The male gamete in mammals is the sperm cell (spermatozoon). It is highly specialised to reach and fertilise the egg, and has three main regions.
• A haploid nucleus containing tightly packed DNA (23 chromosomes in humans), which will combine with the egg nucleus at fertilisation.
• An acrosome, a specialised lysosome made by the Golgi apparatus, covering the front of the head. It contains digestive (hydrolytic) enzymes that are released in the acrosome reaction to digest a path through the zona pellucida around the egg.Midpiece
• Packed with spirally arranged mitochondria, which carry out aerobic respiration to produce the ATP needed to power the tail.
• Contains a centriole at the base of the tail, from which the tail's microtubules grow.Tail (flagellum)
• Made of microtubules in a 9 + 2 arrangement, which slide past each other using ATP, so the tail beats and the sperm swims.Other adaptations: the sperm has very little cytoplasm, making it small and streamlined for swimming, and it is produced in enormous numbers (around 200 to 300 million per ejaculation in humans), increasing the chance that one reaches the egg.A human sperm is only about 50 to 60 µm long, most of which is the tail; the head is about 5 µm long.Worked example: a sperm swims at about 3 mm per minute. To travel 150 mm to the oviduct would take about 150 ÷ 3 = 50 minutes of swimming.
• A haploid nucleus containing tightly packed DNA (23 chromosomes in humans), which will combine with the egg nucleus at fertilisation.
• An acrosome, a specialised lysosome made by the Golgi apparatus, covering the front of the head. It contains digestive (hydrolytic) enzymes that are released in the acrosome reaction to digest a path through the zona pellucida around the egg.Midpiece
• Packed with spirally arranged mitochondria, which carry out aerobic respiration to produce the ATP needed to power the tail.
• Contains a centriole at the base of the tail, from which the tail's microtubules grow.Tail (flagellum)
• Made of microtubules in a 9 + 2 arrangement, which slide past each other using ATP, so the tail beats and the sperm swims.Other adaptations: the sperm has very little cytoplasm, making it small and streamlined for swimming, and it is produced in enormous numbers (around 200 to 300 million per ejaculation in humans), increasing the chance that one reaches the egg.A human sperm is only about 50 to 60 µm long, most of which is the tail; the head is about 5 µm long.Worked example: a sperm swims at about 3 mm per minute. To travel 150 mm to the oviduct would take about 150 ÷ 3 = 50 minutes of swimming.