• Choose a category
• All
• Classic-Fiction

Blood also contains several types of white blood cells, which fight infection. Most white blood cells are neutrophils, which attack and surround bacteria and destroy them. Other white blood cells called lymphocytes seek out foreign cells, infectious microorganisms, and other potentially harmful substances in the blood and trigger an immune response in the body. Platelets are cell fragments that enable blood to clot, gathering wherever a blood vessel is injured to begin the blood-clotting process that seals the injury and enables the blood vessel to heal. Proteins in the plasma called coagulation (blood clotting) factors help the platelets to form blood clots.

Basic components of blood

Blood can be broken down easily into its separate parts: plasma, red blood cells, white blood cells, and platelets. Plasma is a yellowish fluid that contains minerals, antibodies (infection-fighting proteins), and blood-clotting factors.

White blood cells

White blood cells protect the body against infection by destroying bacteria and producing antibodies (proteins that fight specific germs recognized by the body). Neutrophils and lymphocytes are two types of white blood cells.

Platelets

Platelets are cell fragments that enable blood to clot, which is essential for wound healing.

Red blood cells

Red blood cells, or erythrocytes, make up about 40 to 45 percent of blood. Red blood cells contain a protein called hemoglobin, which carries oxygen to the tissues.

All blood cells are produced in the bone marrow (a soft tissue inside bone cavities). Lymphocytes are also produced in the lymph glands in the neck, armpits, groin, and other parts of the body. The spleen and lymph glands and the channels and ducts that connect them make up the lymphatic system, which is an important component of the immune system (the body’s natural defenses against disease). When red blood cells and platelets are defective, damaged, or old, they are filtered out of the bloodstream and broken down in the spleen and liver.

The different types of blood disorders include lack of hemoglobin (which causes anemia), clotting disorders (which cause bleeding, bruising, or excessive clotting), cancerous changes in white blood cells (which cause leukemia and bone marrow conditions such as multiple myeloma), and lymphatic system disorders such as lymphoma.

Anemia

The main component of red blood cells is an iron-rich protein called hemoglobin, which combines with oxygen in the lungs, carries it through the bloodstream, and delivers it to tissues. In anemia, the body produces too few red blood cells or destroys red blood cells faster than they can be replaced. In some cases, the amount of hemoglobin in the red blood cells is deficient. All of these problems can lead to a shortage of hemoglobin in the blood, which reduces the blood’s ability to deliver oxygen from the lungs to nourish tissues and return the waste product carbon dioxide from the tissues to the lungs for disposal.

Anemia is the most common blood disorder in the United States, affecting more than 3 million people. The disorder can be temporary or chronic, and mild or severe. Anemia can result from a deficiency of iron or other nutrients, from loss of blood, or from a chronic or inherited disease or condition. Anemia also may be a complication from taking some medications or from undergoing radiation therapy (see page 23) or chemotherapy (see page 23) to treat cancer.

Iron Deficiency Anemia

Iron is an essential component of hemoglobin, the oxygen-carrying protein in red blood cells. In healthy people, iron from old red blood cells is stored in the body and used to produce hemoglobin in new red blood cells. The small amount of iron that is normally lost from the body is replaced by iron absorbed from iron-rich foods such as lean red meat, green leafy vegetables, and whole-grain products. If the body loses more iron than it absorbs, the bone marrow produces fewer and smaller red blood cells, and anemia develops. Iron deficiency anemia is usually not life-threatening,