At what stage does a developing sperm cell begin to grow a tail?

A. collecting duct: While the collecting duct plays a critical role in final water reabsorption and urine concentration, it receives drainage from multiple nephrons. It is not considered the basic unit because it is shared among many functional units. Its activity is primarily regulated by antidiuretic hormone.

B. nephron: This is the microscopic structural and functional unit responsible for filtering blood and forming urine. Each kidney contains approximately 1 million nephrons, each consisting of a renal corpuscle and a renal tubule. It performs all primary renal functions including filtration, reabsorption, and secretion.

C. capsular space: This is the physical gap between the visceral and parietal layers of the glomerular capsule. It serves as the initial reservoir for glomerular filtrate before it enters the proximal tubule. It is merely a compartment within a larger structure rather than a complete functional unit.

D. nephron loop: Also known as the loop of Henle, this is a specific U-shaped segment of the renal tubule. It is essential for establishing the medullary osmotic gradient via the countercurrent multiplier system. It represents only one part of the entire nephron's complex tubular system.

E. glomerular capsule: This epithelial structure captures the fluid filtered from the glomerular capillaries. While it is a vital part of the renal corpuscle, it cannot function independently to produce urine without the associated glomerulus and tubules. It is a sub-component of the nephron unit.

A. not develop secondary sex characteristics: Secondary sex characteristics, such as muscle growth and hair distribution, are driven by testosterone produced by interstitial cells. Since LH levels are normal, these cells will still be stimulated to produce adequate testosterone. The boy would likely appear physically mature in terms of external male characteristics.

B. have impaired function of interstitial cells: Interstitial endocrine cells are specifically regulated by luteinizing hormone, which the question states is functioning normally. These cells will continue to synthesize testosterone regardless of the FSH deficiency. Their endocrine function remains intact because their primary tropic hormone is still present in the circulation.

C. be impotent (unable to have an erection): Erection is a neurovascular reflex mediated by the parasympathetic nervous system and is not directly dependent on FSH. While low testosterone can decrease libido, LH is present to maintain testosterone levels. Therefore, the physiological mechanism for erection should remain functional in this mature male.

D. be unable to produce viable sperm: Follicle-stimulating hormone is strictly required to stimulate the sustentacular cells to facilitate the final stages of sperm maturation. Without FSH, the process of spermatogenesis cannot be completed effectively, leading to infertility. The individual would produce few or no functional spermatozoa despite normal hormonal levels.