{"id":4422379,"date":"2025-01-11T15:44:25","date_gmt":"2025-01-11T21:44:25","guid":{"rendered":"https:\/\/myendoconsult.com\/learn\/topics\/adrenal-gland-anatomy\/"},"modified":"2025-01-12T18:27:20","modified_gmt":"2025-01-13T00:27:20","slug":"adrenal-gland-anatomy","status":"publish","type":"oen_topic","link":"https:\/\/myendoconsult.com\/learn\/topics\/adrenal-gland-anatomy\/","title":{"rendered":"Adrenal Gland Anatomy"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">DEVELOPMENT OF THE ADRENAL GLANDS<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Historical Note<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>First detailed anatomic description<\/strong> by Bartholomeo Eustacius in 1563.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Overview<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Each adrenal gland consists of:\n<ul class=\"wp-block-list\">\n<li><strong>Cortex<\/strong>: Derived from <strong>mesenchymal tissue<\/strong>.<\/li>\n\n\n\n<li><strong>Medulla<\/strong>: Derived from <strong>ectodermal neural crest<\/strong> tissue.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>Both parts are enveloped in a <strong>common capsule<\/strong>.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Cortical Development<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Early Embryogenesis (5th\u20136th Week)<\/strong>\n<ul class=\"wp-block-list\">\n<li>Proliferation of <strong>mesenchymal (coelomic)<\/strong> cells adjacent to the urogenital ridge \u2192 <strong>primitive cortex<\/strong>.<\/li>\n\n\n\n<li>These cells penetrate retroperitoneal mesenchyme and form a fetal cortical mass.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Permanent <a href=\"https:\/\/myendoconsult.com\/learn\/the-formation-and-structure-of-the-adrenal-cortex\/\" data-wpil-monitor-id=\"150\">Cortex Formation<\/a><\/strong>\n<ul class=\"wp-block-list\">\n<li>Soon after the primitive cortex forms, a thin outer layer of cells (from the same mesodermal source) envelops it \u2192 <strong>permanent cortex<\/strong>.<\/li>\n\n\n\n<li>By the <strong>8th week<\/strong>, the forming cortex is in intimate contact with the <strong>cranial pole of the kidney<\/strong> and invests in a connective tissue capsule.<\/li>\n\n\n\n<li>This early adrenal is very large compared to the kidney.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Fetal vs. Permanent Cortex<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Fetal (Primitive) Cortex<\/strong>: Major bulk of the gland at birth; rapidly involutes after birth.\n<ul class=\"wp-block-list\">\n<li>By 2 weeks postpartum, the glands lose ~1\/3 of their weight.<\/li>\n\n\n\n<li>The fetal cortex fully disappears by the end of the first year.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Permanent (Outer) Cortex<\/strong>: Thin at birth; differentiates further once fetal cortex involutes.\n<ul class=\"wp-block-list\">\n<li>Full zonal differentiation (glomerulosa, fasciculata, reticularis) completes around the <strong>3rd year of life<\/strong>.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Role of Transcription Factors<\/strong>\n<ul class=\"wp-block-list\">\n<li>Differentiation dependent on temporal expression of genes (e.g., <strong>steroidogenic factor 1<\/strong>, <strong>zona glomerulosa\u2013specific protein<\/strong>, <strong>inner zone antigen<\/strong>).<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\">Medullary Development<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Neural Crest Origin<\/strong>\n<ul class=\"wp-block-list\">\n<li>Ectodermal cells from neural crest migrate to form <strong>sympathetic neurons<\/strong> (autonomic system).<\/li>\n\n\n\n<li>Some neural crest cells differentiate into <strong>chromaffin cells<\/strong> instead of neurons.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Chromaffin Cells<\/strong>\n<ul class=\"wp-block-list\">\n<li>Named for their brown staining with chromium salts (oxidation of catecholamines).<\/li>\n\n\n\n<li>Migrate from <strong>primitive autonomic ganglia<\/strong> adjacent to the developing cortex into the adrenal to form the <strong>medulla<\/strong> (7th week onward).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Paraganglia and Organ of Zuckerkandl<\/strong>\n<ul class=\"wp-block-list\">\n<li>Some chromaffin cells remain outside the adrenals \u2192 <strong>paraganglia<\/strong> along the aorta.