Practice question

Gradients of progesterone secreted by cumulus cells surrounding ovulated oocyte attract capacitated sperm via chemotaxis. Cumulus-derived nanomolar to micromolar progesterone is detected by sperm membrane hydrolase ABHD2 that degrades 2-arachidonoylglycerol, relieving inhibition of CatSper calcium channel, producing chemotactic calcium transients steering flagellar bending toward source. Experimental microfluidic assays show accumulation of human sperm toward progesterone sources. This chemical attraction operates at short range close to oocyte, refining navigation after long-range thermotaxis and rheotaxis toward fertilization site, improving encounter rates for successful conception and zygote formation.