Composition of Blood

Whole blood consists of the blood plasma, a fluid extracellular matrix, and formed elements, including cells and cell fragments.

Blood plasma, which makes up about 55% of total blood volume, is a yellowish fluid. It is predominantly water dissolved with vital substances, such as electrolytes and proteins.

It also acts as a medium for carrying nutrients, enzymes, antibodies, hormones, gasses, and blood cells.

Red blood cells, white blood cells, and platelets, collectively known as the formed elements, make up 45% of the blood's volume.

The red blood cells or erythrocytes comprise about 99% of the formed elements; their percentage in the total volume of a blood sample is known as the hematocrit.

The mature erythrocytes are anucleated and contain hemoglobin — a specialized protein that binds and transports oxygen and carbon dioxide between lungs and tissues.

The white blood cells or leukocytes are a group of nucleated cells involved in immune responses.

Lastly, platelets are enucleated cell fragments essential for clotting and repairing damaged blood vessels.