The official term for these glands is 'suprarenal', but everyone I know refers to them as the adrenals.
Structure
The paired adrenal glands are quite different in their shape. Each contains an external cortex (under pituitary / endocrine control) and a central medulla (sympathetic nervous tissue).
The right adrenal gland is pyramidal in shape, and lies on the apex of the right kidney. The left adrenal gland has a crescent shape, and lies on the supero-medial aspect of the left kidney. Each gland has a hilum from which lymphatics and veins leave; arterial supply and innervation is variable.
Macroscopic Appearance
The adrenals are yellow in a living person.
Microscopic Appearance
The cortex is arranged in three distinct layers with an outer capsule. The thin, outer zona glomerulosa contains dense, darkly staining cells and produces aldosterone. The large fascicular zone contains cells arranged in cords, and produces cortisol. The inner reticular zone has irregular cords with intervening spaces, and produces sex hormones (oestrogen/progesterone/androgens).
The medulla contains an irregular arrangement of chromaffin cells.
Location
The right adrenal gland lies on the top of the right kidney, whereas the left adrenal is slightly medial (although still on the superior pole of the kidney).
Relations
Right adrenal
The gland is superior to the right kidney and posterior to the inferior vena cava, both of which are closely related. It is also posterior to the right lobe of the liver. The gland is anterior of the right crus of the diaphragm.
Left adrenal
The left adrenal lies just anterior to the left crus of diaphragm. The left kidney lies lateral and inferiorly. The stomach lies superiorly, separated by peritoneum which coats the gland and the stomach.
