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BLOOD >> What is Blood?

Blood is the most commonly tested part of the body, and it is truly the river of life. Every cell in the body gets its nutrients from blood.

Blood is a mixture of two components: cells and plasma. The heart pumps blood through the arteries, capillaries and veins to provide oxygen and nutrients to every cell of the body. The blood also carries away waste products.

The adult human body contains approximately 5 liters (5.3 quarts) of blood; it makes up 7 to 8 percent of a person’s body weight. Approximately 2.75 to 3 liters of blood is plasma and the rest is the cellular portion.

Plasma is the liquid portion of the blood. Blood cells like red blood cells float in the plasma. Also dissolved in plasma are electrolytes, nutrients and vitamins (absorbed from the intestines or produced by the body), hormones, clotting factors, and proteins such as albumin and immunoglobulins (antibodies to fight infection). Plasma distributes the substances it contains as it circulates throughout the body.

The cellular portion of blood contains red blood cells (RBCs), white blood cells (WBCs) and platelets. The RBCs carry oxygen from the lungs; the WBCs help to fight infection; and platelets are parts of cells that the body uses for clotting. All blood cells are produced in the bone marrow. As children, most of our bones produce blood. As we age this gradually diminishes to just the bones of the spine (vertebrae), br**stbone (sternum), ribs, pelvis and small parts of the upper arm and leg. Bone marrow that actively produces blood cells is called red marrow, and bone marrow that no longer produces blood cells is called yellow marrow. The process by which the body produces blood is called hematopoiesis.

All blood cells (RBCs, WBCs and platelets) come from the same type of cell, called the pluripotential hematopoietic stem cell. This group of cells has the potential to form any of the different types of blood cells and also to reproduce itself. This cell then forms committed stem cells that will form specific types of blood cells.

Lymph is blood plasma that escapes from the blood vessels is absorbed into the surrounding tissue. This tissue fluid collects in tubes throughout the body and is known as lymph. From the lymph tubes, it returns to the blood after passing through a lymph node. If you’ve ever broken a blister, you’ve seen lymph. It’s a colorless, slightly sticky liquid. Lymph is an important part of the circulatory system. It aids the body’s absorption of nutrients and helps to remove waste from the tissue. The lymph collects the body’s waste and then deposits it in a lymph node as it passes through.

Blood tests are used for detecting various disorders, which are dicussed invidually in the following chapters. Here are mentioned the common blood tests performed in routine to detect any disorder or inflammation in the body.

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