Sperm is a reproductive cell created in the testicles. Males produce millions of these cells each day, but it takes only one sperm to fertilize an egg.
This article outlines what sperm are, where they originate, and the factors affecting their ability to fertilize an egg.
Sperm is the male reproductive cell or gamete. The term “gamete” implies that the cell is half of a whole. When a sperm combines with a female gamete, or egg, it results in a human embryo.
When studying a sperm cell under a microscope, scientists can typically identify the following three parts:
The head
The sperm head contains chromatin, which is the DNA material that makes up chromosomes.
Typically, both the human sperm cell and the human egg cell each contain 23 chromosomes. When the sperm and egg combine, this results in an embryo with 46 chromosomes.
Covering the head of the sperm is a cap that doctors call an acrosome. The acrosome contains proteins that help the sperm penetrate the outer shell of an egg.
The midsection
The midsection of the sperm contains energy producing mitochondria. These specialized structures provide the energy necessary for the sperm cell to move.
The tail
The purpose of the sperm tail, or flagellum, is to allow movement. The tail propels the sperm forward, towards an egg for fertilization.
The testicles are the male reproductive organs responsible for making sperm. They also produce testosterone, which is a sex hormone responsible for many male characteristics.
Spermatogenesis is the process of creating sperm cells. This process begins in the seminiferous tubules within the testicles. These tubules produce sperm cells called spermatocytes.
Spermatocytes undergo several rounds of division to turn the cells into spermatids. Spermatids are young sperm that must grow and mature until they become sperm cells.
According to a 2013 article, the male body takes about
On average, a male produces approximately 73 million sperm cells per milliliter of ejaculate.
Once an individual releases their sperm, they can live in the female vagina for up to
Two key factors that can affect male fertility are sperm count and sperm motility.
Sperm count refers to the number of sperm cells present in male ejaculate. Sperm motility refers to the ability of sperm to move towards an egg.
Sperm count
The testicles produce millions of sperm each day, but this number can vary greatly.
The same research, however, suggests that daily sperm production can vary according to a person’s ethnicity.
The study gives the following average daily sperm production levels for males of the following ethnicities:
- Hispanic: Between 231 million and 398 million sperm per day.
- White: Around 193 million to 318 million sperm per day.
- Chinese: Between 70 million and 173 million sperm per day.
If a person has tried to conceive with their partner for a year without success, a doctor may suggest a semen analysis. This involves the individual ejaculating into a cup or other container. The semen then goes to a laboratory for examination.
A semen analysis assesses the sperm count and the following factors:
- semen volume
- sperm concentration
- sperm motility
- sperm morphology
Some people may have low to no sperm present in their ejaculate. This does not always mean that their testicles do not produce sperm.
The condition, which doctors call azoospermia, can arise from low sperm production or an issue, such as a blockage, that inhibits sperm delivery into the ejaculate.
Sperm motility
Motility is crucial for fertilizing an egg. The egg does not contain cells that allow it to move. Therefore, it is up to the sperm to propel themselves forward towards the egg.
According to a 2015 study, an estimated
Sperm quality and motility will typically decrease as a person ages. Other factors that may affect sperm quality and motility include:
- inactive lifestyle
- excessive alcohol consumption
- smoking cigarettes
- taking artificial steroids, including workout supplements
- use of illegal drugs
- heart disease or heart problems
- prolonged exposure to heat, such as saunas or hot tubs
Modifying certain lifestyle factors could, therefore, help some people to improve their fertility.
Sometimes, people can collect their sperm for use in artificial insemination. These techniques include intrauterine insemination (IUI) and in vitro fertilization (IVF).
IUI involves placing the sperm directly into the female uterus to assist fertilization. IVF involves bringing together the sperm and egg in a laboratory and transferring the growing embryo into the uterus.
To collect a sperm sample, the male ejaculates into a sterile container. A laboratory technician will then take the semen sample for use with IUI or IVF, or freeze it for preservation. The laboratory can later thaw the sample for use.
For cryopreservation, or sperm banking, a person collects samples of their sperm that then undergo rigorous testing for infectious diseases, and genetic conditions, prior to donation.
Sperm cells are male reproductive cells that originate in the testicles. Sperm cells swim to and fertilize a female reproductive cell called an oocyte, or egg.
Two key factors that can affect male fertility are sperm count and sperm motility. Those experiencing fertility issues may benefit from a semen analysis. This test will help to identify any potential sperm issues.
Sometimes, a person may want to provide a sperm sample for use with assisted reproductive technology (ART), including IUI or IVF.
Couples desiring to pursue ART should speak to their doctor for further advice.