Anatomy hypothalamus and the pituitary.pptx

An overview of the pituitary gland in humans

1. Anatomy hypothalamus and the pituitary

2. Introduction Hypothalamus produces neuroendocrine substances that instruct the pituitary gland to produce (and in some instances to inhibit) its hormones Pituitary gland once stimulated produces hormones that stimulate other peripheral gland to produce their hormones (few pituitary hormones are the once responsible for direct physiologic hormones)

3. HYPOTHALAMUS It’s the portion of anterior of diencephalon that lies in front of the hypothalamic sulcus Its divided into a variety of nuclei areas which serves various roles in homeostasis There is a zone called the median eminence which is rich in fenestrated capillary network Some of its nuclei has axons that project down to the pituitary gland.

4. S tructure

5. Various hypothalamic nuclei Hypothalamic nucleus Function Dorso -medial Feeding and drinking Supra- chiasmatic Circadian rhythms Posterior hypothalamic Thermoregulation Mamillary body Recollective memory Preoptic area Thermoregulation Ventromedial Fear and sexual activity Anterior hypothalamic Sleep and thermoregulation

6. …cont. Cell bodies of PVN and SON are large and are said to be magno-cellular . Their axons project to the posterior pituitary. Their stimulation produces oxytocin (PVN) and ADH (SON) Cell bodies of the nuclei that control the adenohypophysis (collectively termed hypophysiotropic nuclei ) are small (parvicellular) . Their axons project to the median eminence Examples: pre-optic, arcuate , periventricular and ventromedial nuclei

7. Embryology Hypothalamus develops from the neuro-ectoderm Three swellings develop from the lateral walls of the third ventricles to form diencephalon. These swellings later develop to from epithalamus, thalamus and the hypothalamus The n euroblasts on the most ventral swelling proliferate to form the hypothalamus. Various nuclei develop later

8. …cont.

9. Blood supply and drainage From the posterior communicating artery- a branch of posterior cerebral- a branch of basilar artery Venous drainage is via internal cerebral veins into the great cerebral veins into the straight sinus. Also in to the hypophysial portal system

10. PITUITARY GLAND Small gland; 1cm in diameter; 0.5g-1g in weight Located in a depression called sella turcica found at the center of the sphenoid bone Covered on the superior surface by diaphragmatic sellae Related superiorly with the optic chiasm

11. …cont. Connected to the hypothalamus by the pituitary stalk or the infundibulum Microscopic examination reveals 2 types of tissue; epithelial and neuronal Epithelial portion makes up the adenohypophysis or anterior pituitary Neuronal portion makes up the posterior pituitary ( neurohypophysis )

12. …cont.

13. …cont.

14. Embryology Develops from 2 sources Neurohypophysis develops as an downward outgrowth of the floor of the diencephalon (infundibulum) Adenohypophysis develops from an invagination of the roof of the stomodium (Rathkes’s pouch) Infundibulum and rathkes pouch fuses to form the pituitary gland

15. NEUROHYPOPHYSIS Also called the posterior pituitary Divided into 3 parts: Pars nervosa-most caudal part and forms the posterior pituitary proper Infundibulum – this the connecting stalk between the hypothalamus and the pars nervosa Median eminence-most rostral part is continuous with the hypothalamus

16. …cont. Neuronal in origin. Made up of axons of neurons whose cell bodies are in the hypothalamus i.e. (SON and PVN) Pituicytes are the main supportive cells- these cells are glial in origin and resemble astrocytes SON and PVN synthesizes ADH and oxytocin respectively

17. …cont. They are then transported down the axon to be stored in the terminal buttons of these axons located in the pars nervosa Microcopy of the pars nervosa shows Herring’s bodies -axonal swellings due to storage of hormones ADH and or oxytocin hormones are released in response to an action potential that travels down from the cell body Posterior pituitary is reach in fenestrated capillary network

18. …cont.

19. ADENOHYPOPHYSIS Also called anterior pituitary It is divided into 3 parts; Pars distalis-90% of a denohypophysis Pars tuberalis-wraps around the stalk Pars intermedius- between the pars distalis and the neurohypophysis. It absent in adult humans.

20. …cont. Epithelial in origin Made up of five types of cells grouped into two main groups i.e.: Acidophils which include: Somatoptropes Lactotropes Basophils which include: Gonadotropes Corticoptropes Thyrotropes

21. …cont. Lactotropes produces prolactin hormone Corticotropes produces CRH Thyrotropes produces TSH Somatotropes produces GH Gonadotropes produces LH and FSH

22. …cont. These anterior pituitary cells have GPCR which when activated by the hypothalamic hormone causes a cascade of events that either stimulate or inhibit release of pituitary hormones

23. …cont.

24. …cont. Network of blood vessels run from the median eminence to supply the adenohypophysis These blood vessels are contained within the pituitary stalk (made of infundibulum and the pars tuberalis. They transport releasing or inhibiting hormones that have been produced by the hypothalamus into the adenohypophysis

25. Blood supply and drainage Arterial supply is from inferior and superior hypophysial arteries both being branches of the internal carotid Veins that drain the pituitary gland drain into cavernous sinus.

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