Blood Components

• What is blood?
• Does a blood substitute exist?
• What are the components of blood?
• Circular of information

What is blood?

Whole blood is a living tissue that carries everything that human cells need to stay alive: oxygen, nutrients, chemical regulators, electrolytes, hormones, vitamins and substances that protect against disease. It also collects wastes so that the body can eliminate them. On average, the human body contains five to six litres of blood.

Does a blood substitute exist?

Blood is a unique resource for which modern science has not yet found an artificial substitute. In view of the complexity of its components and the defence mechanisms attributed to it, research scientists are still a long way from discovering a suitable substitute for this precious resource.

Blood must, therefore, be collected from humans.

Québec hospitals depend on the generosity of donors for their blood supply. These donors are individuals who are concerned about sharing the great wealth that circulates in their veins.

Several thousand patients, both children and adults, would not recover their health without blood donations.

In fact, only 3% of the population of Quebecers who are eligible to donate blood actually give this gift of life.

What are the components of blood?

Plasma

Plasma constitutes 55% of total blood volume. Composed of 90% water, salts, lipids and hormones, it is especially rich in proteins (including its main protein albumin), immunoglobulins, clotting factors and fibrinogen.

Plasma performs several functions: transporting blood cells and nutrients; regulating the body’s water and mineral salts; irrigating tissues; providing a defence against infections; and coagulating blood.

The albumin contained in plasma prevents the blood from losing too much water and consistency as it travels through the narrow, water-permeable blood vessels (capillaries). Albumin transports various blood components and nutrients. The immunoglobulins also contained in plasma are antibodies that, along with white blood cells, play an important role in fighting against pathogens. Clotting factors, in combination with platelets, control hemorrhaging.

A deficiency in these proteins can cause various health problems. For example, the lack of albumin can lead to the inability to retain water in the vessels, the lack of immunoglobulins can lead to a decline in the body’s immune defences and a lack of clotting factors can lead to blood clotting anomalies.

Red blood cells, white blood cells and platelets are suspended in plasma.

Red Blood Cells

A drop of blood the size of a pinhead contains approximately 5 million red blood cells (erythrocytes). They are small biconcave disks without a nucleus and get their red colour from an iron-containing protein called hemoglobin. Red cells make up between 37% and 43% of blood volume in women and between 43% to 49% in men. Red blood cells carry oxygen throughout the body.

White Blood Cells

There are between 6,000 and 8,000 white cells per cubic millimetre of blood. White cells, slightly larger than red cells, are also called leukocytes. They purify and protect the body from infections. Once an infection is detected in any part of the body, the while cells move in to fight it.

Platelets

Platelets, or thrombocytes, are smaller than the red and white blood cells. Platelets play a role in blood coagulation and wound healing. When a blood vessel ruptures, platelets combine with fibrin, derived from fibrinogen, to form a clot.