What is the term for the network of capillaries that performs the first step in filtering blood?

The glomerulus is a crucial part of the nephron, which is the functional unit of the kidney. It consists of a network of tiny blood vessels (capillaries) where the first step in the filtration of blood occurs. In this process, blood enters the glomerulus under pressure, and this pressure facilitates the movement of water, salts, glucose, and waste products from the bloodstream into the Bowman's capsule, a cup-shaped structure surrounding the glomerulus. This initial filtration is vital in the formation of urine and the regulation of fluid and electrolyte balance in the body.

The nephron itself is the broader structure that includes the glomerulus but also encompasses other sections where additional processing of the filtrate occurs. The liver and adrenal glands do play important roles in the body's overall physiology, such as metabolism and hormone production, respectively, but they are not directly involved in the initial filtration of blood that happens at the glomerulus.