Circulatory system

How to measure age of blood cells

See http://www.fda.gov/cber/minutes/pathtrans080802.pdf page 88.
Biotin labels are also used.

Measuring Blood pressure:
http://www.bpassoc.org.uk/information/measured.htm

How it works
http://science.howstuffworks.com/question146.htm - nice animation of heart working

How do you know when to change your pacemakers batteries?
http://www.healthyhearts.com/pacemaker.htm

Circulatory system
http://www.getbodysmart.com/ap/circulatory/menu/circulatory.html
http://w3.dwm.ks.edu.tw/bio/activelearner/42/ch42intro.html