sexual reproduction

Humans reproduce sexually

Requires two parents and the fusion of gametes (sex cells), leading to genetically unique offspring.

Male gamete

Sperm cell produced in the testes.

Sperm cell characteristics

Millions produced, small and streamlined, contains half the normal number of chromosomes (23), contains many mitochondria for energy, has a tail for swimming, and an acrosome to break down the egg's jelly coat.

Female gamete

Egg (ovum) cell produced and matured in the ovaries.

Egg cell characteristics

Contains half the normal chromosome number (haploid), surrounded by a jelly coat for protection, large cell with food stored in the cytoplasm for the developing embryo.

Male reproductive system function

To produce and release sperm cells (ejaculation) and testosterone (male sex hormone).

Testis

Where sperm are produced and testosterone is produced, which plays a major role in body development during puberty.

Scrotum

Bag-like structure holding the testes outside of the body, allowing sperm cells to develop properly at temperatures lower than body temperature (37 degrees).

Sperm duct

Carries sperm from the testes to be released out of the body.

Seminal vesicle

Produces the liquid sperm swim in, called semen, which contains nutrients such as glucose.

Urethra (male)

A small tube that carries urine from the bladder to be excreted out of the body; runs within the penis.

Penis

Contains the urethra which carries both sperm and urine to be released out of the body, controlled by a ring of muscle.

Female reproductive system function

To release eggs and support a growing embryo to a baby.

Ovary

Where the eggs (ova) are made and matured; produces and releases oestrogen, the female sex hormone.

Oviduct

Tubes which carry the eggs from the ovaries to the uterus, lined with ciliated epithelial cells to waft the egg.

Uterus

Also called womb; where the foetus grows and develops during pregnancy, with a thick outer wall for pushing the baby out during birth.

Vagina

Where the penis is inserted during sexual intercourse and the route the baby takes during birth.

Cervix

The narrow structure between the vagina and uterus that supports the baby during pregnancy and forms a barrier to protect from microbes.

Puberty

The stage at which the reproductive organs become mature, with ovaries releasing eggs and testes producing sperm.

Secondary sexual characteristics in girls

Breasts enlarge, hips get broader, increased hair growth under the arms, growth of pubic hair.

Secondary sexual characteristics in boys

Increased muscle growth, penis grows bigger, voice becomes deeper, extra hair growth in pubic regions and on the face.

Adolescence

The stage in the life of a young person during which physical, psychological, emotional, and social changes occur.

Menstrual Cycle

The changes that occur in a woman's uterus over the course of a month, typically taking approximately 28 days.

Menstruation

The process where the uterus lining breaks down and the egg and blood are passed through the vagina, occurring from day 1 to 5 of the cycle.

Ovulation

The release of a single egg from one of the two ovaries, occurring approximately on day 14 of the menstrual cycle.

Fertilisation

The joining of an egg cell and sperm cell where their nuclei fuse to create a zygote with a complete number of chromosomes.

Zygote

The cell formed from the fusion of an egg and sperm, which divides into a ball of cells called an embryo.

Implantation

The process where the embryo buries itself into the lining of the uterus after moving down the oviduct.

Gestation period

The length of time the growing embryo will stay in the uterus, which is around nine months in humans.

Foetus

The term used to describe the developing embryo after it has developed organs and begins to resemble a baby, typically referred to after the 10th week of pregnancy.

Placenta

An organ that develops in the lining of the uterus, attached to the foetus by the umbilical cord, facilitating the exchange of materials between the mother and foetus.

Amniotic fluid

The liquid surrounding the foetus that provides protection and cushions it from bumps.

Umbilical cord

The structure that attaches the foetus to the placenta, allowing the flow of blood and nutrients.

Afterbirth

The placenta and umbilical cord expelled from the body after the birth of the baby.

Birth

The process at the end of pregnancy where the foetus is pushed out through the cervix and vagina, typically around 40 weeks.

Sperm

The male reproductive cells that swim through the cervix and uterus to fertilise an egg.

Cervix

The lower part of the uterus that opens into the vagina, through which sperm must travel.

Oviduct

The tube through which the egg travels from the ovary to the uterus.

Embryo

The early stage of development after fertilisation, before it is referred to as a foetus.

Nutrients

Substances provided to the foetus through the placenta, necessary for growth and development.

Toxic materials

Harmful substances that can cross the placenta and potentially cause damage to the developing foetus.

Mammary glands

Glands in the mother's breasts that produce milk to feed the newborn baby.

Contractions

Powerful muscle movements of the uterus that help push the baby out during birth.

Chromosomes

Structures within cells that contain genetic information; the complete number is restored during fertilisation.

Diffusion

The process by which materials move from a high concentration to a low concentration across a membrane.