In short:
blood > liver > blood
(less urea) > liver > (more urea)
blood > muscles > blood
(more glucose) > Muscles > (less glucose)
blood > kidney > blood
(more urea) > kidney > (less urea)
blood > small intestines > blood
(less glucose) > Small intestines > (more glucose)
blood > lungs > blood
(less oxygen) > lungs > (more oxygen)
*remember:
- as blood moves thru out the body it will lose glucose as it is needed in all cells for cellular respiration
- kidneys remove more than just urea, it also removes excess water/vitamins/minerals and salt.
- in the process of blood moving thru the lungs, it will remove carbon dioxide and take on oxygen. its a two way process - rather than just the simplistic "More oxygen" model i provided.
- remember all the organs that will be asked about and remember the products that will be removed. at the very least remember the MAIN product that will be removed or added depening on the organ.