Medulla - Overview

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The mouse kidney is covered by a thin connective tissue capsule and consists of, from its convex border to its concave border, a cortex, a medulla, and a single papilla that can be very long. The papilla drains into the renal pelvis, the anterior end of the ureter, which joins the kidney on its concave border at the hilus. The functional unit of the kidney is the nephron, which comprises a glomerulus (a capillary bed that is particularly small in the mouse) surrounded by the Bowman’s capsule, a proximal convoluted tubule, descending and ascending portions of the straight loop of Henle, and a distal convoluted tubule. In between the nephrons is delicate, richly vascular connective tissue. Nephrons drain into collecting tubules, which join to form larger collecting ducts (Bellini ducts) that open into the renal pelvis. In mice, particularly adult males, proteinuria is normal.

The medulla of the mouse kidney contains the ascending and descending portions of the loop of Henle, collecting tubules, and blood vessels (vasa recta). The loop of Henle has a thin wall lined by flattened epithelium, while the collecting tubules are lined by cuboidal epithelial cells whose nuclei bulge into the lumen.

The 4X micrograph provides an overview of the cortex, medulla and papilla of the mouse kidney. The 10X, 20X, and 40X micrographs show in increasing detail the loops of Henle, the collecting tubules, and the blood vessels. The flattened epithelial lining of the loops of Henle is visible in the 10X and 20X micrographs. The 10X, 20X, and 40X micrographs depict the collecting tubules’ cuboidal epithelium with nuclei that bulge into the lumen.