{"id":4422247,"date":"2025-01-11T09:53:14","date_gmt":"2025-01-11T15:53:14","guid":{"rendered":"https:\/\/myendoconsult.com\/learn\/topics\/anatomy-of-the-pituitary-gland\/"},"modified":"2025-01-13T06:55:54","modified_gmt":"2025-01-13T12:55:54","slug":"anatomy-of-the-pituitary-gland","status":"publish","type":"oen_topic","link":"https:\/\/myendoconsult.com\/learn\/topics\/anatomy-of-the-pituitary-gland\/","title":{"rendered":"Anatomy of the Pituitary Gland"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">DEVELOPMENT OF THE PITUITARY GLAND<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Two Major Components<\/strong>\n<ol class=\"wp-block-list\">\n<li><strong>Adenohypophysis (Anterior Lobe)<\/strong>: Derived from <strong>oral ectoderm<\/strong>.<\/li>\n\n\n\n<li><strong>Neurohypophysis (Posterior Lobe)<\/strong>: Derived from <strong>neural ectoderm<\/strong> of the forebrain floor.<\/li>\n<\/ol>\n<\/li>\n\n\n\n<li><strong>Formation of Rathke Pouch (Weeks 4\u20135 of Gestation)<\/strong>\n<ul class=\"wp-block-list\">\n<li>A pouch-like recess in the ectodermal lining of the stomodeum (primitive mouth).<\/li>\n\n\n\n<li>Grows upward to meet the undersurface of the forebrain.<\/li>\n\n\n\n<li>The connection between Rathke pouch and the stomodeum (craniopharyngeal canal) is usually obliterated.<\/li>\n\n\n\n<li>A persistent remnant can become a \u201cpharyngeal pituitary,\u201d which may later give rise to ectopic hormone-secreting <a href=\"https:\/\/myendoconsult.com\/learn\/topics\/nonfunctioning-pituitary-adenoma\/\" data-wpil-monitor-id=\"83\">adenomas<\/a>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Infundibular (Neural) Outgrowth<\/strong>\n<ul class=\"wp-block-list\">\n<li>Develops from the floor of the third ventricle (neural ectoderm).<\/li>\n\n\n\n<li>Forms the <strong>infundibular process<\/strong>, which becomes solid except at its upper end (the infundibular recess of the third ventricle).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Fusion and Further Differentiation<\/strong>\n<ul class=\"wp-block-list\">\n<li>Rathke pouch fuses with the infundibular process.<\/li>\n\n\n\n<li>Lumen of Rathke pouch typically obliterates, but a <strong>Rathke cleft<\/strong> may persist.<\/li>\n\n\n\n<li><strong>Anterior Lobe (Pars Distalis)<\/strong> arises from Rathke pouch; <strong>Posterior Lobe (Pars Nervosa)<\/strong> arises from the infundibular process.<\/li>\n\n\n\n<li>The neurohypophysis (posterior lobe) contains axons (about 100,000 fibers) from the supraoptic and paraventricular nuclei of the hypothalamus.<\/li>\n\n\n\n<li>Remnants of Rathke pouch may persist at the boundary, forming small colloid cysts.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Pars Tuberalis, Pars Intermedia<\/strong>\n<ul class=\"wp-block-list\">\n<li>The <strong>pars tuberalis<\/strong> extends from the ventral wall of the anterior lobe and encircles the <a href=\"https:\/\/myendoconsult.com\/learn\/pituitary-stalk-thickening\/\" data-wpil-monitor-id=\"84\">pituitary stalk<\/a>.<\/li>\n\n\n\n<li>The <strong>pars intermedia<\/strong> is a thin region at the interface between the anterior and posterior lobes; in humans, it often becomes interspersed with anterior lobe cells but can produce POMC and ACTH.<\/li>\n\n\n\n<li>The <strong>median eminence<\/strong> is the part of the tuber cinereum lying immediately above the pars tuberalis.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1398\" height=\"887\" src=\"https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/pituitary-structure-mec-min.jpg\" alt=\"Anatomical components of the pituitary gland\" class=\"wp-image-733790\" srcset=\"https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/pituitary-structure-mec-min.jpg 1398w, https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/pituitary-structure-mec-min-300x190.jpg 300w, https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/pituitary-structure-mec-min-768x487.jpg 768w, https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/pituitary-structure-mec-min-624x396.jpg 624w\" sizes=\"auto, (max-width: 1398px) 100vw, 1398px\" \/><figcaption class=\"wp-element-caption\">The components of the hypophysis<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">DIVISIONS OF THE PITUITARY GLAND AND RELATIONSHIP TO THE HYPOTHALAMUS<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Adenohypophysis (Anterior Lobe)<\/strong>\n<ol class=\"wp-block-list\">\n<li><strong>Pars Tuberalis<\/strong>: Thin strip of tissue around the median eminence and upper neural stalk.