Anatomy and Physiology II Practice Test

Which two parts of the renal tubules extend into the renal medulla?

1. Proximal tubule and distal tubule

2. Loop of Henle and collecting duct

3. Renal corpuscle and medullary rays

4. Renal tubule and nephron loop

The correct answer is: Loop of Henle and collecting duct

The two parts of the renal tubules that extend into the renal medulla are the Loop of Henle and the collecting duct. The Loop of Henle plays a critical role in concentrating urine and maintaining the body’s water balance. It has a descending limb that is permeable to water and an ascending limb that is impermeable to water but allows for ion transport. This creates a concentration gradient in the medulla that is essential for the kidney's ability to concentrate urine. The collecting duct is also essential as it receives urine from multiple nephrons and facilitates the final stages of water reabsorption and the regulation of electrolyte balance. As the collecting duct travels through the medulla, it becomes permeable to water, allowing for further concentration of urine depending on the body's hydration status and the action of hormones like antidiuretic hormone (ADH). The other options do not describe parts of the renal tubules that extend into the medulla. The proximal tubule and distal tubule are located in the renal cortex, while the renal corpuscle is the initial filtration component of the nephron and does not extend into the medulla. Medullary rays refer to structures within the renal cortex, not the tubules that penetrate the medulla.