The union of a male and a female gamete produces a zygote - The duration of a contraction is timed from the moment that the uterine muscle begins to tense to the moment that it reaches full relaxation

- The duration of a contraction is timed from the moment that the uterine muscle begins to tense to the moment that it reaches full relaxation. It’s measured in seconds.

- The union of a male and a female gamete produces a zygote, which divides into the fertilized ovum.