Definition - What does Motile Sperm mean?
Motile sperm are sperm cells that are both structurally and functional healthy enough to be able to rhythmically swing their tail and move constantly in a forward direction. Once deposited in the vagina, sperm need to actively move through the vagina and uterus to the fallopian tubes to meet with an egg for fertilization to take place.
For successful conception, the percentage of motile sperm in semen typically needs to be more than 50%. Sperm motility is an important feature that is looked for during a sperm analysis when a man is being investigated to find the underlying cause of infertility.
FertilitySmarts explains Motile Sperm
Sperm need to travel a long distance from the vagina to the fallopian tubes to fertilize an egg, and out of the millions of sperm that are released into the vagina, only a few are able to survive this journey. The ability to maintain a progressive forward movement through the reproductive tract is key to a successful fertilization.
Even after a sperm has reached the egg, the sperm cell has to pass through the cells that line the egg as well as the outer wall of the egg and only the sperm that maintains constant motility is able to penetrate these barriers and fertilize the egg.
Sperm motility is important not only for normal conception but also for some assisted reproductive technologies (ART) such in vitro fertilization (IVF), as the sperm needs to progress towards the egg through the culture medium in a Petri dish (when intracytoplasmic sperm injection isn't used).
The tail of the sperm is the most important structure that determines the ability of sperm to be motile. Tail movements require a lot of energy that is supplied by mitochondria in the sperm cell in the form of ATP. Any structural abnormalities of the sperm or an abnormality in sperm function or metabolism can impair sperm mobility.