What is the functional unit of the kidney called?

The functional unit of the kidney is known as the nephron. Each kidney contains approximately one million nephrons, which are responsible for various essential functions in the process of filtering blood and forming urine. The nephron consists of several parts, including the glomerulus, renal tubules, and collecting duct. The glomerulus acts as a filtration system, where blood is filtered to remove waste and excess substances, while the renal tubules reabsorb important nutrients and water back into the bloodstream. This intricate structure enables the kidneys to maintain homeostasis in the body by regulating water, electrolytes, and waste.

The other terms refer to related but different concepts; for instance, glomerulus describes a specific part of the nephron responsible for filtration. Nephritis is a medical condition involving inflammation of the nephron and does not represent a structural or functional unit. The renal pyramid refers to a component within the renal medulla that contains the collecting ducts and is involved in the concentrating of urine but does not function independently as a unit. Thus, the nephron is the correct answer, as it encapsulates the entire functional aspect of kidney filtration and urine production.