Sperm cells are remarkable cells. They are small but powerful, and they are highly specialised for their important purpose, which is to fertilise egg cells. Think you know all about sperm? Think again…
Sperm cells, or spermatozoa, were discovered back in 1677 by Antonie van Leeuwenhoek. He was a Dutch microbiologist and is now known as the ‘Father of Microbiology’.
-Sperm or semen?
Sperm and semen do not mean the same thing. Semen, also called seminal fluid, is the fluid which contains sperm cells.
-They are small but powerful
In humans, sperm cells consist of a flat, disc shaped head 5 µm by 3 µm and a tail 50 µm long. So 20 in a row are 1 milimeter long 1 Smith DJ, Gaffney EA, Blake JR, Kirkman-Brown JC. Human sperm accumulation near surfaces: a simulation study. Journal of Fluid Mechanics. 2009. 621: 289-320.
The tail of the sperm cell is called a flagellum. It moves, or flagellates, which propels the sperm cell by whipping in an elliptical cone. It moves at a rate of 1–3 mm/minute in humans. That is equivalent to 1.2 cm per hour and almost 30 cm per day.
-They don”t always swim
Sperm cells are generally not mobile until ejaculation. They only start swimming when they get inside the female reproductive tract. They also have an extra burst of energy which makes them speed up when they get nearer the egg.
-Only one sperm wins the race
Sperm cells race to reach the egg cell. The winner fuses with the egg cell and releases enzymes into the outer layer of the egg, called the zona pellucida. This stops the egg from binding with any more sperm cells. It is important that only one sperm fertilises the egg to ensure that the correct amount of genetic material is present to produce healthy cells.
-Men produce lots of sperm
The average man makes a staggering 1,500 sperm cells per second 2 How A Man Produces 1500 Sperm In A Second. National Geographic. 2018. This is because fertilisation is an inefficient process. A man produces many sperm cells to increase the likelihood of just one sperm cell successfully fertilising an egg cell. This developed as an evolutionary advantage, as men who produced more sperm than their competitors were more likely to pass their genes on to the next generation.
-Quantity but not quality?
The quality of human sperm is surprisingly poor in comparison to other mammals 3 Aitken RJ, Sawyer D. The human spermatozoon- not waving but drowning. Advances in Experimental Medicine and Biology. 2003. 518:85-98. In fact in fertile men, up to 85% of ejaculate may consist of abnormal sperm. Furthermore research has shown that the sperm counts of men in Western countries have fallen over the last 40 years by more than 50% 4 Men’s Sperm Counts Are Down Worldwide: Study. Time. 2017. Scientists believe that lifestyle factors are to blame including smoking, obesity and stress.
The technique of sperm freezing and storage (also known as sperm banking) was developed in the 1950s. However it actually originated in 1776 when an Italian priest called Lazaro Spallanzani recorded the effect of snow on human sperm.
-Longest storage time
The longest reported successful storage time for human sperm is 40 years 5 Szell AZ, Bierbaum RC, Hazelrigg WB, Chetkowski RJ. Live births from frozen human semen stored for 40 years. Journal of Assisted Reproduction and Genetics. 2013. 30(6):743-744. Scientists can preserve the sperm for such long periods of time because the low temperatures freeze the chemical reactions in the cells.
-Not all survive
Unfortunately not all the sperm cells will survive the process of freezing and thawing.
-No side effects
There are no side effects for men who undergo sperm freezing. Furthermore, babies produced from frozen sperm are just as healthy as those produced from fresh sperm.
How to produce the best sperm
– Real sex is better
Sperm samples in sexual intercourse contain 70-120% more sperm. Furthermore these sperm cells have higher motility in comparison to sperm samples obtained via masturbation. Sexual intercourse also generates a 25–45% increase in ejaculate volume, mainly by increased prostate secretion. This intercourse advantage is even greater for men with oligospermia.
-Boxers are best
Boxer shorts are better for sperm quality than tighter fitting underwear. The main reason for this is temperature. Higher temperatures can be harmful for sperm cells.
To ensure the best all round sperm quality, it is important to minimise exposure to toxins. This means staying away from nicotine, alcohol, and processed foods for a minimum of three months.
-Take a supplement
Men should make sure they include the proven male fertility micronutrients in their diet. The most convenient and effective way to do this is to take a male fertility supplement.
Dr. Jones is an experienced consultant in assisted reproduction.
He has worked as a Fertility specialist at Kingston Hospital Assisted Conception and nearly 10 years experience of working in Obstetrics and Gynaecology across hospitals in the UK.
He completed his Masters in Assisted Reproduction Technology and then his PhD, from Imperial College London. Dr. Jones main areas of interest are Single Embryo Transfer, Endometriosis, PCOS and Implantation failure in IVF patients. He is a member of the British Fertility Society and an associate member of the Royal College of Obstetrics and Gynaecology.
- 1Smith DJ, Gaffney EA, Blake JR, Kirkman-Brown JC. Human sperm accumulation near surfaces: a simulation study. Journal of Fluid Mechanics. 2009. 621: 289-320
- 2How A Man Produces 1500 Sperm In A Second. National Geographic. 2018
- 3Aitken RJ, Sawyer D. The human spermatozoon- not waving but drowning. Advances in Experimental Medicine and Biology. 2003. 518:85-98
- 4Men’s Sperm Counts Are Down Worldwide: Study. Time. 2017
- 5Szell AZ, Bierbaum RC, Hazelrigg WB, Chetkowski RJ. Live births from frozen human semen stored for 40 years. Journal of Assisted Reproduction and Genetics. 2013. 30(6):743-744