Anatomy and Position of the Kidney in the body

The kidney is a fascinating and under-appreciated organ. Even its name is interesting: while the Greek nephros and the Latin renes are both used as medical terms for the kidney and its anatomy, the origin of the common name in English - “kidney” - is actually unknown. It may be from the Old English terms cwið (womb) + ey (egg), from its shape, but there is no clear consensus on its origins.

The kidney serves many functions, but its most obvious is creating urine. The process of doing that is surprisingly complex, and involves regulation of blood pressure, re-absorbing vital nutrients, excreting urea from protein catabolism, and secreting hormones such as erythropoietin (which stimulates red blood cell creation).

These are four major sections of the kidney:

  • Capsule - A tough, fibrous layer of tissue, surrounded by a thick layer of fat, which protects the kidney.
  • Cortex - Just inside the capsule, the outermost layer of the kidney itself, which contains renal corpuscules and tubules. Ultrafiltration and erythropoietin production happens here.
  • Medulla -  The inner tissue of the kidney, split up into renal pyramids. This is where the arteries split up, serum comes out of the blood, and ions and glucose are processed.
  • Renal Pelvis - This is the convergence point of the major calcyes, and funnels urine into the ureter, which goes to the bladder. The transitional epithelium in this section of the kidney is the cause of many types of kidney cancers.

Anatomy: Descriptive and Applied. Henry Gray, 1918.