River of Life: Blood Sustains & Protects
The components of a complex fluid. Our blood is composed of many different components, the largest categories being red and white blood cells (blood-clotting platelets are another key component) and the liquid portion known as blood plasma. A Complete Blood Count (CBC) includes several of the most basic, yet important, measurements of these components.
Red Blood Cells, also called erythrocytes or RBCsNamed for their brilliant color (provided by the iron-rich hemoglobin), RBCs are in many ways the powerhouse component of the blood, accounting for about 40-45 percent of its volume. The shape of a red blood cell is a double concave disk, similar to a donut with a thin, flattened center instead of a hole. READ MORE
There are 20 to 30 trillion red blood cells circulating through the body of an adult. Individual red blood cells live about 100 days, which means that about 2 million die (and an equal number replaced) every second. Production of red blood cells is controlled by erythropoietin, a hormone produced primarily by the kidneys. Red blood cells start as immature cells in the bone marrow and after approximately seven days of maturation are released into the bloodstream.
Red cells contain a complex, iron-containing protein called hemoglobin (it is the iron that makes red blood cells red) that enables RBCs to carry oxygen from the lungs to cells in tissues throughout the body. One red blood cell can contain 250 million hemoglobin molecules. The total amount of iron in an adult body is 5-6 grams, a bit less than the weight of 2 pennies. Hemoglobin is found in the red blood cells of all vertebrates, except fish; it is also found in some invertebrates.
Anemia results when there are too few red blood cells circulating in the bloodstream to deliver adequate oxygen to body tissues. There are different types and causes of anemia, including malnutrition, chronic bleeding, and diseases that result in red blood cells either being destroyed too quickly or produced too slowly. Anemia can be temporary or long term, and it can range from mild to severe. Some types of anemia can be treated through diet or iron supplements; in other cases, however, it is the first sign of a serious condition. Bone marrow may produce too few red blood cells because of chemotherapy or radiation therapy, exposure to toxins, or autoimmune disorders; kidney disease, diabetes, tuberculosis or HIV can also cause long-term decreased production of RBCs.
Anemia (of all types) affects 2 billion people worldwide, or about 30% of the world’s population. Most common causes are iron deficiency, malnutrition and blood loss from parasites. In the U.S. about 8% of the population suffers from anemia, with rates in children more than twice that. LESS
White blood cells, also called or leukocytes, or WBCsWhite blood cells are in the front lines in the fight against harmful viruses, bacteria and even fungus. A white blood cell count is an important measure of this key component of the immune system; when the body is under attack, more WBCs are produced. Other factors, however, may also affect WBC counts, including leukemia, allergies, chemotherapy, and radiation. READ MORE
White blood cells protect the body from infection. There are 5 main categories of white blood cells and, like red blood cells, all are produced from stem cells in the bone marrow. Different white blood cells have specialized immune functions and are activated in response to different conditions and triggers (certain WBCs, for example, are able to ingest harmful foreign particles, including pathogens, in a process called phagocytosis).
Levels of WBCs can be depressed by many different factors. One of the most common reasons is cancer treatment. Both chemotherapy and radiation therapy cause a decrease in the production of WBCs. (Exposure to radiation from a nuclear power plant accident will do the same.) Bone marrow failure can also reduce the number of WBCs.
Too many WBCs can be caused by tissue damage, such as burns, leukemia, or infections. Pregnancy, especially in the final month and during labor, may be accompanied by higher white blood cell counts. Newborns and infants also usually have higher WBC counts. Smoking or severe or emotional stress can also result in higher WBC counts. LESS
Blood plasma, the river that nourishes the bodyblood cells are suspended in a liquid mixture called blood plasma. Plasma contains many substances in suspension or solution, including nutrients, waste products, and special clotting factors, as well as hormones, and chemical messengers such as hormones, and other essential compounds that circulate throughout the body. READ MORE
Red and white blood cells may be the star players in the blood, but they have an incredibly important cast of supporting characters. One of them are the clotting agents called platelets. Unlike RBCs and WBCs, platelets are not actually cells but rather small fragments of cells. Platelets help the blood clotting process by gathering at the site of an injury, sticking to the lining of the injured blood vessel, and forming a platform on which blood coagulation can occur. The clotting factors cover the wound and prevent blood from leaking out; they also form the initial scaffolding upon which new tissue forms, an essential part of healing. A higher than normal number of platelets can cause unnecessary clotting, which can lead to strokes and heart attacks; lower than normal levels of platelets can lead to extensive bleeding. LESS