A group of organs that work together to perform a complex function. There are 8 organ systems.
- Circulatory system: includes the heart and blood vessels (arteries and veins), as well as the blood itself.
- Respiratory system: contains the lungs, trachea (windpipe) and all of the airways of the respiratory tree.
- Integumentary system: skin, which includes all the sweat glands, hair follicles and plenty of nerves.
- Endocrine system: all the glands that secret hormones into the bloodstream.
- Gastrointestinal system: affectionately known as the gut, which includes all the organs that carry food from where it comes in to where it goes out.
- Musculoskeletal system: the skeleton and all the muscles, tendons and ligaments that are attached to it.
- Nervous system: includes the brain and spinal cord, plus all the nerves that are connected to both of these organs.
- Reproductive system: the only system that is split into two parts. Half of us have a penis and testicles while the other half has a vagina, uterus and ovaries.