University:
Kentucky State University
Course:
BIO 301 | Human Anatomy
Academic year:

2021
Views:

231

Pages:

48
Author:

Tyshawn Shaffer

Objectives 1. Recognize and understand the main parts of the pituitary gland and their locations, relations and connections. 2. Comprehend the blood supply of the pituitary gland and its portal circulation. Understand the embryological origins of the pituitary gland. 3. 4. Grasp the clinical correlations of the pituitary gland on anatomical basis and its surgical approach. 5. Recognize and understand imaging of the pituitary gland. 6. Grasp the histological structure of the pituitary gland and its cells under light and electron microscopes. 7. Recognize and understand the location, simple structure of the hypothalamus and its connections The hypothalamus  consists of only 4 cm, 0.3% of the total brain shatarat  It lies beneath the thalamus  It contains the integrative systems that, via the autonomic and endocrine effector systems, control fluid and electrolyte balance, food ingestion and energy balance, reproduction, thermoregulation, and immune and many emotional responses The hypothalamus contains a number of neuronal groups called nuclei A-Through neurosecretory projections to the posterior pituitary B-Through neurosecretory projections to the median eminence (these control the endocrine output of the anterior pituitary and thereby the peripheral endocrine organs) THE PITUITARY GLAND also known as the HYPOPHYSIS Master organ???? The pituitary It is a pea-sized Weighs 0.5 g in males and 1.5 g in multiparous women It is centrally located at the base of the brain, where it lies in a saddle-shaped depression of the sphenoid bone called THE SELLA TURCICA A short stalk, the infundibulum connects the pituitary gland to the hypothalamus.  A circular fold of dura mater, the diaphragma sellae forms the roof of this fossa  The diaphragma sellae is pierced by a small central aperture through which the pituitary stalk passes, and it separates the anterior part of the upper surface of the gland from The optic chiasma.  The hypophysis is bound on each side by The cavernous sinuses and the structures that they contain. The cavernous sinuses Cranial nerve number (3) oculomotor nerve Cranial nerve number (4) Trochlear nerve Divisions of Cranial nerve number (5) trigeminal nerve Ophthalmic nerve Maxillary nerve How about the mandibular nerve? The internal carotid artery The cranial nerve number (6) abducent nerve  it is separated from the floor of the fossa by a large, partially vacuolated venous sinus endoscopic transnasal applications in many pituitary surgical centers!!!!! THE SELLA TURCICA (hypophyseal fossa) The pituitary The pituitary gland is composed of two functional tissues Neural (secretory) tissue Posterior lobe (Neurohypophysis) Glandular epithelial tissue The Anterior lobe (Adenohypophysis) Each endocrine gland has two different Embryological origins The two portions are of different embryologic origin The anterior lobe of the pituitary gland is derived from an evagination of the ectoderm of the oropharynx toward the brain Rathke’s pouch The posterior lobe of the pituitaryis derived from a downgrowth (the future infundibulum) neuroectoderm of the ﬂoor of the third ventricle (the diencephalon) of the developing brain The anterior lobe of the pituitary gland consists of three derivatives of Rathke’s pouch: 1-Pars distalis which comprises the bulk of the anterior lobe of the pituitary gland and arises from the thickened anterior wall of the pouch It is not part of the pituitary gland The median eminence is part of the hypothalamus from which regulatory hormones are released 3-Pars tuberalis which develops from the thickened lateral walls of the pouch and forms a sheath around the infundibulum The embryonic infundibulum gives rise to the posterior lobe of the pituitary gland Infundibulum, which is continuous with the median eminence and contains the neurosecretory axons forming the hypothalamohypophyseal tracts The posterior lobe consists of the following: •Pars nervosa, which contains neurosecretory axons and their endings shatarat Hypophysial arteries are branches of the intercavernous segment of The internal carotid artery The inferior branch supplies the posterior lobe of the pituitary gland The superior branch leads into the median eminence to start the hypophysial portal system to the anterior lobe A-Superior hypophyseal arteries These vessels arise from the internal carotid arteries and posterior communicating artery of the circle of Willis They supply The pars tuberalis Median eminence Infundibulum Divides into medial and lateral arteries Form an arterial ring around the infundibulum Inferior hypophyseal An important functional observation is that most of the anterior lobe of the pituitary gland has no direct arterial supply!!!!! A Portal System artery WHAT IS A Portal System? Usually, blood passes from the heart through an artery to a capillary to a vein and back to the heart.  In a portal system, blood flows from one capillary network into a portal vein, and then into a second capillary network before returning to the heart. The name of the portal system indicates the location of the second capillary network. The hypothalamohypophyseal portal system provides the crucial link between the hypothalamus and the pituitary gland. Superior hypophyseal arteries give rise to fenestrated capillaries (the primary capillary plexus). drain intohypophyseal portal veins They run along the pars tuberalis give rise to a second fenestrated sinusoidal capillary network (the secondary capillary plexus) shatarat B-Inferior hypophyseal arteries The inferior hypophysial vessels arise solely from the internal carotid arteries primarily supply the pars nervosa Most of the blood from the pituitary gland drains into the cavernous sinus and then into the systemic circulation. The posterior pituitary Neurohypophysis is neural tissue and is formed by the distal axons of The supraoptic nucleus (SON) and The paraventricular nucleus (PVN) of the hypothalamus. shatarat The pituitary gland enlarges during pregnancy (primarily because of lactotroph hyperplasia) portal venous blood supply is uniquely vulnerable to changes in arterial blood pressure severe postpartum uterine hemorrhage, spasm of the infundibular arteries, which are drained by the hypophysial portal vessels,. could result in pituitary infarction. If the lack of blood flow continued for several hours, most of the tissues of the anterior pituitary gland infarcted; when blood finally started to flow, stasis and thrombosis occurred in the stalk and the adenohypophysis Mass effects Pituitary Adenoma The optic chiasm lies above the diaphragma sellae. The most common sign that a pituitary tumor has extended beyond the confines of the sella turcica is a visual defect caused by the growth pressing on the optic chiasm.. The most frequent disturbance is a Bitemporal hemianopsia Bitemporal hemianopsia A city as seen with bitemporal hemianopsia. is the most common tumor found in the region of the pituitary gland in children and adolescents and constitutes about 3% of all intracranial tumors and up to 10% of all childhood brain tumors. Craniopharyngiomas histologically benign epithelioid tumors arising from embryonic squamous remnants of Rathke pouch—may be large (e.g., > 6 cm in diameter) and invade the third ventricle and associated brain structures. shatarat sellar Make sure you understand the presence of region and the fact that Suprasellar manifestations are usually related to hypothalamus While intrasellar could be from the anterior or posterior lobe of the pituitary gland CENTRAL DIABETES INSIPIDUS Tumor Other causes Reabsorption of water in cortical and medullary collecting ducts lost in absence of ADH shatarat acute hemorrhage of the pituitary gland The typical presentation is acute onset of severe headache (frequently described as “the worst headache of my life”) vision loss (the hemorrhagic expansion takes the path of least resistance and extends superiorly and compresses the optic chiasm); ocular nerve palsies (e.g., ptosis, diplopia) caused by impingement of the third, fourth, and sixth cranial nerves in the cavernous sinuses

Main Parts of the Pituitary Gland

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