Types of blood

Blood has four parts. Red blood cells and plasma make up most of your blood. White blood cells and platelets, sometimes referred to as the buffy coat, account for less than 1% of your blood.

Red blood cells

Red blood cells (erythrocytes) account for 45% of your blood. They carry oxygen throughout your body. They also help to clear waste from your body. These cells:

• Get their distinctive color from the protein hemoglobin. Hemoglobin helps the red blood cells deliver the oxygen other cells need to produce energy.
• Can squeeze through the tiniest sections of your circulatory system. (Your circulatory system includes the network of capillaries, veins and arteries that blood moves through on its journey throughout your body).
• Have a short life span. Red blood cells live for about 120 days before they’re replaced with new cells.

White blood cells

Your white blood cells (leukocytes) account for less than 1% of your blood and are part of your immune system. When invaders such as viruses or cancerous cells launch attacks, your white blood cells move quickly to find and destroy them. White blood cells can move from capillaries into your tissues. There are five types of white blood cells:

• Neutrophils kill bacteria and fungi and remove foreign debris.
• Lymphocytes consist of T-cells, natural killer cells and B-cells that protect against viral infections and produce antibodies that help you fight infection.
• Basophils react to allergens.
• Eosinophils find and destroy parasites and cancerous cells and assist basophils with your allergic response.
• Monocytes find and destroy viruses, bacteria, fungi and protozoa. They also remove damaged cells.

Platelets

Your platelets (thrombocytes) are first on the scene any time your blood vessels are damaged and bleeding. Platelets manage bleeding by forming blood clots that seal damaged blood vessels so you don’t lose large amounts of blood. Platelets:

• Account for less than 1% of your blood. There are tens of thousands of platelets in a single drop of your blood.
• Get their name from how they work in your blood. Platelets are the lightest part of your blood. They form in the shape of plates, flattening themselves against blood vessel walls as plasma and blood cells flow by.
• Have a coat of sticky proteins that act like Velcro®, helping platelets cling to broken blood vessels.

Plasma

Your blood cells and platelets float in your plasma. Plasma is a yellowish fluid that accounts for 55% of your blood. Plasma is your blood’s utility player, covering many bases as it works to keep your body functioning. Some tasks plasma does include:

• Helping to clot blood and defend against invaders.
• Delivering hormones, nutrients and proteins to parts of your body and helping to exchange oxygen and carbon dioxide.
• Removing waste from cells and transporting it to your liver, lungsand kidneys for excretion.
• Maintaining your blood pressure and circulation.
• Regulating body temperature by absorbing and releasing heat.