Suprarenal Glands

Introduction

Overview of the Suprarenal Glands

The suprarenal (adrenal) glands are paired endocrine organs situated atop each kidney. They are part of the posterior abdominal wall and consist of an outer cortex and inner medulla, each producing distinct hormones. Their position in the retroperitoneal space makes them readily visible in gross dissection of the posterior abdomen.

Anatomical Position in the Posterior Abdominal Wall

Each gland lies in the subphrenic space, posterior to the diaphragm and anterior to the crus of the diaphragm, resting on the superior pole of the kidney. They are covered by a fibrous capsule and lie deep to the perirenal fat, separated from the posterior abdominal wall by the quadratus lumborum and psoas major muscles.

Study

Capsule and Cortex

The adrenal capsule is a thin, fibroelastic layer that encloses the gland. Beneath it, the cortex is organized into three concentric zones—zona glomerulosa, zona fasciculata, and zona reticularis—each synthesizing mineralocorticoids, glucocorticoids, and androgens respectively.

Medulla

The medulla occupies the central core of the gland and consists of chromaffin cells derived from neural crest. These cells secrete catecholamines (epinephrine and norepinephrine) directly into the bloodstream in response to sympathetic stimulation.

Vascular Supply

Arterial blood reaches the adrenal glands via three main sources: the superior suprarenal arteries (branches of the inferior phrenic artery), the middle suprarenal arteries (direct branches of the abdominal aorta), and the inferior suprarenal arteries (branches of the renal artery). Venous drainage occurs through the suprarenal veins into the inferior vena cava on the right and the renal vein on the left.

Innervation

Sympathetic innervation arises from the thoracic splanchnic nerves, which synapse in the pre‑ganglionic fibers that directly stimulate chromaffin cells. Parasympathetic input is minimal, reflecting the gland's primary role in rapid stress responses.

Relations to Adjacent Structures

Posteriorly, the gland is bounded by the diaphragm and the crus of the diaphragm; laterally, it contacts the 12th rib and the quadratus lumborum muscle. Anteriorly, it is separated from the stomach and pancreas by the peritoneum and the lesser sac, making it a key landmark in posterior abdominal wall dissections.

Summary

Key Takeaways

The suprarenal glands sit atop the kidneys within the posterior abdominal wall, encapsulated by a fibroelastic capsule and composed of a three‑zone cortex and a central medulla. Their rich arterial network derives from three distinct sources, and venous outflow differs between the right and left glands. Understanding their relationships to the diaphragm, renal vessels, and surrounding musculature is essential for accurate gross anatomical identification.

Clinical Correlate

Adrenal masses such as adenomas, pheochromocytomas, or metastatic lesions can alter the gland's size and vascular pattern, influencing surgical approaches to the posterior abdomen. Hemorrhage from the suprarenal veins may present as retroperitoneal bleeding, underscoring the importance of recognizing these structures during trauma assessment.