<\/li>\n\n\n\n<li><strong>Organ of Zuckerkandl<\/strong>: A large paraganglion near the inferior mesenteric artery; prominent in fetuses, a key extra-adrenal catecholamine source in infancy.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\">Accessory and Absent Glands<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>True Accessory Adrenal Glands<\/strong> (cortex + medulla) are rare; can be found in celiac plexus or kidney cortex.<\/li>\n\n\n\n<li><strong>Adrenal \u201cRests\u201d<\/strong> (usually cortical only) may occur near the main gland or in retroperitoneum, spleen, etc.<\/li>\n\n\n\n<li><strong>Gonadal Proximity<\/strong> during embryonic life \u2192 ectopic adrenal tissue may appear in the <strong>spermatic cord, scrotum, ovary, or broad ligament<\/strong>.<\/li>\n\n\n\n<li><strong>Absent Adrenal Gland<\/strong> on one side can occur but <strong>bilateral absence<\/strong> is extremely rare.<\/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\">ANATOMY AND BLOOD SUPPLY OF THE ADRENAL GLANDS<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Location and Gross Anatomy<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Retroperitoneal<\/strong>\n<ul class=\"wp-block-list\">\n<li>At the <strong>upper poles of the kidneys<\/strong>.<\/li>\n\n\n\n<li>Level of ~T11 rib to L1 vertebra; each weighs ~3.5\u20136 g.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Capsule and Appearance<\/strong>\n<ul class=\"wp-block-list\">\n<li>Surrounded by <strong>areolar (fatty) tissue<\/strong>; covered by a thin fibrous capsule.<\/li>\n\n\n\n<li><strong>Golden-yellow<\/strong> cortical tissue on section; <strong>reddish-brown<\/strong> medullary center.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Right Adrenal Gland<\/strong>\n<ul class=\"wp-block-list\">\n<li>Triangular (\u201cpyramidal\u201d) shape.<\/li>\n\n\n\n<li>Higher and more lateral; close to right diaphragmatic crus.<\/li>\n\n\n\n<li>Surrounded by liver (anterosuperiorly), IVC (medially), upper pole of the right kidney (inferolaterally).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Left Adrenal Gland<\/strong>\n<ul class=\"wp-block-list\">\n<li>Elongated or semilunar shape, slightly larger.<\/li>\n\n\n\n<li>Often overlaps the lateral border of the aorta.<\/li>\n\n\n\n<li>Posterior surface adjacent to diaphragm, splanchnic nerves.<\/li>\n\n\n\n<li>Upper 2\/3 behind lesser sac; lower 1\/3 near pancreas body and splenic vessels.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1405\" height=\"929\" src=\"https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/adrenal-vascular-supply-and-AVS.jpg\" alt=\"\" class=\"wp-image-4417743\" srcset=\"https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/adrenal-vascular-supply-and-AVS.jpg 1405w, https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/adrenal-vascular-supply-and-AVS-300x198.jpg 300w, https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/adrenal-vascular-supply-and-AVS-768x508.jpg 768w\" sizes=\"auto, (max-width: 1405px) 100vw, 1405px\" \/><figcaption class=\"wp-element-caption\">Anatomy of the Adrenal Gland<\/figcaption><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">Blood Supply<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Arterial Supply<\/strong>: Extremely rich and variable, with 12 or more small arterial branches.\n<ul class=\"wp-block-list\">\n<li><strong>Superior Adrenal Artery<\/strong> (from <strong>inferior phrenic<\/strong>),<\/li>\n\n\n\n<li><strong>Middle Adrenal Artery<\/strong> (from <strong>aorta<\/strong>),<\/li>\n\n\n\n<li><strong>Inferior Adrenal Artery<\/strong> (from <strong>renal artery<\/strong>).<\/li>\n\n\n\n<li>Arteries encircle the gland, forming a network to supply cortex and medulla.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Venous Drainage<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Right <a href=\"https:\/\/myendoconsult.com\/learn\/localization-of-source-of-hyperaldosteronism-adrenal-vein-sampling\/\" data-wpil-monitor-id=\"147\">Adrenal Vein<\/a><\/strong> \u2192 directly into <strong>IVC<\/strong>; ~4\u20135 mm long.<\/li>\n\n\n\n<li><strong>Left <a href=\"https:\/\/myendoconsult.com\/learn\/adrenal-vein-sampling-interpretation\/\" data-wpil-monitor-id=\"148\">Adrenal Vein<\/a><\/strong> \u2192 <strong>left renal vein<\/strong> (often joined by left inferior phrenic vein).