Sperm .January 13, 2021
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, “female” reproductive cell and a smaller, “male” one). Animals produce motile sperm with a tail known as a flagellum, which are known as spermatozoa, while some red algae and fungi produce non-motile sperm cells, known as spermatia. Flowering plants contain non-motile sperm inside pollen, while some more basal plants like ferns and some gymnosperms have motile sperm.
The mammalian sperm cell can be divided in 2 parts:
- Head: contains the nucleus with densely coiled chromatin fibers, surrounded anteriorly by a thin, flattened sac called the acrosome, which contains enzymes used for penetrating the female egg. It also contains vacuoles.
- Tail: also called the flagellum, is the longest part and capable of wave-like motion that propels sperm for swimming and aids in the penetration of the egg.
- The tail was formerly thought to move symmetrically in a helical shape. However, a 2020 study by the University of Bristol stated that the tail moves in a more complicated manner, combining asymmetrical standing and travelling waves as well as rotating the entire body to achieve a perceived symmetry.
Sperm centrioles :
Most sperm cells have centrioles in the sperm neck. Sperm of many animals has 2 typical centrioles known as the proximal centriole and distal centriole. Some animals like human and bovine have a single typical centriole, known as the proximal centriole, and a second centriole with atypical structure. Mice and rats have no recognizable sperm centrioles. The fruit fly Drosophila melanogaster has a single centriole and an atypical centriole named the Proximal Centriole-Like (PCL).
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