pituitary gland (1)

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PITUITARY GLAND (Hypophysis Cerebri)

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a small, oval(12mm.8mm) endocrine gland at the base of the brain attached to the hypothalamus by the infundibulum (pituitary stalk). The pituitary hormones control the function of most other endocrine glands (the master endocrine gland). THE PITUITARY GLAND

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located in the sella turcica, covered by the diaphragma sellae. ST: sella turcica CL: clivus OS: optic sulcus FO: foramen ovale FL: foramen lacerum PT: petrous temporal FM: foramen magnum

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Functionally, the pituitary is divided into two lobes that arise from different embryological sources: The pituitary gland Anterior lobe (adenohypophysis) Posterior lobe (neorohypophysis) Pars distalis (pars anterior) Pars tuberalis Pars intermedia (It is the upward extention of pars distalis along the stalk) Pars nervosa infundibulum

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Development of the pituitary Develops from Rathke’s pouch as an upward growth from the roof of the stomodeum. Develops from the infundibulum As a downward growth from the floor of the diencephalon. Anterior lobe Posterior lobe The pituitary gland is ectodermal in origin.

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Rathke’s pouch

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stomodeum

Relations of the pituitary gland : 

Relations of the pituitary gland

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Remember : The contents of the cavernous sinus : Internal carotid artery. Abducent nerve. Ophthalmic division of the trigeminal nerve. Maxillary division of the trigeminal nerve. Oculomotor nerve. Trochlear nerve.

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POSTERIOR PITUITARY GLAND HORMONES Oxytocin and Vasopressin are manufactured in the hypothalamus, but released in the posterior pituitary.

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ANTERIOR PITUITARY GLAND HORMONES GROWTH HORMONE (GH) – regulates growth; affects protein, fat and carbohydrate metabolism. THYROID STIMULATING HORMONE (TSH) – controls secretion of thyroxin. ADRENOCORTICOTROPIC HORMONE (ACTH) – controls secretion of hormones released by adrenal cortex. FOLLICLE-STIMULATING HORMONE (FSH) – in females, stimulates magturation of egg cells and estrogen secretion by ovaries. LUTENIZING HORMONE (LH) – in males, stimulates secretion of testosterone and sperm production by testes. In females, stimulates release of ovum by ovary. MELANOCYTE-STIMULATING HORMONE (MSH) – along with ACTH, affects pigment release in skin. PROLACTIN (PRL) – stimulates milk production.

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Note Pituitary Portal System!!

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Blood supply The arterial supply of the pituitary is derived from the superior and inferior hypophyseal arteries, which are branches of the internal carotid artery. The veins drain into the intercavernous sinuses.

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1, superior ophthalmic vein 2, anterior intercavernous sinus 3, inferior ophthalmic vein 4, pterygoid plexus 5, middle meningeal vein 6, superior petrosal sinus 7, inferior petrosal sinus 8, basilar venous plexus 9, transverse sinus 10, posterior intercavernous sinus 11, cavernous sinus 12, sphenoparietal sinus

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Pituitary tumors and the optic chiasma Enlargement of the pituitary gland causes it to expand superiorly because it is located in the bony sella turcica. A pituitary tumor pushes the diaphragma sellea upward and causes pressure on the optic chiasma. This interferes with the function of the nerve fibers crossing in the chiasma and the patient presents bitemporal hemianopia.

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Bitemporal hemianopia is a type of partial blindness where vision is missing in the outer (temporal) half of both the right and left visual field. It is usually associated with lesions of the optic chiasm near the pituitary gland.

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Transsphenoidal surgery

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Transsphenoidal surgery The pituitary is located at the base of the brain in the middle cranial fossa. To reach it and remove a tumor, the surgeon makes a small incision behind the upper lip or in the nose and is directed through the sphenoid bone and sphenoid air sinus. This is called transsphenoidal surgery. Most pituitary tumors are removed by this procedure.

Congenital anomalies of pituitary gland : 

Congenital anomalies of pituitary gland 1- Agenesis: Failure of formation. 2- Absent anterior lobe. 3- Pharyngeal hypophysis: pituitary gland remains attached to wall of pharynx.

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