What Happens to Sperm After Ejaculation

In numbers

• MeasuredA sperm cell is about 55 µm long; its head is about 4 µm
• MeasuredVaginal pH: about 3.8–4.5
• EstimateSperm arriving: typically 40–300 million

Every number is labelled measured, an estimate or drawn: how we know.

The science

A typical ejaculate is 1.5–5 mL. The WHO lower reference limits are 1.4 mL and 16 million sperm per mL, 39 million in total, and many men have far more. Vaginal pH is about 3.8–4.5, kept low by lactobacilli: the small rods drifting here. Semen is alkaline (pH 7.2–8): within seconds it lifts the vagina's pH to about 7, and the effect lasts up to about two hours. Within a minute it gels into a coagulum, which liquefies again over about 5–30 minutes. Sperm left behind in the vagina die within hours.

In Endo-View

This is chapter 1 of the journey to life, an interactive 3D simulation at true scale: watch it, slow it down or run it at real speed, and read every number with its label.

Watch it in 3D