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Anatomy of Pituitary
- 1. SAKRA INSTITUTE OF NEUROSCIENCES Pituitary stalk anatomy Dr Abhishek Rai DNB Neurosurgery
- 2. SAKRA INSTITUTE OF NEUROSCIENCES Title 1. Introduction 2. Embryogenesis 3. Histogenesis 4. Gross anatomy 5. Vascular supply 6. Surgical anatomy 7. Clinical aspect
- 3. SAKRA INSTITUTE OF NEUROSCIENCES Introduction • Also known as Hypophysis cerebri. • 1909, Harvey Cushing pondered its dispensability in a treatise entitled, ‘‘Is the pituitary gland essential to the maintenance of life?’’
- 4. SAKRA INSTITUTE OF NEUROSCIENCES Embryogenesis • Rathke’s pouch, a dorsal evagination of the stomodeum immediately anterior to the buccopharyngeal membrane, and the infundibulum, a ventral extension of the diencephalon just caudal to the optic chiasm. • Another dorsal evagination of the stomodeum, the pouch of Sessel, arises just posterior to the buccopharyngeal membrane. sometimes persists in human beings and can be the source of certain tumors. • Rathke’s pouch and the infundibulum are both derivatives of the ectodermal germ cell layer, but they ultimately generate distinct histologic patterns.
- 5. SAKRA INSTITUTE OF NEUROSCIENCES Embryogenesis
- 6. SAKRA INSTITUTE OF NEUROSCIENCES
- 7. SAKRA INSTITUTE OF NEUROSCIENCES Histogenesis • By the 3rd and 4th months of gestation, cells of the anterior lobe arrange themselves as cords around blood sinusoids. Glandular organization is induced by the surrounding mesenchyme. • Simultaneously, the portal system of blood vessels develops and is fully established by the end of the first trimester. • Anterior lobe cells further differentiate into histologically discrete populations characterized by the affinity of their cytoplasm for selected dyes (acidophils, basophils, and chromophobes). • The relative density of these cells comports with the bilateral symmetry achieved during morphogenesis of the adenohypophysis. • Basophilic cells are concentrated in the pars medialis. Conversely, acidophils tend to be distributed in the pars lateralis.
- 8. SAKRA INSTITUTE OF NEUROSCIENCES Histogenesis • The adenohypophysis begins to function during the first trimester. Corticotropin, b-endorphin, luteinizing hormone (LH), and follicle stimulating hormone (FSH) can all be detected early in gestation. • Thyrotropin-releasing hormone (TRH)– secreting cells develop early in the second trimester. • Growth hormone (GH) and prolactin (PRL) become increasingly synthesized during the second half of pregnancy.
- 9. SAKRA INSTITUTE OF NEUROSCIENCES Gross anatomy
- 10. SAKRA INSTITUTE OF NEUROSCIENCES Gross anatomy • The pituitary gland at birth is 100 mg. • Rapid growth occurs in childhood, followed by slower growth until the adult weight (approximately 500–600 mg) is attained in the latter part of the second decade. • The adult hypophysis measures approximately 10 mm in length, 10 to 15 mm in width, and about 5 mm in height. • On average, the female gland is almost 20% heavier than the male gland primarily because of relative differences in the size of the pars distalis. • 12% to 100% increase during pregnancy because of enlargement of the pars distalis.
- 11. SAKRA INSTITUTE OF NEUROSCIENCES Vascular anatomy • The anterior pituitary is the most richly vascularized of all mammalian tissues, receiving about 0.8 mL/g/min of blood from the portal system. • The pituitary gland derives its blood supply from two groups of arteries: • The superior hypophyseal artery (SHA) • The inferior hypophyseal artery (IHA)
- 12. SAKRA INSTITUTE OF NEUROSCIENCES Vascular anatomy
- 13. SAKRA INSTITUTE OF NEUROSCIENCES Vascular anatomy
- 14. SAKRA INSTITUTE OF NEUROSCIENCES Surgical anatomy • The pituitary gland is situated within the hypophyseal fossa, a fibro-osseous compartment near the center of the cranial base. • This fossa is demarcated laterally and superiorly by reflections of dura and elsewhere by the sella turcica, a depression in the body of the sphenoid bone.
- 15. SAKRA INSTITUTE OF NEUROSCIENCES Surgical anatomy
- 16. SAKRA INSTITUTE OF NEUROSCIENCES
- 17. SAKRA INSTITUTE OF NEUROSCIENCES
- 18. SAKRA INSTITUTE OF NEUROSCIENCES Surgical anatomy of the pituitary gland
- 19. SAKRA INSTITUTE OF NEUROSCIENCES Surgical anatomy of the pituitary gland
- 20. SAKRA INSTITUTE OF NEUROSCIENCES
- 21. SAKRA INSTITUTE OF NEUROSCIENCES Surgical anatomy of the pituitary gland
- 22. SAKRA INSTITUTE OF NEUROSCIENCES Physiology of the anterior lobe
- 23. SAKRA INSTITUTE OF NEUROSCIENCES Surgical anatomy of the pituitary gland
- 24. SAKRA INSTITUTE OF NEUROSCIENCES Clinical pespective • Pituitary stalk interruption syndrome
- 25. SAKRA INSTITUTE OF NEUROSCIENCES Clinical features 1. Headache 2. DI 3. SIADH 4. unilateral visual loss 5. homonymous hemianopsias 6. Growth failure 7. Lack of secondary sexual development 8. Hypothalamic Dysfunction
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Notes de l'éditeur
- The pituitary stalk, which connects the hypothalamus to the pituitary gland, carries both blood vessels and nerve fibres. The anterior pituitary is connected to the hypothalamus by a vascular connection through the hypophyseal portal system. The posterior pituitary consists of fibres of the magnocellular and parvocellular neurons, which carry the posterior pituitary hormones from the hypothalamus.
