Topography and appearance
Both adrenal glands are securely embedded in adipose tissue and enclosed within the common renal fascia. Despite being paired, these organs differ in shape and exact location:
- The right adrenal gland is located slightly higher than its counterpart and has a triangular shape.
- The left adrenal gland has a characteristic semilunar ( crescent ) shape. Its lower part partially abuts the medial margin of the upper pole of the left kidney.
Surfaces and margins
In anatomy, each adrenal gland traditionally features three main surfaces:
- Anterior surface (facies anterior).
- Posterior surface (facies posterior).
- Renal surface (facies renalis), which faces directly toward the kidney.
In addition, two margins are described: the superior margin (margo superior) and the medial margin (margo medialis). Special attention should be paid to the anteromedial surface — this is where the adrenal hilum (hilum) is located. A large blood vessel, the central adrenal vein (v. suprarenalis), exits the organ through this structure.
Internal structure: capsule and parenchyma
Externally, the organ is covered by a thin fibrous capsule containing smooth muscle fibers. Connective tissue septa extend from this capsule into the gland, forming a framework.
The gland parenchyma itself is visually and functionally divided into two contrasting layers:
1. Adrenal cortex (cortex) It constitutes the bulk of the organ, has a yellowish-brown hue, and consists of three consecutive zones:
- Zona glomerulosa (zona glomerulosa): responsible for the production of mineralocorticoids (primarily aldosterone).
- Zona fasciculata (zona fasciculata): synthesizes glucocorticoids (e.g., hydrocortisone).
- Zona reticularis (zona reticularis): is the site of sex hormone (androgen) production.
2. Adrenal medulla (medulla) Located in the very center, it has a rich brownish-red color. It consists of specialized chromaffin cells of epithelial origin. These cells secrete vital stress hormones — adrenaline and noradrenaline. Their release leads to increased excitation and contraction force of the myocardium, heightened tone of the sympathetic nervous system, and, consequently, elevated blood pressure.
Briefly: answers to topical questions
Which arteries supply blood to the adrenal glands?
Blood supply to the adrenal glands comes from three main arterial sources.
- Superior suprarenal artery (a. suprarenalis superior) — branches off the inferior phrenic artery and heads toward the adrenal cortex.
- Middle suprarenal artery (a. suprarenalis media) — is a paired visceral branch of the abdominal aorta.
- Inferior suprarenal artery (a. suprarenalis inferior) — branches off the renal artery.
These arteries form a triple blood supply and anastomose with one another within the gland.
Where does the central vein of the right and left adrenal glands drain?
The central adrenal vein (v. suprarenalis) exits through the hilum of the gland and has different drainage pathways on the right and left sides.
- Right suprarenal vein (v. suprarenalis dextra) — drains directly into the inferior vena cava (v. cava inferior).
- Left suprarenal vein (v. suprarenalis sinistra) — most commonly drains into the left renal vein (v. renalis sinistra).
Which nerve plexuses and fibers provide innervation to the adrenal glands?
Innervation of the adrenal glands is provided via the suprarenal plexus (plexus suprarenalis), which accompanies the adrenal blood vessels. The celiac plexus (plexus celiacus) is located near the adrenal glands; secondary plexuses branch off from it, accompanying the blood vessels and innervating the organs.
Which organs are in contact with the anterior surface of the right adrenal gland?
The anterior surface of the right adrenal gland is in contact with the liver.
- Liver (hepar) — its extraperitoneal surface adjoins the anterior surface of the right adrenal gland.
It is also worth noting that medially, the right adrenal gland contacts the inferior vena cava (v. cava inferior), which runs along its medial margin.
The zones of the cortex are easily remembered from the capsule inward using the mnemonic: Zona glomerulosa, Zona fasciculata, Zona reticularis.
Class and exam questions
What is the anatomical difference between the right and left adrenal glands?
The right adrenal gland has a triangular shape and is located higher, whereas the left is semilunar and partially adjacent to the medial margin of the superior pole of the kidney.
Where is the adrenal hilum located and what passes through it?
The hilum (hilum) is located on the anteromedial surface of the organ. The central adrenal vein (v. suprarenalis) emerges from it.
Which hormones are produced by the different cortical zones?
The zona glomerulosa synthesizes aldosterone (mineralocorticoids), the zona fasciculata synthesizes hydrocortisone (glucocorticoids), and the zona reticularis synthesizes androgens (sex hormones).
What else to study on this topic
- Structural features of the fibrous capsule and the role of smooth muscle fibers
- Histological characteristics of medullary chromaffin cells
- The relationship between medullary hormones and the sympathetic nervous system
- Mechanisms of adrenaline's effects on blood pressure and the heart
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