The pumping action of the heart keeps your blood in constant motion, sending it coursing through your vascular system through intricate tube-like structures called blood vessels. As your blood travels through the body, it drops off life-sustaining oxygen and nutrients, which are picked up by the cells and converted into energy.
Red Blood Cells
In a healthy individual, a single drop of blood contains as many as 50 million red blood cells, also called erythrocytes, which are microscopic biconcave disks. Erythrocytes are manufactured in your bone marrow and live approximately 120 days. These cells break down and are gobbled up and digested by macrophages, or white blood cells.
Hemoglobin
Erythrocytes are filled with about 300 million molecules of a substance called hemoglobin. Chemically speaking, hemoglobin and oxygen have an affinity for each other, allowing them to seamlessly link together. In the lungs, where the environment is rich with oxygen, this affinity allows oxygen to easily attach to the hemoglobin to form oxyhemoglobin. This substance stays close to the surface of the red blood cell, facilitating an easy transfer to the cells.
Oxygen Uptake
As your blood travels into the tiny capillaries throughout your body, the close proximity of the erythrocytes to other cells allows your cells to attract, absorb and use this freely available oxygen for energy production. This process occurs easily because the association between oxygen and hemoglobin is similar to a very weak magnet, allowing the hemoglobin to easily release the oxygen molecules as they come in contact with other cells.
Nutrients
Your blood provides a constant supply of fresh oxygen and nutrients in the forms of amino acids, glucose and cholesterol, as well as numerous other substances. Your body handles these nutrients differently than oxygen. Nutrients are broken down into microscopic molecules by digestive enzymes. These nutrients are released from your digestive system and picked up in the bloodstream and ultimately deposited throughout your body. However, it's not quite that simple. Certain vitamins and minerals work synergistically to allow absorption. When your body is out of balance, certain nutrients are not effectively absorbed and transported, which is why eating a balanced diet is so important.
Waste
In addition to providing the transport medium for nutrients, your blood also picks up waste in the form of carbon dioxide, which moves out of the tissues into the blood and is taken to the heart and then to the lungs, where it is dropped off and exhaled. Other wastes are filtered from your blood and excreted into your urine by the kidneys, through which all the blood in the circulatory system passes many times a day.
