves the gland and enter the venous sinuses between the layers of durameter. 7/23/2018 9 Maryam Noor

10. Para ventricular nucleus Supra-optic nucleus Pituitary portal system Hypothalamo-hypophyseal tract Posterior lobe Pituitary stalk Anterior lobe Intermediate lobe Figure 9.3   The pituitary gland.  The lobes of the pituitary gland and their relationship with the hypothalamus. Third ventricle 7/23/2018 10 Maryam Noor

11. Hormones of the pituitary gland The hormones of the pituitary gland send signals to other endocrine glands to stimulate or inhibit their own hormone production. For example, the anterior pituitary lobe will release adrenocorticotropic hormone (ACTH) to stimulate cortical production in the adrenal glands when you’re stressed. The anterior lobe releases hormones upon receiving releasing or inhibiting hormones from the hypothalamus. These hypothalamic hormones tell the anterior lobe whether to release more of a specific hormone or stop production of the hormone. 7/23/2018 11 Maryam Noor

12. Hormones produced by anterior pituitary gland Growth hormone (GH) Thyroid-stimulating hormone (TSH) Adrenocorticotrophic hormone (ACTH) Prolactin (PRL) Gonadotrophins Luteinizing hormone (LH) Follicle-stimulating hormone (FSH ) 7/23/2018 12 Maryam Noor

13. Growth hormone: Its release is stimulated by GHRH (growth hormone releasing hormone) suppressed by GHRIH (growth hormone release inhibiting hormone) secreted by hypothalamus. Secretion is also stimulated by hypoglycemia, exercise and anxiety. Secretion is greater during night sleep than day. GHRIH also suppress the secretion of TSH and gastrointestinal secretion, e.g. gastric juice, gastrin and cholecystokinin. 7/23/2018 13 Maryam Noor

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15. Thyroid Stimulating Hormone(TSH) The release of this hormone is stimulated by the Thyrotrophin Releasing Hormone(TRH) from the hypothalamus. It stimulates the growth and activity of thyroid gland. Thyroid gland secretes the thyroxine (T4) and Tri-Iodothyronine (T3). Its level is highest during the night. When blood level of thyroid hormone is high, secretion of TSH is reduced. 7/23/2018 15 Maryam Noor

16. Thyroid system 7/23/2018 16 Maryam Noor

17. Adrenocorticotrophic hormone(ACTH) ACTH secretion is stimulated by the release of Corticotrophin releasing hormone(CRH) from hypothalamus. ACTH level is highest at midday and lowest at midnight. It stimulates the synthesis and secretion of adrenal cortical hormone. It is stimulated by the hypoglycemia, stress, exercise and other emotional states. Its secretion is suppressed when blood level of ACTH rises. 7/23/2018 17 Maryam Noor

18. Prolactin This hormone is secreted during pregnancy for lactation. It is stimulated by prolactin releasing hormone (PRH) from hypothalamus. After birth suckling stimulate the Prolactin secretion and lactation. 7/23/2018 18 Maryam Noor

19. Gonadotrophins (FSH and LH) Just before puberty two Gonadotrophins are secreted in gradually increasing amounts by the anterior pituitary gland. Its secretion is stimulated by Gonadotrophin releasing hormone ( GnRH ) or luteinizing releasing hormone (LRH) from hypothalamus. Rising level of this hormone during puberty enhances the maturation of reproductive organs. 7/23/2018 19 Maryam Noor

20. Cont.. Gonadotrophin is combination of: Follicle stimulating hormone(FSH) Luteinizing hormone(LH) Follicle stimulating hormone: In both male and female it stimulates the production of gametes (ova and sperms from ovaries and testis respectively). 7/23/2018 20 Maryam Noor

21. Luteinizing hormone(LH) IN FEMALES: LH and FSH stimulate the secretion of Oestrogen and Progesterone from corpus luteum during the menstrual cycle. As the level of oestrogen and progesterone rises in blood, secretion of LH and FSH is suppressed. IN MALES: LH also called interstitial cell stimulated releasing hormone (ICSH). It stimulates the interstitial cells to secrete testosterone. 7/23/2018 21 Maryam Noor

