100+ Free ABB Andrology Practice Questions

Explanation: The WHO 6th edition (2021) sets the 5th-percentile lower reference limit for sperm concentration at 16 million spermatozoa per mL, a slight increase from the 15 million/mL value of the 5th edition. Values below this limit may warrant further evaluation but are not strict diagnostic thresholds.

Explanation: The WHO 6th edition lists the 5th-percentile lower reference limit for total motility (progressive plus non-progressive) at 42%. Progressive motility alone has a separate lower limit of 30%.

Explanation: The WHO 6th edition sets the progressive motility lower reference limit at 30%. Progressive motility refers to spermatozoa moving actively, either linearly or in a large circle, regardless of speed.

Explanation: The WHO 6th edition retains a normal morphology lower reference limit of 4% using strict (Tygerberg/Kruger) criteria. A sample is considered to meet the reference limit if at least 4% of evaluated spermatozoa have normal forms.

Explanation: The WHO 6th edition sets the lower reference limit for semen volume at 1.4 mL. Low volume (hypospermia) may indicate retrograde ejaculation, ejaculatory duct obstruction, or incomplete collection.

Explanation: FSH acts on Sertoli cells, stimulating them to support and nourish developing germ cells and to produce androgen-binding protein and inhibin B. LH, by contrast, acts on Leydig cells to stimulate testosterone production.

Explanation: Leydig cells, located in the interstitial tissue between seminiferous tubules, produce testosterone in response to LH. Testosterone is essential for spermatogenesis and the development of male secondary sex characteristics.

Explanation: Human spermatogenesis takes approximately 64 to 74 days from spermatogonial division to release of spermatozoa, plus additional time for transit and maturation in the epididymis. This timeframe is clinically relevant when evaluating the effect of interventions on semen parameters.

Explanation: Spermatozoa leaving the testis are largely immotile and non-fertile. They acquire progressive motility and fertilizing potential as they mature during transit through the epididymis, particularly the corpus and cauda regions.

Explanation: The seminal vesicles contribute the largest fraction of ejaculate volume (roughly 60-70%) and supply fructose, which serves as the principal energy source for sperm motility. Low or absent fructose can indicate seminal vesicle dysfunction or ejaculatory duct obstruction.