What comprises the nephron in the human body?

The nephron is the fundamental structural and functional unit of the kidney, responsible for filtering blood and forming urine. It comprises two main components: the glomerulus and a tubule. The glomerulus is a network of capillaries that performs the initial filtration of blood, allowing water, ions, and small molecules to pass while retaining larger molecules and blood cells. Following this, the tubular system, which includes segments like the proximal convoluted tubule, loop of Henle, and distal convoluted tubule, processes the filtrate through reabsorption and secretion to form urine.

While the other choices mention components related to kidney function, they do not accurately represent the basic structural unit—the nephron. For instance, the renal pelvis is an area that collects urine but is not part of a nephron. Similarly, the cortex and medulla refer to the kidney's outer and inner regions, respectively, not the nephron itself. Lastly, the proximal and distal convoluted tubules are parts of the nephron but do not encompass the full structure, which also includes the glomerulus. Thus, the complete understanding of the nephron's components is captured accurately in the first choice.