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Integumentary system
Function: Protects the body from the outside world and keeps moisture inside. Helps regulate body temperature. Contains sense receptors for temperature, pain, and touch.
Parts: Skin, sweat glands, hair, and fingernails.
Respiratory system
Function: Inhales oxygen and allows it to be dissolved into the bloodstream. Removes carbon dioxide from the bloodstream and exhales it.
Parts: Nose, larynx, trachea, bronchi, lungs, and diaphragm (the muscle that works the lungs).
Skeletal system
Function: Provides shape, support, and protection to the body, while allowing it to move. Blood cells are also produced in the marrow of bones.
Parts: Bones, cartilage, and joints (ligaments and tendons). Fibroblasts are the main cells in dense connective tissue that makes up ligaments and tendons. Fibroblasts secrete collagen and elastic fibers.
Nervous system
Function: Controls and coordinates body functions. Receives signals, processes information, and transmits responses to organs.
Parts: Brain, spinal cord, and nerves.
Digestive system
Function: Breaks down food, absorbs its useful substances, and gets rid of the waste. The useful substances—or nutrients—are used by cells throughout the body for energy and building materials.
Parts: The mouth, esophagus, stomach, liver, small intestine, large intestine, rectum, and anus.
Muscular system
Function: Moves the body, moves materials within the body, and generates heat.
Parts: Skeletal muscles, which are attached to bones and move the body around. (Smooth muscle tissue and cardiac muscle tissue are included in other systems).
Cardiovascular system
Function: Delivers oxygen and nutrients to cells throughout the body. It also carries waste materials away from all the cells. It is also the main distribution system for all sorts of chemical signals, and for white blood cells that travel around the body fighting infectious diseases. The cardiovascular system also helps regulate body temperature, by controlling how much blood flows near the body’s surface at different times.
Parts: The heart, blood vessels, and blood. (Weird fact: blood is considered a connective tissue, even though most tissues are solid.)
Lymphatic system
Function: Takes fluid that has leaked out of blood vessels and returns it to the cardiovascular system. As this lymph fluid filters through the system, white blood cells also check it for signs of infection, and manage the body’s immune response to disease. (Sometimes scientists identify the immune system as a separate system.)
Parts: Lymph vessels, lymph nodes, tonsils, thymus, and spleen.
Urinary system
Function: Removes excess fluid and many dissolved waste products from the body.
Parts: Kidneys, ureters, bladder, and urethra.
Endocrine system
Function: Regulates and controls growth, development, and various body functions by releasing chemical signals called hormones into the bloodstream.
Parts: Various glands throughout the body, including the pituitary, adrenal, and thyroid glands; and also ovaries in women and testes in men.
Reproductive system
Function: Produces children through sexual reproduction.
Parts: Vagina, uterus, and ovaries, or penis and testes.
