Adrenal Gland in Young Mice

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Adrenal glands are located near the anterior poles of the kidneys and consist of cortex and medulla surrounded by a fibrous connective tissue capsule. The medulla is composed of irregular groups of polyhedral cells separated by sinusoids. In humans and most mammals three zones can be distinguished in the cortex, but the cortex of the mouse adrenal gland has only two zones: zona glomerulosa and zona fasciculata. The zona glomerulosa is narrow and consists of small cells. The zona fasciculata is wide and contains cells whose cytoplasm appears foamy due to the presence of lipid droplets. In young mice, the cortex exhibits a unique zone, the X-zone, which is formed by basophilic cells that surround the medulla. The X-zone appears at approximately 10 days of age and disappears at sexual maturity in male mice or first pregnancy in female mice. Adrenal glands are larger in female mice than in male mice. Ectopic adrenal glands are common in mice.

The 4X micrograph is a cross section of an adrenal gland of a young mouse, showing the capsule, the cortex, the X-zone, and the medulla. The 10X, 20X, and 40X micrographs display, in increasing detail, the cortex, the X-zone, and the medulla. In the 20X micrograph both zones of the cortex are visible. The 40X micrograph depicts the zona fasciculata and the basophilic cells of the X-zone.