Pituitary Gland

Dr: Azza Zaki

Pituitary Gland (Hypophysis Cerebri) It is the master endocrine gland, because it controls the other endocrine glands & body growth.  It is attached to the under-surface of the brain (hypothalamus) by the infundibulum (stalk). Dr: Azza Zaki

Pituitary Gland Location: Small, slightly oval gland lies in the hypophyseal fossa (sella turcica) of the sphenoid bone. It is covered by an extension of the dura matter, diaphragma sellae. Dr: Azza Zaki

Relations Superiorly: The diaphragma sellae, which separates the gland from the optic chiasma. Laterally: cavernous sinus &its contents. Inferiorly: body of the sphenoid and sphenoidal sinus separating the gland from nasopharynx. Dr: Azza Zaki

Relations Anteriorly: Tuberculum sellae Sphenoidal sinus The nasal cavity. Posteriorly: Dorsum sellae Basilar artery. The pons Dr: Azza Zaki

Development Of The Pituitary Gland

The pituitary gland is ectodermal in origin, develops from 2 sources: Anterior lobe or adenohypophysis: it arises from a small ectodermal diverticulum (Rathke’s pouch) grows from the roof of the stomodeum (mouth). Posterior lobe or neurohypophysis: a small ectodermal diverticulum (the infundibulum) which grows from the floor of the diencephalon. Dr: Azza Zaki

Lobes Of The Pituitary Gland

Dr: Azza Zaki

Hypophysis cerebri actually consists of 2 glands that are united anatomically but functions differently.

Adenohypophysis

Neurohypophysis

Infundibulum

Pars Nervosa Pars Intermedia Dr: Azza Zaki

Pars Distalis (anterior lobe)

Pars Tuberalis

Lobes Of The Pituitary Gland The pituitary gland is divided into: An anterior lobe, or adenohypophysis: is subdivided into: the pars anterior (pars distalis), the pars intermedia, which may be separated by a cleft (remnant of an embryonic pouch) The pars tuberalis A posterior lobe or neurohypophysis: pars nervosa & stalk Dr: Azza Zaki

Blood Supply Arterial supply: from superior &inferior hypophyseal branches of the internal carotid artery. Venous drainage: cavernous and intercavernous sinuses. Receives venous blood from hypothalamus via hypothalamo-hypophyseal portal venous system which transmits releasing factors to the anterior lobe of the pituitary gland to control the Dr: Azza Zaki release of its hormones.

Control Of The Pituitary Gland

Nervous

Vascular

Hypothalamohypophyseal tract to posterior lobe

Hypothalamo hypophyseal portal system to anterior lobe

Dr: Azza Zaki

Connections Of The Hypothalamus With The Hypophysis Cerebri The hypothalamus is connected to the pituitary gland by: Hypothalamohypophyseal tract: nerve fibers that travel from the supraoptic & paraventricular nuclei to the posterior lobe of the hypophysis. Hypophyseal portal system: long & short portal blood vessels that connect sinusoids in the median eminence& infundibulum with capillary plexuses in the anterior lobe of Dr: Azza Zaki the hypophysis

Hypothalamohypophyseal Tract The hormones vasopressin (antidiuretic ADH)& oxytocin are synthesized in the supraoptic & paraventricular nuclei. The hormones are passed along the axons of the hypothalamophypophyseal tract & are released at the axon terminals, into the blood stream in capillaries of the posterior pituitary. Oxytocin stimulates: the contraction of the uterus & myoepithelial cells of the ducts Dr: Azza Zaki of the breast

Hormones of the Posterior Pituitary

Dr: Azza Zaki

hypothalamo-hypophyseal portal venous system The portal system carry releasing hormones and release – inhibiting hormones from hypothalamus to anterior lobe of pituitary. Dr: Azza Zaki

hypothalamo-hypophyseal portal system The Superior hypophyseal arteries arise from the internal carotid arteries, supply the median eminence, the infundibulum and adjacent parts of the anterior lobe. form a primary capillary plexus that irrigate infundibulum and the median eminence. Rejoins to form hypophyseal veins that develops a secondary capillary plexus (sinusoids) that pass between the secretory cells of the Dr: Azza Zaki anterior lobe.

Hypothalamo- hypophyseal portal system

Dr: Azza Zaki

Dr: Azza Zaki

Hormones of the Anterior Pituitary

Dr: Azza Zaki

Slide 9.17

The Hormones Of The Anterior Pituitary ACTH: adrenocorticotropic hormone: stimulate adrenal cortex FSH: follicle stimulating hormone: stimulates growth of follicles in the ovary & spermatogenesis in the testis. LH: luteinizing hormone: stimulates secretion of estrogen & progesterone & ovulation (in female) Interstitial cell stimulating hormone (ICSH): stimulate release of testosterone (in male). TSH: thyrotropic hormone or thyroid stimulating hormone. GH: growth hormone: stimulate the body growth MSH: melanocyte- stimulating hormone Prolactin (LTH): luteotropic hormone (lactogenic hormone: stimulates milk secretion by mammary gland during lactation Dr: Azza Zaki

Clinical Notes

Dr: Azza Zaki

Pituitary Enlargement (Tumor) And The Optic Chiasm Since the pituitary is located in the bony sella turcica, enlargement causes it to expand superiorly. A pituitary tumor classically pushes the diaphragma sellae upward and causes pressure on the optic chiasma. This results in interference with the function of the nerve fibers crossing in the chiasma (from the inner quadrants of the retina), and the patient presents with bitemporal hemianopia is a loss of the lateral halves of the fields of vision of both eyes (loss of function of the medial half of both retinas). Further expansion of the pituitary tumor causes erosion of the body of the sphenoid bone (x-ray: ballooning of the sella turcica). Dr: Azza Zaki Dr: Azza Zaki

Sella turcica

Dr: Azza Zaki

Surgical Approach Trans-cranial (subfrontal approach): the gland can be approached through the anterior cranial fossa by elevating the frontal lobe of the brain . Trans-sphenoidal approach: entering the pituitary fossa through the sphenoidal air sinus .

Dr: Azza Zaki

Dwarfism A deficiency in the growth hormone secreted by the somatotrope cells of the pars anterior during childhood leads to pituitary dwarfism. Growth does not stop entirely, and the different parts of the body are in relatively normal proportions. The person is of normal intelligence, but the facial skin is Dr: Azza Zaki often wrinkled and sexual

Gigantism and Acromegaly Excessive production of the growth hormone by the somatotrope cells of the pars anterior or by tumors of these cells can produce abnormal growth of the skeleton. Gigantism occurs in the young before the epiphyses in long bones fuse with the diaphysis. Acromegaly is a form of abnormal skeletal and soft tissue growth that occurs after adolescence, following the fusion of the epiphyses in long bones with the diaphysis. In this disease, the individual cannot grow taller, but overgrowth occurs in the bones and soft tissues of the forehead, nose, lower jaw, hands, and feet. Dr: Azza Zaki

Diabetes Insipidus This syndrome results from a lesion of the supraoptic and paraventricular nuclei of the hypothalamus and a failure of these cells to synthesize the antidiuretic hormone, or from destruction of the hypothalamohypophysial tract.  There are many causes of this syndrome, including cerebral tumors, cerebral abscesses, surgical or radiation damage, and head injuries. Characteristically, the patient passes large volumes of urine (polyuria) of low specific gravity. As a result, the patient is extremely thirsty

Dr: Azza Zaki

Dr: Azza Zaki