The nephron is considered the "functional unit" of the kidney. Each nephron consists of renal capillaries and a fluid-collecting duct that filters plasma received from the renal artery.
From the afferent arterioles, blood is delivered to the glomerulus within the nephron, a series of capillary loops enclosed by a sac-like structure called the Bowman's capsule. At the glomerulus, blood passes through a specialized cellular ultrastructure that filters the plasma. Water is freely filtered, while other components are more selectively filtered based on size and charge, with larger and/or more negatively charged components filtered less easily.
The filtrate passes into the Bowman's capsule, then flows through additional sections of the nephron, beginning with the proximal tubule, moving through the loop of Henle, and finally, the distal tubule. Throughout this process, various components of the filtrate are reabsorbed, including water and electrolytes. The remainder of the filtrate is delivered to larger collecting tubules and ducts, which are ultimately passed out of the kidney via the ureter.
