CIRCULATION FUNCTION & STRUCTURE


The circulatory system is responsible for the efficient transportation of blood from one part of the body to another. It carries oxygen and nutrients to the cells and transports waste, including carbon dioxide, from the tissues to the organs of elimina tion. Blood also assists in temperature regulation.


The parts of the body that comprise the circulatory system are the heart, arteries, veins and capillaries. The heart is a pump, capable of forcing blood to the lungs and the rest of the body. The heart is divided into the right and left halves and each half has two chambers.


Arteries carry oxygenated blood away from the heart. They have elastic walls and are lined with muscle, permitting the arteries to vary their capacity. Small arteries connect larger arteries to web-like capillaries. The capillaries carry blood from the arteries to the veins. They are very small, thin walled, forming a network where the gas exchange takes place.


Veins carry deoxygenated blood back to the heart. They have thinner walls and are less elastic than the arteries. When blood enters the veins from the capillaries and is under low pressure. To precipitate blood flow back to the heart, the muscles around the veins produce a milking action forcing blood forward. Back flow of blood is prevented primarily by one-way valves located in the veins.


Composition of the Blood


Blood contains both plasma and solids. Plasma is 90% water and the solids are both red and white blood cells.


White blood cells are used to fight off disease and protect the body from infection.


Red blood cells are utilized to transport oxygen to the cells and remove CO2 through the lungs. Red blood cells are manufactured in the bone marrow. Their life cycle lasts about 120 days.


The circulatory and respiratory systems work together to keep the body functioning efficiently in many difficult circumstances. We will now explore how hypoxia affects these systems and how you can recognize and treat the tell tale signs and symptoms.


The Magic of Red Blood Cells


Produced in bone marrow, red blood cells number approximately 35 trillion in the body. Red blood cells are largely made up of a substance called hemoglobin. Each RBC contains approximately 250 million hemoglobin molecules. These hemoglobin molecules carry 4 molecules of oxygen each, meaning each red blood cell can carry approximately 1 billion oxygen molecules. The secret of hemoglobin is that it contains one atom of iron for every hemoglobin molecule. This gives the blood a chemical attraction for oxygen as well as its red color. The red blood cells carry 95% of all oxygen, while the remainder is suspended in plasma. It can be easily noticed in a person who is anemic. Their lack of adequate, functioning red blood cells will cause them to begin to suffer the effects of a lack of oxygen at a relatively low altitude.


High Altitude Awareness Training 12


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