Although sometimes used in error as interchangeable terms, the words sperm and semen refer to distinctly different, yet related, objects. The primary difference between sperm and semen is that sperm are the actual sex cells, whereas semen is the fluid in which the sperm are located. Both of these are necessary for the successful reproduction of human beings.
Sperm are male reproductive cells, which merge with their female counterpart, the egg, to instigate the fertilization process that is eventually responsible for reproduction. The human sperm cell is haploid, meaning it contains half the chromosomes of a typical cell. This enables the combination of the sperm and the egg, also haploid, to fulfill the 46 chromosomes typical of a diploid cell.
Generated in the testes, sperm take months to fully mature. They are composed of three primary regions, consisting of a head, a midpiece, and a tail. The head contains genetic material and is also designed in a manner that enables it to penetrate the female egg, whereas the midpiece is home to the organelles that allow energy production within the sperm. The tail is primarily functional as a means for locomotion, an important characteristic for navigating the relatively viscous semen.
There are some species that utilize nonmotile sperm in reproduction, and such organisms likely do not require the mobilization of sperm. Unlike the sperm, the semen is produced outside of the testes by the seminal vesicle located in the pelvic region of humans. Sperm and semen conjoin later to become the matter of reproduction.
The composition of semen tends to vary based on the source, and that person's biological and lifestyle factors may contribute to the disparity of seminal fluid among human males. Typically speaking, the most common component of semen is a mixture of amino acids, enzymes, and fructose combined with phosphorylcholine, proteins, and vitamin C, among other materials. This mixture generally is responsible for 65% to 75% of seminal volume.
The other 25% to 35% of semen is made up of three different categories of components. The first category, responsible for 2% to 5% of semen are the collection of sperm cells. About 25% is made up of an acidic blend including zinc, citric acid, and acid phosphatase. Lastly, less than 1% of semen is made by the bulbourethral glands, which add galactose and mucus and serve to increase mobility. All of these components of sperm and semen are necessary to create the proper environment for successful reproduction.