TEAMWORK, FROM HEAD TO TOE
Human body systems.
Connected functions.
A body system is a group of parts that work together. Their coordinated functions maintain internal balance, respond to the environment and support daily activity.
BODY SYSTEM 01
Nervous system
Receives information and sends messages that coordinate your body.
When you reach for a ball, your eyes send information to your brain. Your brain sends instructions through nerves to the muscles in your arm.
Principal structures
Brain ↗Spinal cord ↗Nerve ↗BODY SYSTEM 02
Circulatory system
Moves blood, oxygen and nutrients around your body.
Your heart pumps blood to your lungs to collect oxygen. Blood then delivers oxygen to body cells and carries carbon dioxide back to your lungs.
Principal structures
Heart ↗Blood ↗Artery ↗Vein ↗Capillary ↗BODY SYSTEM 03
Respiratory system
Brings oxygen in and lets carbon dioxide out.
Your diaphragm contracts to help draw air in. Air reaches your lungs, where oxygen crosses into the blood through the walls of tiny air sacs.
Principal structures
Nose ↗Larynx ↗Trachea ↗Bronchi ↗Lungs ↗Alveoli ↗Diaphragm ↗BODY SYSTEM 04
Digestive system
Breaks food down so your body can use its nutrients.
Teeth break food into pieces, the stomach mixes it, and the small intestine absorbs nutrients. Your blood then carries these nutrients around your body.
Principal structures
Mouth ↗Salivary glands ↗Esophagus ↗Stomach ↗Liver ↗Gallbladder ↗Pancreas ↗Small intestine ↗Large intestine ↗Rectum ↗Anus ↗BODY SYSTEM 05
Skeletal system
Supports your body and protects important organs.
Bones provide a framework. Muscles pull on them through tendons, and joints allow movement.
Principal structures
Skull ↗Ribs ↗Spine ↗Pelvis ↗Femur ↗Joint ↗Cartilage ↗Bone marrow ↗BODY SYSTEM 06
Muscular system
Creates movement and helps keep your posture.
When you bend your elbow, some muscles contract while others relax. Their coordinated pull moves the bones at the joint.
Principal structures
Muscle ↗Tendon ↗Shoulder ↗Arm ↗Leg ↗Diaphragm ↗BODY SYSTEM 07
Integumentary system
Covers and protects your body.
Skin forms a barrier, nerves in the skin notice touch, and sweat helps cool you when it evaporates.
Principal structures
Skin ↗Hair ↗Nail ↗Sweat gland ↗BODY SYSTEM 08
Urinary system
Filters blood, balances fluids and removes urine.
Kidneys make urine, ureters carry it to the bladder, and the urethra provides the path out during urination.
Principal structures
Kidneys ↗Ureters ↗Bladder ↗Urethra ↗BODY SYSTEM 09
Endocrine system
Sends chemical messages called hormones.
Hormones travel in the blood to their target cells. Different hormones help guide growth, energy use and changes during puberty.
Principal structures
Hypothalamus ↗Pituitary gland ↗Thyroid ↗Parathyroid glands ↗Adrenal glands ↗Pancreas ↗Pineal gland ↗Ovaries ↗Testes ↗BODY SYSTEM 10
Lymphatic & immune systems
Return extra fluid to the blood and help defend against germs.
Lymph vessels collect extra fluid from tissues. Lymph nodes filter that fluid, and immune cells help recognize and respond to germs.
Principal structures
Lymph vessels ↗Lymph nodes ↗Spleen ↗Thymus ↗Tonsils ↗Bone marrow ↗BODY SYSTEM 11
Reproductive system
Includes the body parts involved in reproduction.
Bodies develop in different ways. During puberty, hormones help reproductive organs mature. A pregnancy can begin when a sperm cell fertilizes an egg cell, and development continues in the uterus.