Final answer:
The nephron is the kidney's functional unit responsible for filtering blood and forming urine through processes like glomerular filtration, tubular reabsorption, and tubular secretion.
Step-by-step explanation:
The functional unit of the kidney is the nephron. Each kidney contains over one million nephrons. These nephrons perform essential functions such as glomerular filtration, tubular reabsorption, and tubular secretion, which are all crucial in the production of urine. The nephron itself consists of several parts: the renal corpuscle, the renal tubule, and an associated capillary network, which originates from the cortical radiate arteries. There are two main types of nephrons: cortical nephrons, which make up 85 percent and are located deep in the renal cortex, and juxtamedullary nephrons, which make up 15 percent and are located close to the renal medulla.