<\/li>\n\n\n\n<li><strong>Pars Intermedia<\/strong>: Thin zone posterior to any persisting cleft, in contact with the posterior lobe.<\/li>\n\n\n\n<li><strong>Pars Distalis (Pars Glandularis)<\/strong>: Main secretory portion.<\/li>\n<\/ol>\n<\/li>\n\n\n\n<li><strong>Neurohypophysis (Posterior Lobe)<\/strong>\n<ol class=\"wp-block-list\">\n<li><strong>Infundibular Process<\/strong> (Neural Lobe)<\/li>\n\n\n\n<li><strong>Infundibular Stem<\/strong> (Neural Stalk)<\/li>\n\n\n\n<li><strong>Median Eminence<\/strong> (expanded upper end of the stalk\/tuber cinereum)<\/li>\n<\/ol>\n<\/li>\n\n\n\n<li><strong>Pituitary Stalk<\/strong>\n<ul class=\"wp-block-list\">\n<li>Formed by the <strong>infundibular stem<\/strong> plus surrounding parts of the adenohypophysis (pars tuberalis).<\/li>\n\n\n\n<li>Approximately 15% of the neurohypophysis extends up the stalk into the median eminence.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Nerve Supply (Hypothalamohypophysial Tract)<\/strong>\n<ul class=\"wp-block-list\">\n<li>Main functional\/anatomical supply of the neurohypophysis.<\/li>\n\n\n\n<li><strong>Supraopticohypophysial Tract<\/strong>: Arises in the supraoptic and paraventricular nuclei; runs in the anterior (ventral) wall of the stalk.<\/li>\n\n\n\n<li><strong>Tuberohypophysial Tract<\/strong>: Arises in the dorsal\/posterior hypothalamic regions, including paraventricular nucleus and tuberal\/mamillary areas.<\/li>\n\n\n\n<li>These fibers terminate mainly in the <strong>neurohypophysis<\/strong>.<\/li>\n\n\n\n<li>Damage above the median eminence affects ~85% of the supraoptic\/paraventricular neuron cell bodies; damage at the level of the diaphragma sellae affects ~70% of these cells.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Hypothalamic Boundaries<\/strong>\n<ul class=\"wp-block-list\">\n<li>Anteroinferiorly bounded by the optic chiasm\/tracts, posteriorly by the posterior perforated substance and cerebral peduncles, and separated from the thalamus by the hypothalamic sulcus.<\/li>\n\n\n\n<li>Merges anteriorly with preoptic septal region and posteriorly with the midbrain tegmentum.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Connective Tissue Trabecula<\/strong>\n<ul class=\"wp-block-list\">\n<li>Separates the anterior and posterior lobes internally for a variable distance, forming part of the vascular bed.<\/li>\n\n\n\n<li>The embryonic cleft (Rathke pouch remnant) may persist in this trabecula, more easily seen in newborns and often disappears with age.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/cavernous-sinus-illustration-update-1.jpg\" alt=\"\" class=\"wp-image-3302764\"\/><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">BLOOD SUPPLY OF THE PITUITARY GLAND<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Arterial Supply<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Superior Hypophysial Arteries<\/strong> (right and left) arise from the ophthalmic or internal carotid artery segment.\n<ul class=\"wp-block-list\">\n<li>Each divides into anterior and posterior branches to the pituitary stalk.<\/li>\n\n\n\n<li>Artery of the Trabecula: A branch supplying the connective tissue trabecula in the anterior lobe.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Inferior Hypophysial Arteries<\/strong> (right and left) branch from the intracavernous segment of each internal carotid artery.\n<ul class=\"wp-block-list\">\n<li>Surround the infundibular process with an arterial ring.<\/li>\n\n\n\n<li>Supply the posterior lobe and lower infundibular stem.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Hypophysial Portal System<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Primary Capillary Network<\/strong> in the median eminence and infundibular stem receives hypothalamic releasing and inhibiting hormones from nerve endings.<\/li>\n\n\n\n<li><strong>Long and Short Hypophysial Portal Veins<\/strong>:\n<ul class=\"wp-block-list\">\n<li>Convey blood (and hypothalamic hormones) from the primary capillary network to the <strong>secondary plexus<\/strong> of sinusoids in the anterior lobe (pars distalis).