Final answer:
Filtration is the first step in urine formation, occurring in the glomerulus. Reabsorption mainly happens in the proximal convoluted tubule, whereas secretion of additional wastes and maintenance of homeostasis take place in other parts of the renal tubules.
Step-by-step explanation:
Filtration is the first step in urine formation, and it takes place in the glomerulus of the nephron, not in the proximal convoluted tubule, distal convoluted tubule, or collecting duct. During glomerular filtration, water and solutes are filtered out of the blood due to the pressure within the glomerular capillaries. This process results in a filtrate, which includes water, salts, organic solids such as nutrients, and waste products of metabolism like urea. The filtrate is then passed into Bowman's capsule and moves toward the proximal convoluted tubule.
After filtration, in the proximal convoluted tubule, reabsorption occurs. This step involves the movement of substances from the tubule back into the blood in the peritubular capillaries. Most of the solutes, along with water and organic solutes (mainly glucose and amino acids), are reabsorbed here.
Tubular reabsorption and tubular secretion occur in the renal tubules following filtration. Tubular secretion involves the transfer of additional solutes and wastes into the tubules, which is an essential step in adjusting the composition of the blood and urine.