'There's a huge amount that we don't understand': Why sperm is still so mysterious
20 hours ago Share Save Katherine Latham Share Save
How do sperm swim? How do they navigate? What is sperm made of? What does a World War Two codebreaker have to do with it all? The BBC untangles why we know so little about this mysterious cell.
With every heartbeat, a man can produce around 1,000 sperm – and during intercourse, more than 50 million of the intrepid swimmers set out to fertilise an egg. Only a few make it to the final destination, before a single sperm wins the race and penetrates the egg.
But much about this epic journey – and the microscopic explorers themselves – remains a mystery to science.
"How does a sperm swim? How does it find the egg? How does it fertilise the egg?" asks Sarah Martins da Silva, clinical reader of diabetes endocrinology and reproductive biology at the University of Dundee in the UK. Almost 350 years on from the discovery of sperm, many of these questions remain surprisingly open to debate.
Using newly developed methods, scientists are now following sperm on their migration – from their genesis in the testes all the way to the fertilisation of the egg in the female body. The results are leading to groundbreaking new discoveries, from how sperm really swim to the surprisingly big changes that occur to them when they reach the female body.
No other cell within the body changes its structure, its shape, in such a unique way – Adam Watkins
"Sperm – or spermatozoa – are 'very, very different' from all other cells on Earth," says Martins da Silva. "They don't handle energy in the same way. They don't have the same sort of cellular metabolism and mechanisms that we would expect to find in all other cells."
Due to the huge range of functions demanded of spermatozoa, they require more energy than other cells. Plus sperm need to be flexible, to be able to respond to environmental cues and varying energetic demands during ejaculation and the journey along the female tract, right up until fertilisation.
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