<\/li>\n\n\n\n<li>The anterior lobe has <strong>no direct arterial supply<\/strong>; it relies on these portal vessels.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Venous Drainage<\/strong> flows from the secondary plexus into dural sinuses around the pituitary, then into general circulation.<\/li>\n\n\n\n<li><strong>Occlusion<\/strong> of these portal vessels can lead to ischemic necrosis of the anterior pituitary.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1352\" height=\"767\" src=\"https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/pituitary-hypophyseal-vasculature-MEC.jpg\" alt=\"Venous and arterial supply of the pituitary gland. AH adenohypophysis, NH neurohypophysis\" class=\"wp-image-3075337\" srcset=\"https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/pituitary-hypophyseal-vasculature-MEC.jpg 1352w, https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/pituitary-hypophyseal-vasculature-MEC-300x170.jpg 300w, https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/pituitary-hypophyseal-vasculature-MEC-768x436.jpg 768w, https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/pituitary-hypophyseal-vasculature-MEC-624x354.jpg 624w\" sizes=\"auto, (max-width: 1352px) 100vw, 1352px\" \/><figcaption class=\"wp-element-caption\"> Venous and arterial supply of the pituitary gland. AH adenohypophysis, NH neurohypophysis<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">ANATOMY AND RELATIONSHIPS OF THE PITUITARY GLAND<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Size and Position<\/strong>\n<ul class=\"wp-block-list\">\n<li>Reddish-gray, ovoid organ measuring ~12 mm (transverse), 8 mm (AP), 6 mm (vertical).<\/li>\n\n\n\n<li>Weighs ~500 mg in men and ~600 mg in women.<\/li>\n\n\n\n<li>Sits in the <strong>hypophysial fossa<\/strong> of the sphenoid bone, beneath the <strong>diaphragma sellae<\/strong> (a dura mater fold).<\/li>\n\n\n\n<li>The floor of the hypophysial fossa is part of the roof of the sphenoid sinus.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Diaphragma Sellae<\/strong>\n<ul class=\"wp-block-list\">\n<li>Pierced by a small aperture for the pituitary stalk.<\/li>\n\n\n\n<li>Separates much of the pituitary gland from the <strong>optic chiasm<\/strong>.<\/li>\n\n\n\n<li>The subarachnoid space may extend partially into the sella (\u201cpartially empty sella\u201d) and can allow blood or CSF to enter this space.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Hypothalamus<\/strong>\n<ul class=\"wp-block-list\">\n<li>Lies superiorly, forming the floor and lateral walls of the <strong>third ventricle<\/strong>.<\/li>\n\n\n\n<li>Mamillary bodies mark the posterior limits of the hypothalamus.<\/li>\n\n\n\n<li>The optic chiasm lies just anterior\/superior to the pituitary stalk and diaphragma sellae.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Optic Chiasm<\/strong>\n<ul class=\"wp-block-list\">\n<li>A flat, quadrilateral bundle of optic nerve fibers at the junction of the anterior wall of the third ventricle with its floor.<\/li>\n\n\n\n<li>Rests on the diaphragma sellae behind the optic groove of the sphenoid bone.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong><a href=\"https:\/\/myendoconsult.com\/learn\/pineal-gland\/\" data-wpil-monitor-id=\"85\">Pineal Gland<\/a><\/strong>\n<ul class=\"wp-block-list\">\n<li>A small, conical gland lying below the splenium of the corpus callosum.<\/li>\n\n\n\n<li>Rarely, ectopic pineal tissue can be found near the floor of the third ventricle.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">RELATIONSHIP OF THE PITUITARY GLAND TO THE CAVERNOUS SINUS<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Cavernous Sinuses<\/strong>\n<ul class=\"wp-block-list\">\n<li>Dural venous channels flanking the pituitary gland on each side.<\/li>\n\n\n\n<li><strong>Reticulated Structure<\/strong>: Contains interlacing filaments around the internal carotid artery.<\/li>\n\n\n\n<li><strong>Medial Wall<\/strong>: Internal carotid artery, abducens nerve (VI).<\/li>\n\n\n\n<li><strong>Lateral Wall<\/strong>: Oculomotor (III), Trochlear (IV), and the ophthalmic and maxillary divisions of the trigeminal (V).<\/li>\n\n\n\n<li>The two cavernous sinuses communicate via anterior and posterior intercavernous sinuses, forming a circular sinus around the pituitary.