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Unlock This CourseAll living things need to reproduce to continue their species. Humans have evolved amazing adaptations in their reproductive systems to make this possible. These adaptations ensure that sperm and egg cells can meet, fertilise and develop into a new human being.
The reproductive systems of males and females have different but complementary roles. Males produce and deliver sperm cells, whilst females produce egg cells and provide a safe environment for a baby to develop.
Key Definitions:
The male reproductive system is designed to produce millions of sperm cells and deliver them to the female reproductive system. Key adaptations include external testes for temperature control and specialised tubes for sperm transport.
The female reproductive system produces egg cells and provides the perfect environment for fertilisation and pregnancy. It includes adaptations like the fallopian tubes for egg transport and the uterus for baby development.
The male reproductive system has several clever adaptations that help ensure sperm cells can be produced successfully and reach their destination.
The testes are where sperm cells are made. They have some fascinating adaptations that help them do their job properly.
Testes hang outside the body in the scrotum because sperm production needs a temperature about 2°C cooler than normal body temperature. This external position is a crucial adaptation.
Inside each testis are thousands of tiny coiled tubes called seminiferous tubules. These provide a huge surface area for sperm production - about 250 metres of tubes in each testis!
Unlike females who are born with all their eggs, males produce fresh sperm continuously from puberty onwards. This takes about 74 days from start to finish.
Sperm cells are perfectly designed for their mission - to swim through the female reproductive system and fertilise an egg cell.
Head: Contains the nucleus with genetic material and enzymes to break through the egg's protective layer. Middle section: Packed with mitochondria to provide energy for swimming. Tail (flagellum): Whips back and forth to propel the sperm forward at speeds up to 25cm per hour.
The female reproductive system has evolved remarkable adaptations to produce egg cells, enable fertilisation and support a developing baby for nine months.
The ovaries are where egg cells mature and are released. They contain some incredible adaptations for this vital function.
Females are born with all the egg cells they'll ever have - about 1-2 million! These are stored in follicles within the ovaries. By puberty, this number has dropped to about 400,000 and only about 400 will actually be released during a woman's reproductive years.
The ovaries work on a roughly 28-day cycle, releasing one mature egg each month. This timing is controlled by hormones and ensures the female body is prepared for potential pregnancy.
These tubes connect the ovaries to the uterus and have special features to help egg and sperm cells meet.
The inside of fallopian tubes is lined with tiny hair-like structures called cilia. These beat in waves to help move the egg cell towards the uterus. The tubes also have muscular walls that contract to assist this movement.
The widest part of the fallopian tube is where fertilisation usually occurs. This gives sperm and egg the best chance of meeting and the tube's shape helps guide them together.
The uterus is specially adapted to nurture a developing baby for nine months of pregnancy.
The uterus wall has three layers: the outer protective layer, a thick muscular middle layer that can stretch enormously during pregnancy and contract powerfully during birth and an inner lining (endometrium) that thickens each month to prepare for a potential pregnancy. If pregnancy doesn't occur, this lining is shed during menstruation.
Egg cells are the largest cells in the human body and have several adaptations that help ensure successful fertilisation and early development.
Egg cells are about 0.1mm across - large enough to see with the naked eye! They're packed with nutrients and proteins needed for the first few days of development after fertilisation, before the embryo can get nutrients from the mother.
Egg cells are surrounded by protective layers including the zona pellucida. This acts like a selective barrier - it helps the right sperm get through whilst preventing others from entering once fertilisation has occurred.
Both male and female reproductive systems rely on hormones to function properly. These chemical messengers coordinate the complex processes of reproduction.
Testosterone is the main male hormone, produced in the testes. It's responsible for sperm production and the development of male characteristics during puberty.
The female reproductive system uses several hormones working together in a monthly cycle.
Produced by the ovaries, oestrogen helps eggs mature and prepares the uterus lining for potential pregnancy. Levels rise in the first half of the menstrual cycle.
Also made by the ovaries, progesterone maintains the uterus lining after ovulation. If pregnancy occurs, progesterone levels stay high to support the developing baby.
These hormones from the brain control the ovaries. FSH helps eggs mature, whilst LH triggers ovulation - the release of a mature egg from the ovary.
During ejaculation, males release 200-500 million sperm cells, but only one will fertilise the egg. The journey from the vagina to the fallopian tubes takes sperm about 30 minutes to several hours. A woman's egg cell can only be fertilised for about 12-24 hours after ovulation, whilst sperm can survive in the female reproductive system for up to 5 days.