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Human Body Systems
Unit Notes
Levels of organization in the body:
cells

tissues

organs

organ systems

organism
 Important tissues and their functions:
Blood: transports materials throughout the body
Bone: supports and protects body and organs
Muscle: helps the body to move; aids in circulation, digestion, and respiration
Nerve: carries messages throughout the body
Skin: covers and protects the body; excretes wastes
 Important organs and their functions:
Heart: pumps blood
Kidneys: remove wastes from the blood
Lungs: exchange gases with the environment
Stomach: breaks down food by physical and chemical means
Brain: controls thinking and voluntary actions
 Human body systems and their functions:
Skeletal: supports body, protects internal organs
Muscular: moves organs and body parts
Nervous: controls body activities; carries and interprets messages
Endocrine: regulates body activities with hormones
Digestive: breaks down food into a usable form
Circulatory: transports needed materials to cells and carries away wastes
Respiratory: exchanges gases with the environment
Excretory: removes wastes from the body
Reproductive: produces offspring
Examples of organs
or parts
skull, ribs
arm/leg muscles
brain, spinal cord
adrenal glands
stomach, intestines
heart, arteries, veins
lungs, bronchi
kidneys, lung, skin
ovaries, testes
* The most important thing for you to understand about the human body systems is that they work
together. For example, the digestive system breaks down food, but those nutrients rely on the
circulatory system to get them to all the cells and the wastes from the use of that food is removed from
the body by the excretory system. All of these systems are regulated by the endocrine system.