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Superior and <a href=\"https:\/\/myendoconsult.com\/learn\/inferior-petrosal-sinus-sampling-ipss-testing-procedure-for-evaluating-cushings-syndrome\/\" data-wpil-monitor-id=\"86\">Inferior Petrosal Sinuses<\/a><\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Superior Petrosal Sinus<\/strong>: Connects cavernous sinus to the transverse sinus; runs in the attached margin of the tentorium cerebelli.<\/li>\n\n\n\n<li><strong>Inferior Petrosal Sinus<\/strong>: Also connects cavernous sinus to other posterior dural sinuses.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Internal Carotid Artery (Intercavernous Portion)<\/strong>\n<ul class=\"wp-block-list\">\n<li>Curves upward, forward, and then upward again through the cavernous sinus.<\/li>\n\n\n\n<li>Perforates the dura of the sinus roof near the anterior clinoid process.<\/li>\n\n\n\n<li>Surrounded by sympathetic fibers.<\/li>\n\n\n\n<li>Gives off <strong>hypophysial arteries<\/strong> to supply posterior lobe and median eminence (portal system).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">RELATIONSHIPS OF THE SELLA TURCICA<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Location and Dimensions<\/strong>\n<ul class=\"wp-block-list\">\n<li>A deep depression in the <strong>body of the sphenoid bone<\/strong>.<\/li>\n\n\n\n<li>Normal adult dimensions:\n<ul class=\"wp-block-list\">\n<li>AP length &lt;14 mm<\/li>\n\n\n\n<li>Height &lt;12 mm (floor to a line from tuberculum sellae to posterior clinoid tip)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Sphenoid Bone Overview<\/strong>\n<ul class=\"wp-block-list\">\n<li>Composed of a median body and two pairs of wings (greater and lesser), plus two pterygoid processes.<\/li>\n\n\n\n<li><strong>Sphenoidal Air Sinuses<\/strong>: Large cavities within the body, separated by a septum (often oblique).<\/li>\n\n\n\n<li>Superior surface articulates with the ethmoid and frontal bones; houses grooves for the olfactory bulbs, and the <strong>chiasmatic sulcus<\/strong> for the optic chiasm.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Key Features<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Tuberculum Sellae<\/strong>: A raised area behind the chiasmatic sulcus.<\/li>\n\n\n\n<li><strong>Dorsum Sellae<\/strong>: Posterior boundary of the sella turcica, ending in the posterior clinoid processes.<\/li>\n\n\n\n<li><strong>Hypophysial Fossa<\/strong>: Deepest part, housing the pituitary gland.<\/li>\n\n\n\n<li><strong>Clivus<\/strong>: A shallow depression behind the dorsum sellae, leading to the basilar part of the occipital bone.<\/li>\n\n\n\n<li>Lateral aspects relate to the <strong>cavernous sinus<\/strong> and the foramen lacerum region.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Nasal Relations<\/strong>\n<ul class=\"wp-block-list\">\n<li>The crest of the sphenoid bone and the perpendicular plate of the ethmoid.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Surgical Considerations<\/strong>\n<ul class=\"wp-block-list\">\n<li>Modern pituitary approaches (microscopic or endoscopic) aim to avoid major vascular structures and the optic pathways.<\/li>\n\n\n\n<li>Transsphenoidal surgery exploits the sphenoidal sinus route to access the sella turcica.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>DEVELOPMENT OF THE PITUITARY GLAND DIVISIONS OF THE PITUITARY GLAND AND RELATIONSHIP TO THE HYPOTHALAMUS BLOOD SUPPLY OF THE PITUITARY GLAND ANATOMY AND RELATIONSHIPS&hellip;<\/p>\n","protected":false},"featured_media":0,"template":"","oen_topic_chapter":[682],"class_list":["post-4422247","oen_topic","type-oen_topic","status-publish","hentry","oen_topic_chapter-pituitary-gland"],"_links":{"self":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422247","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic"}],"about":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/types\/oen_topic"}],"version-history":[{"count":6,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422247\/revisions"}],"predecessor-version":[{"id":4422313,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422247\/revisions\/4422313"}],"wp:attachment":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/media?parent=4422247"}],"wp:term":[{"taxonomy":"oen_topic_chapter","embeddable":true,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic_chapter?post=4422247"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}