Reproductive system

The reproductive system is a special group of body parts that helps living things make new life. It includes many important pieces, like organs inside the body, as well as fluids, signals called hormones, and special chemicals known as pheromones. These all work together to allow animals and plants to create offspring.

Unlike most body systems that work the same in every individual, the reproductive system often looks quite different depending on whether the organism is male or female. These differences are what allow two individuals to combine their genetic material, creating new life with a mix of traits from both parents. This mixing can help the new offspring be healthier and better suited to survive in the world.

For humans specifically, you can learn more by visiting the page about the Human reproductive system. The organs involved in this process are important parts of the body, and they work with many other chemicals and signals to make reproduction possible.

Animals

See also: Sexual reproduction § Animals

Further information: Sex organ § Animals

In mammals, the main parts of the reproductive system include the outside parts (like the penis and vulva) and several inside parts, such as the organs that make eggs and sperm (called gonads, which are testicles and ovaries). Diseases of this system are common, especially infections that spread easily.

Most other animals with backbones have similar systems made of gonads, tubes, and openings. However, each group of animals has its own unique ways of reproducing and physical traits.

Vertebrates

Animals with backbones all share some basic parts of their reproductive systems. They all have organs that make eggs or sperm, called gonads. In females, these are linked by tubes to an opening, usually the cloaca or vagina.

Humans

Main article: Human reproductive system

Human reproduction happens when a man and a woman have sex. The man's semen, which contains sperm, is released into the woman's vagina. The sperm travel to meet the egg in the uterus or fallopian tubes. If they join, this starts the development of a baby inside the uterus for about nine months, called pregnancy. The baby is born when the uterus contracts and the cervix opens.

The female reproductive system has two main jobs: making egg cells and protecting and nourishing a baby until it is born. The male reproductive system has one main job: making and releasing sperm. Humans have clear differences between males and females in their reproductive organs and other body traits.

Male

Main article: Male reproductive system

The male reproductive system includes organs mostly outside the body that help make and deliver sperm. The main organs are the testicles, where sperm are made, and other parts that store and mix sperm with fluids. These include the seminal vesicles, prostate, and vas deferens. Other organs help with the act of reproduction, like the penis and urethra.

Male bodies also show traits such as more muscle, deeper voice, body and facial hair, broad shoulders, and an Adam's apple. A key hormone in men is testosterone.

Female

Main article: Female reproductive system

The female reproductive system includes organs mostly inside the body that help make eggs and support a developing baby. The main parts are the vulva (which includes the labia, clitoris, and urethra), the vagina, the uterus, and the ovaries. The breasts help with feeding a baby after birth but are not always considered part of the reproductive system.

The vagina connects to the uterus through the cervix, and the uterus connects to the ovaries through the fallopian tubes. Each ovary holds many eggs. About every 28 days, a hormone causes an egg to mature and leave the ovary through the fallopian tube. If sperm meets the egg, it can start a baby. If not, the uterus lining and the egg are shed through menstruation. If the egg is fertilized, it attaches to the uterus lining and begins to develop.

Other mammals

Main article: Mammalian reproductive system

Most mammals have systems much like humans, but there are some differences. For example, many male mammals have a penis stored inside their bodies until they use it, and many females do not have permanent breasts like human women. Marsupials, like kangaroos, have unique systems where females have two vaginas and males have a two-part penis. Their babies develop in a pouch on the mother's belly.

Dogs

Main article: Canine reproduction

In dogs, both males and females reach maturity between 6 and 12 months old, though some large breeds may take longer.

Horses

Main article: Equine anatomy § Reproductive system

The mare's system controls pregnancy, birth, and nursing, as well as her cycle and mating behavior. The stallion's system controls his behavior and physical traits.

Even-toed ungulates

Birds

Main article: Bird anatomy § Reproductive system

Male and female birds have a cloaca, which is an opening for eggs, sperm, and waste. They mate by pressing their cloacae together. Female birds usually have only one functional ovary. Birds are known for caring for their young.

Reptiles

Main article: Reptiles § Reproduction

Reptiles are mostly different in appearance between males and females and have internal fertilization through the cloaca. Some lay eggs, while others give birth to live young. Male reptiles often have special organs for mating.

Amphibians

Main article: Amphibian § Reproduction

Most amphibians lay eggs in water, where they are fertilized outside the body. Some have internal fertilization. All have paired organs for making eggs or sperm, linked to the cloaca.

Fish

Main article: Fish reproduction

Fish have many ways of reproducing. Most lay eggs that are fertilized outside the body, with females releasing eggs and males releasing sperm over them. Some fish have special fins to help with internal fertilization, and a few give birth to live young. Fish have either ovaries or testicles.

Invertebrates

See also: Reproductive system of gastropods and Reproductive system of planarians

Invertebrates have many different ways of reproducing, but they all lay eggs. Besides cephalopods and arthropods, most have fertilization outside the body.

Cephalopods

Main article: Cephalopod § Reproduction and life cycle

All cephalopods are different in appearance between males and females and lay eggs. Most have the male place gametes inside the female to fertilize eggs. Male cephalopods have one testicle. The female has glands that help develop the egg.

In many unshelled male cephalopods, a special arm called a hectocotylus is used to transfer sperm to the female.

Insects

Main article: Insect reproductive system

Most insects lay eggs. Females have ovaries to make eggs, and males have testes to make sperm. During mating, sperm is passed to the female and stored until the eggs are fertilized and laid.

Arachnids

Main article: Arachnids § Reproduction

See also: Opiliones penis

Arachnids may have one or two organs for making sperm or eggs, located in the abdomen. Males usually give sperm to the female in a package. They often have special courtship behaviors. Arachnids lay yolky eggs, and some scorpions give birth to live young.

Plants

Main article: Plant reproductive morphology

Further information: Sex organ § Plants

Flowers are the special parts of many plants that help them make new plants. They are very different and have many ways to reproduce. Even plants that don’t have flowers, like mosses and ferns, have their own ways to make new plants. How these plants reproduce depends on their shape and the environment around them. A scientist named Christian Konrad Sprengel learned that when flowers make new plants, it involves both living things and things that are not alive, like wind or insects, in a process called pollination.

Fungi

Main article: Fungi § Reproduction

Further information: Sex organ § Fungi

Fungi have many ways to reproduce, showing how different they can be. Some fungi can use more than one way to make new fungi. This might happen in two different stages during their life. The environment can cause changes that help them make special parts for making more fungi, either through ways that involve mixing genes or ways that do not. These special parts help spread tiny pieces called spores to grow new fungi.