<\/li>\n\n\n\n<li>Both adrenals have a single large central vein that collects blood from cortex &amp; medulla.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\">Adrenal Vasculature Integration<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Cortical-&gt;Medullary Flow<\/strong>\n<ul class=\"wp-block-list\">\n<li>Cortisol-rich blood from cortical sinusoids flows into medullary sinusoids.<\/li>\n\n\n\n<li>Enhances phenylethanolamine-N-methyltransferase (PNMT) activity, converting norepinephrine to <strong>epinephrine<\/strong> in medulla.<\/li>\n\n\n\n<li>Extra-adrenal chromaffin sites lack this high cortisol \u2192 produce mostly norepinephrine.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Surgical Approaches to the Adrenal Glands<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Open Transabdominal<\/strong>\n<ul class=\"wp-block-list\">\n<li>Incision: Extended subcostal or midline (for bilateral disease).<\/li>\n\n\n\n<li>Left adrenal: via <strong>gastrocolic ligament<\/strong> into lesser sac \u2192 mobilize pancreas, open Gerota fascia, retract kidney.<\/li>\n\n\n\n<li>Right adrenal: mobilize hepatic flexure, retract right liver lobe upward.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Open Posterior<\/strong>\n<ul class=\"wp-block-list\">\n<li>Patient prone; less postoperative pain, reduced ileus.<\/li>\n\n\n\n<li>Curvilinear incision (10th rib to iliac crest) or resection of 12th rib. Access behind kidney.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Laparoscopic Transabdominal<\/strong>\n<ul class=\"wp-block-list\">\n<li>Standard approach for unilateral masses &lt;8 cm with no suspicion of invasive malignancy.<\/li>\n\n\n\n<li>Patient lateral decubitus; typically 4 trocars below costal margin.<\/li>\n\n\n\n<li>Right side: Retract liver; left side: mobilize colonic flexure.<\/li>\n\n\n\n<li>Lower morbidity, faster recovery.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Posterior Retroperitoneoscopic<\/strong>\n<ul class=\"wp-block-list\">\n<li>Patient prone, 3 trocars in flank.<\/li>\n\n\n\n<li>Insufflation of retroperitoneal space (20\u201325 mm Hg).<\/li>\n\n\n\n<li>Good for patients with prior abdominal surgeries (no adhesions).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Keys to Success<\/strong>\n<ul class=\"wp-block-list\">\n<li>Careful patient selection, knowledge of anatomy, gentle tissue handling, meticulous hemostasis, awareness of vascular anomalies.<\/li>\n\n\n\n<li>Adrenal parenchyma is fragile.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">INNERVATION OF THE ADRENAL GLANDS<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Sympathetic Innervation<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Preganglionic Fibers<\/strong>\n<ul class=\"wp-block-list\">\n<li>Arise from T11\u2013L2 spinal cord segments (lateral horns).<\/li>\n\n\n\n<li>Travel via <strong>white rami<\/strong> \u2192 <strong>splanchnic nerves<\/strong> (greater, lesser, least) \u2192 celiac, aorticorenal, renal ganglia.<\/li>\n\n\n\n<li>Many fibers <strong>pass through<\/strong> these ganglia without synapsing \u2192 form <strong>adrenal plexus<\/strong> on the gland\u2019s medial border.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Medullary Innervation<\/strong>\n<ul class=\"wp-block-list\">\n<li>Preganglionic fibers terminate directly on <strong>chromaffin cells<\/strong> (equivalent to postganglionic sympathetic neurons).<\/li>\n\n\n\n<li>Some small ganglia exist within medulla or near vessels.<\/li>\n\n\n\n<li>Parasympathetic supply from the <strong>celiac branch of posterior vagal trunk<\/strong> may also reach the adrenal plexus.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\">Functional Significance<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Chromaffin Cells<\/strong> (in medulla) release <strong>epinephrine<\/strong>, <strong>norepinephrine<\/strong>, and dopamine.<\/li>\n\n\n\n<li><strong>Fight-or-Flight Response<\/strong> triggered by hypothalamus, pons, medulla \u2192 sympathetic outflow to T\/L spine \u2192 adrenal medulla.<\/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\">HISTOLOGY OF THE ADRENAL GLANDS<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Cortex and Medulla<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Cortex<\/strong> (~90% of adult adrenal)\n<ul class=\"wp-block-list\">\n<li>Embryological origin: <strong>Mesoderm<\/strong>.