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23. Posterior Pituitary Gland: Posterior pituitary hormones are synthesized in the nerve cells bodies, transported along the axons and stored in vesicles within the axon terminals in the posterior pituitary gland. Nerve impulses from hypothalamus trigger the exocytosis of vesicles (of pituitary gland) releasing their hormone into blood stream. Axon terminal release these two hormone within the posterior pituitary gland. Oxytoxin Antidiuritic hormone (ADH, Vasopressin) 7/23/2018 23 Maryam Noor

24. Neurons Vesicles containing the hypothalamic hormone: ADH and Oxytocin. Pituicyte Axon terminal Hypothalamus Posterior pituitary Capillary in posterior pituitary Figure 9.3   The pituitary gland. B. synthesis and storage of ADH and Oxytocin. 7/23/2018 24 Maryam Noor

25. Oxytocin It is also called anti stress hormone. Oxytocin is produced in both males and females, but its main physiological roles seem to take place in the female. In the female, oxytocin is involved in a number of important physiological actions: Stimulates the contraction of the uterus (myometrium) Stimulates the contraction of the myoepithelial cells that eject milk from the breast. 7/23/2018 25 Maryam Noor

26. Uterine muscle contraction Sensory stretch receptors in the uterine cervix (due to baby’s head) stimulate the release of oxytocin. Oxytocin stimulates the more forceful contraction of cervix, as the baby’s head is forced further downwards. It is also used clinically for the induction of labor. 7/23/2018 26 Maryam Noor

27. Milk Ejection Suckling generates sensory impulses that are transmitted from breast to the hypothalamus. This impulses triggers the release of oxytocin from posterior pituitary gland. Oxytocin stimulates the contraction of the milk ducts and myoepithelial cells for ejection of milk. Suckling also inhibits the release of Prolactin inhibiting hormone (PIH) prolonging Prolactin secretion and lactation. 7/23/2018 27 Maryam Noor

28. Antidiuritic hormone (ADH, Vasopressin). The main effect of the antidiuretic hormone is to reduce urine output (diuresis is the production of a large amount of urine) therefore it is called Antidiuritic. Its secretion is determined by osmotic pressure by circulating osmoreceptors in blood. Increase water intake > decrease in ADH > increase in urine output. Decrease in water intake > Increase in ADH > Decrease in urine output. 7/23/2018 28 Maryam Noor

29. ADH It acts on the distal convoluted tubules and collecting ducts of the nephrons of kidneys. Q. Why is it called vasopressin? Higher water concentration increases the volume and pressure of your blood. Vasopressin raises  blood pressure  by constricting (narrowing) blood vessels.  7/23/2018 29 Maryam Noor

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31. Growth hormone (GH) Thyroid stimulating hormone (TSH) Adrenocorticotrophic hormone(ACTH) Prolactin (PRL) Follicle stimulating hormone  (FSH Luteinizing hormone (LH) Regulates metabolism, promotes tissue growth especially of bones and muscles. Stimulates growth and activity of thyroid gland and secretion of T3 and T4. Stimulates the adrenal cortex to secrete glucocorticoids. Stimulates growth of breast tissue and milk production. Stimulates production of sperm in the testes, stimulates secretion of oestrogen by the ovaries, maturation of ovarian follicles, ovulation. Stimulates secretion of testosterone by the testes, stimulates secretion of progesterone by the corpus luteum. Hormone Function Table 9.2 Summary of the hormones secreted by the anterior pituitary gland and their functions 31 Maryam Noor

32. References: Ross and Wilson,2014 Anatomy and Physiology in health and illness (ed.14 th ). London. Churchill Livingstone Elsevier. Anne Waugh. https;//www.pituitary.org.uk/information/hormones/ https://www.healthline.com/human-body-maps/pituitary-gland 7/23/2018 32 Maryam Noor

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