Almost all animals reproduce sexually. This means that two animals, one male and one female, come together to mate. The male's sperm fertilizes the female's egg in order to create a fertilized embryo that will grow into that animal. This is how humans reproduce as well.
The components of semen and sperm ensure that the sperm itself will survive, have the necessary DNA to fertilize the female's egg and be able to survive the journey from the sperm's starting point (the testicles) to the end point (inside the female's reproductive organs to fertilize the egg).
According to MedicineNet, you define semen as the fluid that is ejaculated from the male's penis during orgasm. It's also referred to as seminal fluid and sperm, and people often use all of these terms interchangeably. While sperm is a primary component of semen, it isn't the only component.
Semen is a combination of sperm cells and various fluids that are generally referred to as seminal fluids.
Sperm is the primary component of semen. Sperm are the male gametes, also known as sex cells. that are produced in the testicles. The testicles are also called "gonads" and are found in male animals, including humans.
The testicles consistently produce sperm from when they hit puberty (or sexual maturity in the case of animals) throughout their entire life. Each ejaculation of semen can range between 2 to 5 milliliters of semen. And since each milliliter of sperm on average contains between 40 and 60 million sperm cells, that means that each ejaculation can total to 300 million sperm.
Sperm cells look like small tadpoles. They consist of a head that contains the haploid DNA used to fertilize the egg, the flagella tail that allows the sperm to "swim" to their destination, and the mid-piece that connects the tail to the head. The mid-piece also contains the sperm cell's mitochondria that is necessary to give the sperm power and energy to reach the egg.
Despite millions of sperm in each ejaculation, sperm cells only account for about 2-5 percent of semen. The rest is made up of fluids that come from various glands.
About 70-80 percent of the components of semen come from the seminal vesicles. These two glands are situated right near the bladder and provide what's appropriately called seminal fluid. Within this fluid are proteins, ascorbic acid, amino acids, potassium, phosphorus and, mostly, fructose.
The fructose is the key component since this is the sugar that gives the sperm the energy they need to make their way to the female's egg. Seminal fluid also contains hormones called prostaglandins. These hormones help the sperm survive inside the female reproductive tract that would normally react against sperm since the body detects it as a foreign invader.
About 25-33 percent of semen is made by the prostate gland. The fluid made by the prostate gland contains the following components:
- Citric acid
- Acid phosphate
Zinc is the one to take note of here. Zinc helps keep the DNA found in sperm stable until it reaches the egg. The potassium and magnesium are also essential since this is what allows the sperm's tail to move, which propels the sperm through the reproductive tract until it gets to the egg.
Bulbourethral and Urethral Glands
A very small amount of fluid is also supplied by the bulbourethral and urethral glands, which amounts to 1 percent (at most) of semen. This fluid "leaks" out of the penis when the male is aroused and adds to the liquid/mucus that makes up semen. It has a few different purposes.
First, the liquid pushes out any urine still in the urethra. This helps the semen flow smoothly and makes sure that there is proper pH and nutrient levels in the semen that could be affected by leftover urine.
The female reproductive tract is also slightly acidic, which would usually kill sperm. The fluid produced by these (and the other) glands helps to neutralize the environment to allow the sperm to survive. This fluid is also lubricating, which helps during intercourse and helps keep the semen liquefied to allow the sperm to swim.
About the Author
Elliot Walsh holds a B.S in Cell and Developmental Biology and a B.A in English Literature from the University of Rochester. He's worked in multiple academic research labs, at a pharmaceutical company, as a TA for chemistry, and as a tutor in STEM subjects. He's currently working full-time as a content writer and editor.