<\/li>\n\n\n\n<li>3 Zones: <strong><a href=\"https:\/\/myendoconsult.com\/learn\/the-zona-glomerulosa-of-the-adrenal-gland\/\" data-wpil-monitor-id=\"151\">Zona glomerulosa<\/a>, fasciculata, reticularis<\/strong>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Medulla<\/strong> (~10% of adult adrenal)\n<ul class=\"wp-block-list\">\n<li>Embryological origin: <strong>Neural crest<\/strong>.<\/li>\n\n\n\n<li>Contains <strong>chromaffin cells<\/strong> producing catecholamines (epinephrine &gt; norepinephrine).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Adrenal Cortex Details<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Zona Glomerulosa<\/strong>\n<ul class=\"wp-block-list\">\n<li>Outer thin layer: cells arranged in loops or \u201cglomeruli.\u201d<\/li>\n\n\n\n<li>Secretes <strong><a href=\"https:\/\/myendoconsult.com\/learn\/topics\/aldosteronism\/\"  data-wpil-monitor-id=\"339\">aldosterone<\/a><\/strong> (mineralocorticoid), regulates Na\u207a\/K\u207a balance.<\/li>\n\n\n\n<li>Largely independent of ACTH; controlled by <strong>renin\u2013angiotensin<\/strong> system.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong><a href=\"https:\/\/myendoconsult.com\/learn\/zona-fasciculata-of-the-adrenal-gland\/\" data-wpil-monitor-id=\"152\">Zona Fasciculata<\/a><\/strong>\n<ul class=\"wp-block-list\">\n<li>Middle broad layer: cells in long straight cords (\u201cfascicles\u201d), rich in lipid vacuoles.<\/li>\n\n\n\n<li>Produces <strong>cortisol<\/strong> (glucocorticoid).<\/li>\n\n\n\n<li>Dependent on pituitary ACTH.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Zona Reticularis<\/strong>\n<ul class=\"wp-block-list\">\n<li>Inner layer next to medulla, cords form reticular network.<\/li>\n\n\n\n<li><a href=\"https:\/\/myendoconsult.com\/learn\/bilateral-cortisol-secreting-tumors\/\" data-wpil-monitor-id=\"149\">Secretes cortisol<\/a> and some <strong>adrenal androgens<\/strong> (e.g., DHEA).<\/li>\n\n\n\n<li>Also dependent on ACTH.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Blood Supply<\/strong>\n<ul class=\"wp-block-list\">\n<li>30\u201350 small arteries \u2192 capsular plexus \u2192 radial capillaries in cortex \u2192 drains into medullary sinusoids \u2192 single central <a href=\"https:\/\/myendoconsult.com\/learn\/adrenal-vein-sampling-testing-procedure\/\"  data-wpil-monitor-id=\"340\">adrenal vein<\/a>.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\">Adrenal Medulla Details<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Columnar Chromaffin Cells<\/strong>\n<ul class=\"wp-block-list\">\n<li>Produce <strong>epinephrine<\/strong> (\u223c80%) and <strong>norepinephrine<\/strong> (\u223c20%), small amounts of dopamine.<\/li>\n\n\n\n<li>Stain brown with chromium salts (oxidation of catecholamines).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Direct Sympathetic Innervation<\/strong>\n<ul class=\"wp-block-list\">\n<li>Preganglionic fibers release ACh onto chromaffin cells \u2192 catecholamine secretion.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Vessels<\/strong>\n<ul class=\"wp-block-list\">\n<li>Arterial supply from short cortical arteries passing straight into medulla + venous outflow from cortical sinusoids.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>DEVELOPMENT OF THE ADRENAL GLANDS Historical Note Overview Cortical Development Medullary Development Accessory and Absent Glands ANATOMY AND BLOOD SUPPLY OF THE ADRENAL GLANDS&hellip;<\/p>\n","protected":false},"featured_media":0,"template":"","oen_topic_chapter":[684],"class_list":["post-4422379","oen_topic","type-oen_topic","status-publish","hentry","oen_topic_chapter-adrenal-gland"],"_links":{"self":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422379","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":5,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422379\/revisions"}],"predecessor-version":[{"id":4422828,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422379\/revisions\/4422828"}],"wp:attachment":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/media?parent=4422379"}],"wp:term":[{"taxonomy":"oen_topic_chapter","embeddable":true,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic_chapter?post=4422379"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}