What is the function of tail of human sperm?

The tail, or flagellum, of a human sperm cell helps it swim forward through female reproductive fluids to reach and fertilize the egg.

Structure of the sperm tail

The tail forms about 90 % of the sperm's total length. It is divided into:

• Midpiece: packed with mitochondria that make ATP energy
• Principal piece: long segment with axial microtubules
• End piece: tapering tip assisting fine steering

Movement mechanism

Inside the tail is an axoneme, a 9+2 microtubule arrangement. Dynein motor proteins make adjacent microtubules slide, bending the tail in a whip-like beat. Cyclic bends push against fluid, creating forward thrust.

Energy supply

Mitochondria in the midpiece burn fructose from seminal plasma, releasing ATP. This fuels dynein motors. Without enough ATP, the sperm tail cannot beat strongly, reducing fertility.

Role in fertilization

The sperm must travel about 15 cm in the female tract, many times its body length. The tail's rhythmic beating lets it navigate cervical mucus, uterine fluid, and the narrow oviduct. Some sperm tails also respond to chemical cues, guiding them toward the egg (chemotaxis).

Medical relevance

Conditions like asthenozoospermia (low motility) arise when tail structure or mitochondria are defective. Assisted reproductive technologies evaluate motility as a key parameter. Healthy tail activity increases the chance of natural conception.