Final answer:
The loop of Henle and the collecting ducts are located in the medulla of the kidney for a specific reason: to create an osmotic gradient and aid in the formation of concentrated urine. The loop of Henle creates a concentration gradient by changing the permeability of its membrane to water and solutes. The collecting ducts play a role in the reabsorption of water through the insertion of aquaporin channel proteins.
Step-by-step explanation:
The loop of Henle and the collecting ducts are located in the medulla of the kidney for a specific reason. The loop of Henle is responsible for creating an osmotic gradient in the medulla, which is necessary for the formation of concentrated urine. The descending limb of the loop of Henle is permeable to water, allowing water to be reabsorbed into the medulla, while the ascending limb is impermeable to water, allowing solutes to be reabsorbed. This creates a concentration gradient that helps concentrate the urine.
The collecting ducts, on the other hand, collect filtrate from several nephrons and play a role in the reabsorption of water. When stimulated by antidiuretic hormone (ADH), the cells in the collecting ducts insert aquaporin channel proteins into their membranes, allowing water to pass from the duct lumen into the interstitial spaces, where it can be recovered by the vasa recta. This process allows for the recovery of large amounts of water from the filtrate, helping to concentrate the urine.