Discuss the composition of blood and the main functions of its various components.

Blood is a type of fluid connective tissue composed of a liquid matrix called plasma, and formed elements including red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). 
1. Plasma: Transports water, nutrients, hormones, waste products, and proteins. 
2. Red Blood Cells: Contain hemoglobin and are responsible for oxygen transport. 
3. White Blood Cells: Involved in the body's immune defense, fighting infections. 
4. Platelets: Essential for blood clotting and preventing excessive bleeding.