- The pituitary gland or hypophysis cerebri, derived from Greek terminology for its location as an attachment beneath the brain, was named by Andreas Vesalius in accordance with Aristotle’s belief that the pituitary was the organ through which phlegm, one of the body’s four essential. humors, passed from the brain
- It is now clear that the secretion of prolactin by the pituitary is continued or even enhanced by the removal of hypothalamic connections [Desclin, 1950; Everett, 1954], somatotroph are unable to function. The immediate effect of the operation on the anterior lobe (pars distalis) is the production of an extensive infarct in the central region, due to the severance of the long portal vessels of the stalk which supply the territory. The surviving parts of pars distalis are kept alive in certain areas by the short portal vessels. Since after stalk section, the central part of the gland is destroyed by an infarct, and the peripheral part (including the sex zone) survives it might be expected that gonadotrophic activity would be relatively less affected than thyrotrophic activity. But pituitary of the rat [Purves and Griesbach, 1951; Halmi, 1952 b; Swettenham, 1960], proved otherwise
- there exists a rough correlation between body length and the weight of the gland, these differences are also a result of variability in the pars distalis, because the size of the pars nervosa remains relatively constant. The volume of the pituitary gland decreases with aging
- Neural regulation of pituitary function occurs via two general mechanisms, each contingent on a distinct vascular network: direct projections of the hypothalamus to the neurohypophysis consisting of axon terminals that terminate in the posterior lobe and release their neurosecretory products directly into the bloodstream and regulation of the adenohypophysis via tropic hormones produced in the hypothalamus and conveyed to the anterior lobe via the portal venous system.
- The SHAs usually consist of a series of small vessels exiting the inferior medial portion of the ICA underneath the optic nerve. They supply the pituitary stalk, adenohypophysis, and inferior surface of the optic nerve and chiasm.
- HPA forms microcirculation at the base of the brain, connecting the hypothalamus with the anterior pituitary. Its main function is to quickly transport and exchange hormones between the hypothalamus arcuate nucleus and anterior pituitary gland. The capillaries in the portal system are fenestrated (have many small channels with high vascular permeability) which allows a rapid exchange between the hypothalamus and the pituitary. The main hormones transported by the system include gonadotropin-releasing hormone, corticotropin-releasing hormone, growth hormone–releasing hormone, and thyrotropin-releasing hormone.
- The chiasmatic groove (sulcus), a shallow depression between the optic foramina, is bounded posteriorly by the tuberculum sellae and anteriorly by the planum sphenoidale.
- The olfactory tracts, gyrus rectus, and posterior part of the frontal lobe rest against the smooth upper surface of the lesser wing; the temporal lobe rests against the inner surface of the greater wing; the pons and mesencephalon lie posterior to the clival portion; the optic chiasm lies posterior to the chiasmatic sulcus; and the IInd through VIth cranial nerves are intimately related to the sphenoid bone and all exit the cranium through the optic canal, superior orbital fissure, foramen rotundum, or foramen ovale, all foramina located in the sphenoid bone. The sphenoid bone has many important arterial and venous relationships: the carotid arteries groove each side of the sphenoid bone and often form a serpiginous prominence in the lateral wall of the sphenoid sinus, the basilar artery rests against its posterior surface, the circle of Willis is located above its central portion, and the middle cerebral artery courses parallel to the sphenoid ridge of the lesser wing. The cavernous sinuses rest against the sphenoid bone, and intercavernous venous connections line the walls of the pituitary fossa and dorsum sellae. Foramen rotandum: The maxillary nerve, artery of foramen rotundum, and emissary veins. Foramen Ovale: mandibular nerve ,accessory meningeal artery and lesser petrosal nerve
- In the anterior view, the sphenoid bone resembles a bat with wings outstretched. Central portion called the body; two lesser wings, which spread outward from the superolateral part of the body; two greater wings, which spread upward from the lower part of the body; and two pterygoid processes with their medial and lateral pterygoid plates directed downward from the body
- AIS: anterior intercavernous sinus; BS: basilar sinus; DSS: dorsum sellae sinus; H: hypophysis; IIS: inferior intercavernous sinus. In the superior view, the pituitary fossa occupies the central part of the body and is bounded anteriorly by the tuberculum sellae and posteriorly by the dorsum sellae
- The oculomotor nerve, trochlear nerve, and first two divisions of the trigeminal nerve are embedded in the lateral wall of the cavernous sinus, lying between the endothelial lining and the dura mater, whereas the abducens nerve is contained within the sinus itself.
- pituitary stalk transection syndrome, is a syndrome characterized by an absent or hypoplastic anterior pituitary gland, thin or absent infundibulum, and ectopic posterior pituitary location.
- meningitis or raised intracranial pressure are likely causes of headache in these patients.