What is the glomerulus primarily made up of?

The glomerulus is primarily made up of a tangled body of capillaries, known as glomerular capillaries, which are specialized for filtration. This network of capillaries is crucial in the kidney's function to filter blood and form urine. The structure allows for a large surface area that facilitates the filtration of water, ions, and small molecules from the blood into the Bowman’s capsule, initiating the process of urine formation.

This capillary structure is lined with specialized endothelial cells that possess fenestrations, enabling them to be selectively permeable. The arrangement and composition of the glomerulus are essential for maintaining proper kidney function and regulating blood composition. Glomerular filtration is a key first step in nephron function, and any disruption to this structure can lead to significant renal impairment.