Essential anatomy of the kidney

Abstract

A knowledge of the structure of the kidney is essential to the understanding of its function. In general, structure and function are dealt with together in this book and this chapter therefore consists of only a brief outline of those structural features which are of particular importance, or which are not dealt with in detail elsewhere. 2.2 General morphology and cellular organization The kidneys are situated behind the peritoneum on each side of the vertebral column. In man, the top (upper pole) of each kidney is at the level of the twelfth thoracic vertebra and the bottom (lower pole) is at the level of the third lumbar vertebra. Each kidney is about 12 cm long and weighs about 150 g. On the medial surface of each kidney (the concave surface) is a slit, the hilus, through which pass the renal artery and vein, the lymphatics, the renal nerve and the renal pelvis, which is the funnel-shaped upper end of the ureter. The blood supply to each kidney is usually a single renal artery arising from the abdominal aorta. However, there may sometimes be additional small vessels from superior mesenteric, adrenal, spermatic or ovarian arteries. If a kidney is bisected from top to bottom (Figure 2.1), the cut surface shows two distinct regions, a dark outer region, the cortex, and a paler inner region, the medulla, which is further divided into a number of conical areas, the renal pyramids. The apex of each pyramid extends towards the renal pelvis, forming a papilla. Some animal species have only one pyramid (and papilla) in each kidney. Striations can be seen on the renal pyramids. These are medullary rays, which are attributed to the straight tubular elements (collecting ducts and loops of Henle) and blood vessels (vasa recta) in this region. 20 C. Lote, Principles of Renal Physiology