AP BIOLOGY

Detailed explanation-1: -The correct answer is option (c) juxtamedullary nephron. The juxtamedullary nephrons play an important role in producing concentrated urine.

Detailed explanation-2: -The nephron loop of juxtamedullary nephrons is the apparatus that allows the nephron to concentrate urine. The loop is a countercurrent multiplier system in which fluids move in opposite directions through side‐by‐side, semi‐permeable tubes.

Detailed explanation-3: -Although both cortical and juxtamedullary nephrons regulate the concentrations of solutes and water in the blood, countercurrent multiplication in the loops of Henle of juxtamedullary nephrons is largely responsible for developing the osmotic gradients that are needed to concentrate urine.

Detailed explanation-4: -Each nephron consists of a ball formed of small blood capillaries, called a glomerulus, and a small tube called a renal tubule. Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney. Two ureters.

Detailed explanation-5: -Cortical nephrons have a glomerulus located nearer to the outer parts of the cortex and their loops of Henle are short. Juxtamedullary nephrons have a glomerulus near the junction of the cortex and medulla and their loops of Henle penetrate deep into the medulla.