(1) Blood is a constant ly circulating fluid providing the body with nutrition, oxygen,and waste removal. Blood is mostly liquid, with numerous cells and proteins suspended in it, making blood “thicker”than pure water. The average person has about 5 liters(more than a gallon) of blood. Blood is considered a connective tissue for two basic reasons: (1)embryologically, it has the same origin (mesodermal) as do the other connective tissue types and (2) blood connects the body systems together bringing the needed oxygen,nutrients, hormones and other signalling molecules,and removing the wastes.