Advertisement Upgrade to remove ads

Circulatory, Respiratory, and Excretory Systems.


blood vessels that carry blood away from the heart


tiny, thin-walled blood vessels that allow the exchange of gases and nutrients between the blood and the cells of the body


blood vessels that carry blood back to the heart


flaps of tissue that open and close to allow the flow of blood in one direction only. The heart's valves are located at the entrances and exits of its chambers


multi-chambered, muscular organ that pumps blood throughout the body


small group of cardiac muscle cells in the right atrium that "set the pace" for the heart as a whole; also known as the sinoatrial node


the liquid part of blood

Red Blood Cell

A cell in the blood that takes up oxygen in the lungs and delivers it to cells elsewhere in the body


fragment of a blood cell originating in the bone marrow that is involved in blood clotting

White Blood Cells

A blood cell that functions in defending the body against infections and cancer cells


a condition in which an artery wall thickens as a result of the buildup of fatty materials


The process by which oxygen is taken in through the lungs and carbon dioxide is released out from the lungs.

External Respiration

Exchange of gases between the lungs and the blood

Internal Respiration

exchange of gases between the blood and the cells of the body


the windpipe


either of the two main branches of the trachea


either of two saclike respiratory organs in the chest of vertebrates


tiny air sac at the end of a bronchiole in the lungs that provides surface area for gas exchange to occur


either of two bean-shaped excretory organs that filter wastes (especially urea) from the blood and excrete them and water in urine


waste product formed in the liver, filtered out of the blood by the kidneys, and excreted in urine

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again


Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording