CorpusHuman Anatomy
EndocrineGland

Adrenal (suprarenal) gland

Glandula suprarenalis

Also known as: suprarenal gland, adrenals

Paired retroperitoneal glands (≈4–5 g each) capping the upper poles of the kidneys, each made of an outer steroid-secreting cortex and an inner catecholamine-secreting medulla.

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Overview

Mass≈4–5 g each
Size≈5 × 3 × 1 cm
Cortex : medulla≈85 : 15

Each adrenal gland is really two glands with different origins and control. The cortex (≈80–90 %, mesodermal) synthesises steroid hormones from cholesterol in three concentric zones — glomerulosa (aldosterone), fasciculata (cortisol) and reticularis (adrenal androgens). The medulla (≈10–20 %, neural crest) is a modified sympathetic ganglion whose chromaffin cells secrete epinephrine and norepinephrine when stimulated by preganglionic sympathetic fibres.

The right gland is pyramidal, lies posterior to the inferior vena cava and the bare area of the liver and rests on the right crus of the diaphragm. The left gland is crescentic (semilunar), extends down the medial border of the left kidney towards the hilum and is related anteriorly to the stomach (across the omental bursa), pancreas and splenic vessels. Both lie within the renal (Gerota) fascia but in a separate compartment from the kidney, separated by perirenal fat, so they stay in place when a kidney is ectopic or removed.

Blood flows centripetally: arteries form a subcapsular plexus, sinusoids run between the cortical cords carrying steroids inward, and drain into medullary venules — so medullary chromaffin cells are bathed in high concentrations of cortisol, which induces PNMT for epinephrine synthesis.

Location

Retroperitoneum at about T11–T12, on the superomedial aspect of each kidney, enclosed in renal fascia.

Parts & subdivisions

  1. Cortex
    Outer steroid-producing layer — zona glomerulosa, fasciculata, reticularis.
  2. Medulla
    Inner neural-crest-derived catecholamine-producing core.
  3. Capsule
    Fibrous capsule with the subcapsular arterial plexus.
  4. Central (suprarenal) vein
    Single large vein leaving at the hilum.

Anatomy

Innervation

Rich sympathetic supply from the coeliac plexus and the thoracic splanchnic nerves (greater, lesser, least). Preganglionic sympathetic fibres pass through the coeliac plexus without synapsing and end directly on chromaffin cells (nicotinic receptors) — the medulla is the equivalent of a sympathetic ganglion.

Arterial supply

Three arteries per side: superior suprarenal (from the inferior phrenic artery), middle suprarenal (directly from the abdominal aorta) and inferior suprarenal (from the renal artery), which break into ≈50 small branches that pierce the capsule.

Venous drainage

One central vein each: right suprarenal vein → inferior vena cava (very short — a hazard at right adrenalectomy); left suprarenal vein → left renal vein (often joined by the left inferior phrenic vein).

Lymphatic drainage

Lumbar (para-aortic) lymph nodes.

Relations

Right: IVC (anteromedial), bare area of liver (anterolateral), right crus of diaphragm (posteromedial), upper pole of right kidney (inferior). Left: stomach and omental bursa, body of pancreas and splenic vessels (anterior), left crus of diaphragm (posterior), medial border of left kidney and renal vessels (inferior).

Development

Cortex from intermediate mesoderm (coelomic epithelium adjacent to the gonadal ridge — hence shared steroidogenic enzymes with gonads); the fetal adrenal is very large (fetal zone) and involutes in the first months after birth. Medulla from neural crest cells that invade the cortex.

Function

  • Cortex: mineralocorticoids (salt and water, potassium), glucocorticoids (metabolism, stress, immunity) and androgen precursors.
  • Medulla: epinephrine and norepinephrine for the fight-or-flight response.

Clinical significance

Adrenal incidentaloma

A mass found on imaging for another reason (≈3–7 % of abdominal CTs in adults, more with age). Assess for hormone excess (dexamethasone suppression, metanephrines, aldosterone:renin ratio if hypertensive) and malignancy risk (size >4 cm, high Hounsfield attenuation).

Waterhouse–Friderichsen syndrome

Bilateral adrenal haemorrhage in fulminant sepsis, classically meningococcal, causing acute adrenal insufficiency, shock and purpura.

Neuroblastoma

Childhood tumour of neural-crest cells, most often in the adrenal medulla: abdominal mass crossing the midline, raised urinary VMA/HVA, MYCN amplification in aggressive forms, opsoclonus–myoclonus.

Compiled from standard anatomy and physiology references — see the Endocrine System sources. For education only; not medical advice.