Blood is considered a fluid (liquid) connective tissue because it has a matrix and living cells. The matrix is called the plasma which liquid part. The plasma contains proteins, salts, and hormones. Blood flows and transports gases, digested food, hormones and waste materials to different parts of the body. The living cell types are red blood cells (RBC) are also called erythrocytes, white blood cells (WBC) are also called leukocytes and platelets are suspended in the plasma.