The biology of sex is an intricate process that sees the body go through a number of changes and adaptations. There are many reasons why people have sex, from improving intimacy and for pleasure to the chance to conceive. Sex has a number of benefits, such as relieving stress and boosting immunity, burning calories and reducing pain. There are many expectant parents who look forward to the 20 week scan, the scan which tells them the gender of their baby, but what happens to get the baby there? This is more than just ‘the birds and the bees’ – what goes on within the body to create a baby? As an embryo develops, it develops what are known as Wolffian and Mullerian ducts; the Wolffian ducts turn into male sex organs and the Mullerian ducts develop into female sex organs. These organs depend on the presence of a Y chromosome. At week eight, the genitalia begin to develop as well. The external genitals continue to develop after the internal organs have formed, which means in men the testosterone produces a penis and a scrotum, and a lack of testosterone will mean a vagina and labia will form. Such organs develop throughout the pregnancy and will develop further in puberty later in life as well.
From an exterior angle, the male body has two visible sexual organs – the testes and the penis. In terms of primary sexual organs, the testicles are the organs which make sperm and produce testosterone. The testicles are housed outside of the body to keep the temperature cool so as not to damage the sperm. Sperm are often compared to tadpoles in appearance and they use their tails to travel, with the heads containing the genetic material. The penis is made from spongy tissue which expands and contracts, becoming stiff and engorged with blood when the man becomes aroused. This makes it easier for the penis to be inserted into the vagina during sex. Sperm gets mixed with the nutrient-rich fluids from the vesicle in the body to create a fluid known as semen which does three jobs. It provides a watery environment where sperm can swim while they are outside of the body, it provides nutrients such as vitamin C and fructose for the sperm, and it protects the cells by neutralising the acids in the female sexual tract.
The two ovaries in the female body are the counterpart to the male testes. They make the eggs and produce oestrogen, the female sex hormone. The oestrogen leads to the sexual characteristics in the female body, such as breast development, pubic hair, depositing fat in the hips and thighs, and widening the pelvis. Eggs develop in the ovaries and are released into the fallopian tube during ovulation – it’s during this time that fertilisation can take place if sperm can find itself within the body during sex. The fertilised egg can then move down to the womb where it develops. It’s made of spongy material that cushions the egg while it grows. The uterus stretches during pregnancy to hold the baby until it has reached full size and is ready to be born. At the base of the uterus is the cervix, which also widens during labour to allow the baby to come out. The vaginal walls can stretch to accommodate intercourse and childbirth, and the final two glands are found here, where they secrete fluids into the labial folds of skin.
