Sperm are microscopic, tadpole-shaped male reproductive cells. Each sperm cell has a head containing genetic material, a midpiece providing energy, and a tail that propels it forward. The primary function of sperm is to fertilize a female egg cell. Millions of these cells are released during ejaculation, though only one is needed for conception.
Sperm Survival Outside the Body
Sperm require specific conditions to remain viable. Once ejaculated and exposed to external environments, their lifespan dramatically shortens. They rapidly lose motility and die within minutes to seconds on dry surfaces due to dehydration, which compromises their structure and function.
When sperm come into contact with water, such as in a bath or hot tub, their survival is limited. Fresh water can cause sperm cells to burst due to osmotic pressure, and chemicals like chlorine quickly damage the cell membrane. Even at body temperature, dispersal from seminal fluid and chemical presence reduce viability to minutes. On surfaces like clothing or bedding, sperm viability is similarly short, lasting only a few minutes. The semen quickly dries, creating an unsuitable environment that leads to rapid loss of motility and cell death.
Sperm Survival Inside the Female Body
The female reproductive tract offers a more hospitable environment for sperm, extending their lifespan compared to external conditions. Upon entering the vagina, sperm encounter an acidic environment with a pH ranging from 3.8 to 4.5. This acidity is hostile to sperm, causing many to die within minutes to a few hours.
Surviving sperm continue their journey to the cervix. During ovulation, hormonal changes cause the cervical mucus to become thinner, more alkaline, and stretchy, resembling egg whites. This fertile cervical mucus provides a protective and nourishing medium, shielding sperm from vaginal acidity and facilitating movement. The cervical crypts, tiny channels within the cervix, can also act as temporary reservoirs, storing sperm and gradually releasing them over time.
Once sperm navigate the cervix and enter the uterus and fallopian tubes, their survival time increases. Muscular contractions within the uterus help propel sperm towards the fallopian tubes, where fertilization occurs. Under these optimal conditions, particularly when fertile cervical mucus is present and ovulation is near, sperm can survive for several days. The average survival time is 3 to 5 days, though some sperm may remain viable for up to 7 days, waiting for an egg to be released.