The four parts of the blood?

Plasma is the liquid part of blood that makes up about 55% of its volume. It is composed of water, electrolytes, proteins, hormones, and waste products.

Red blood cells are also called erythrocytes. They make up about 45% of blood volume and contain hemoglobin, a protein that carries oxygen.

White blood cells are also called leukocytes. They make up less than 1% of blood volume but are essential for fighting infection.

Platelets are also called thrombocytes. They make up less than 1% of blood volume and are essential for blood clotting.