Re: As blood is a mixture of cells, is it a tissue or an organ?

A tissue is generally defined as a group of similar cells, working together 
to perform a specific function.  An organ is defined as a group of tissues 
working together to perform a more complex function.  This definitions work 
well for the middle school/junior high school level, but as in many other 
cases, may not tell the complete truth.

Blood is generally considered to be a tissue.  There's a lot of information 
out there on the web, but much of it is for medical professionals and, as 
such, is far above the level of the general public.  The best I can do for 
you is to direct you to two Encarta articles, 
 http://encarta.msn.com/find/Concise.asp?z=1&pg=2&ti=761554781
and http://encarta.msn.com/find/Concise.asp?z=1&pg=2&ti=761557840

The different parts of blood don't really work together.  They are found in 
the same place (blood vessels such as arteries and veins) but they act 
seperately.  Hope this answers your question.

Your mad scientist,
S. Kohler