Most people have some knowledge of the blood circulating system in the body and how it works. Blood is pumped away from the heart, through the arteries, arterioles, and capillaries, and returns to the heart through the venules and the veins. However, there is another “vascular system” in the body that most people do not know about. It is called the lymphatic system.
The lymphatic system is a network of fluid carrying vessels, much like the cardiovascular system, whose vessels are structured much like veins. However, the lymphatic vessels are not filled with blood. As blood circulates through the body some of its fluid content (about 10% of the total blood volume per one complete circuit through the body), containing cell waste and proteins, leaks out of the blood vessels and infiltrates the body tissues. Left unchecked, this phenomenon would ultimately cause a build up of fluid and waste products in the body, resulting in toxicity, swelling and weight gain from the increased body water content. The job of the lymphatic system is to pick up the fluid lost from the blood and return it to the heart, thus preventing build up of toxic substances and excess fluid in the body. Once the fluid enters the lymphatic vessels, through one way valves, it is called lymphatic fluid or just lymph. The ultimate example of what can happen in response to a deficit in lymphatic function is demonstrated by the disease called elephantiasis. In this disease, the lymphatic vessels become blocked, the flow of lymph fluid is impaired, fluid and toxic waste builds up in the body tissues, and swelling ensues until the point of damage to or the death of the affected tissue.
A unique characteristic of the lymphatic system is that there is no pump, like the heart, associated with its vascular network. There is no active, continuous, mechanism in the body which puts pressure on the fluid in the lymphatic vessels in order to drive it back toward the heart. There are however other types of methods that the body uses to push the lymph in the direction of the heart and thus put it back into the blood circulatory system. One method that the body uses involves respiration, breathing. When an individual inhales, the thoracic cavity expands and a negative pressure is developed within the cavity. This negative pressure essentially sucks the lymphatic fluid toward the thoracic cavity and thus toward the heart. The faster and deeper one breathes the larger the negative pressure generated in the thorax and the faster the lymph fluid flows back toward the heart. A second method that the body uses to get lymph fluid back to the heart is called the muscular pump. When skeletal muscles contract they squeeze the lymphatic vessels present within themselves, and in other parts of the body, and ultimately propel the lymph fluid back toward the heart. The flow of lymph fluid is one-way only, from the peripheral tissues toward the heart, because the lymphatic vessels have one-way valves in them which prevent backflow, away from the heart, once the lymph fluid has moved forward. So, with every deep breadth and every contraction of the skeletal muscles of the body, lymph fluid is propelled toward the heart.
Here is where exercise comes into the scheme. Exercise causes increases in the rate and depth of breathing, and it causes the skeletal muscles to contract heavily. Both of these functions then cause the lymph fluid to move toward the heart. When the lymph fluid is continually being pumped back into the blood, the blood volume then is constantly being replenished and the cellular waste products in the lymph fluid can enter the blood and be removed by the kidneys and liver. This then alters the compartmentalization of the fluid in the body. The blood volume remains within normal limits, while the fluid and cell waste which might have accumulated in your body tissues through lack of exercise, is decreased. This causes a natural decrease in body weight through decreasing body water content and a natural detoxification of your body by getting waste products out of the body tissues and into the blood where they can ultimately be removed by the kidney and liver.
Dr. J
Dr. J’s Personal Training
Newtown Square Shopping Center
Newtown Square, Pa 19073
References:
Medical Physiology
Eleventh edition
Guyton and Hall
Elsevier Inc.
1600 John F. Kennedy Boulevard, Suite 1800
Philadelphia, Pa 19103-2899
Human Anatomy and Physiology
Fourth Edition
Marieb E. N.
Benjamin Cummings Sciences Publishing
2725 Sand Hill Road
Menlo Park, California 94025
The Human Body in Health and Illness
Second Edition
Herlithy, Maebius
Saunders
11830 Westline Industrial Drive
Saint Louis, Missouri 63146
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