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What are the main components of human blood?
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blood
Blood sediment in test tubes, showing plasma (clear fluid), red blood cells (red), and the release of hemoglobin into the surrounding plasma (pink).
Human blood is a specialized tissue composed of a liquid matrix called plasma in which various cellular elements are suspended.12
The main components of human blood include:
- Plasma: This clear, yellowish fluid makes up the majority of blood volume. It is approximately 90β92 percent water and contains essential solutes, including electrolytes, proteins (such as serum albumin, globulins, and fibrinogen), hormones, vitamins, and waste products.13
- Red blood cells (erythrocytes): These cells constitute about 45 percent of blood volume. They contain hemoglobin, an iron-rich protein that transports oxygen from the lungs to body tissues and assists in carrying carbon dioxide back to the lungs.14
- White blood cells (leukocytes): These cells are vital to the immune system, defending the body against infections and diseases.15
- Platelets (thrombocytes): These small, nonnucleated components are essential for coagulation, helping to form blood clots to stop bleeding at the site of vascular injury.16
Together, white blood cells and platelets account for less than 1 percent of the total blood volume.1