SECTION 1: FLOW

The human body depends on the constant flow of air and blood to carry the nutrients vital to survival. Air flows into the body whereupon oxygen is removed and transferred into the blood. Oxygen and other nutrients flow through the body to a purposeful destination. The byproducts of metabolism such as carbon dioxide and waste then travel to their destination for removal. The lungs, heart, blood and its vessels, and the spleen are the organs facilitating the intake, storage, and transportation of the products. All processes require a constant movement or flow through the body to effectively reach every cell of the body.

The upper airway parts include the nasal and oral cavity, the larynx (voice box), and pharynx (throat).  The lungs, trachea (windpipe), and bronchi (air passageways) make up the lower part of the respiratory system. The upper respiratory system is responsible for the warming and filtering of inspired air. The lower respiratory system is responsible for removal of oxygen from inspired air and transferring it to cells in the blood stream. At the same time, carbon dioxide (the byproduct of cellular metabolism) is removed from the blood stream and expelled from the body through exhalation. The function of breathing is controlled by the brain through signals resulting from high levels of carbon dioxide or low levels of oxygen in the blood.

It is difficult to determine if age changes to the respiratory system are related to long-term exposure to pollutants or to structural changes over time due to the effects of use or gravity. One example of exposure to pollutants is the carbon buildup found in the lungs of older non-smokers. An example of structural change is the effect of Kyphosis (increased spinal curve in the thoracic area) on one's ability to inflate the lungs adequately. In this situation the chest cavity is distorted and more rigid, resulting in impaired ability to breathe deeply.

Lung tissue becomes more rigid with aging resulting in decreased vital capacity, the total amount of air that can be moved into and out of the lungs. There is also more residual volume, the amount of air that stays in the lungs after exhalation. The muscles used to move the chest wall for breathing become weaker and therefore less effective. The resulting decreased pulmonary efficiency effects elders in the following ways:

1. Ability to tolerate heavy exertion for long periods, needing frequent rest periods, is decreased.

2. Oxygen supply to other tissues of the body, especially during physical exertion, is decreased.

3. Risk of respiratory infection when sedentary related to a less effective cough response is increased.

The heart is a muscle that functions as a pump. The pumping action of the heart rhythmically moves blood throughout a network of blood vessels (arteries, veins, and capillaries). This cardiovascular system is responsible for transporting nutrients to each cell and waste products away from the cells for removal from the body.

The heart becomes weaker with age, as with most muscles, and therefore has reduced pumping efficiency. In normal circumstances this reduced cardiac output is adequate for an older adult to function normally because of reduced body demands. When greater demand is made on the heart muscle from the stress of illness or exertion, most elders are able to compensate with greater energy exertion and longer recovery time.

There are three major types of blood vessels. Arteries carry oxygenated blood, veins carry deoxygenated blood, and the capillaries are the tiny connecting vessels between the arteries and veins. Blood vessels become less elastic with age affecting the blood flow to various organs such as the heart, kidneys, and liver. In our culture there is a diet related build up of cholesterol lining the walls of the arteries which limits or obstructs blood flow. In some cases the result may be elevated blood pressure. In other cases the function of particular organ may be affected by the impaired circulation. In extreme cases this condition can lead to heart attack or stroke. Physical conditioning and diet can modify some of the effects of aging to the cardiovascular system.

Blood consists of formed elements transported in a fluid called plasma. Some of the formed elements include red blood cells, white blood cells, and platelets. Many other elements are found in the fluid, including vitamins, minerals, cholesterol, and the various byproducts of metabolism. The function of blood is to regulate pH, body temperature and body fluids; and protect against foreign materials harmful to the body. Usually, any changes to the blood are related to disease rather than to aging.

The lymphatic system consists of a network of channels, lymph nodes, spleen, and thymus. The channels drain fluid from interstitial spaces (found between cells) that has leaked from capillaries. This lymphatic fluid travels through lymph nodes where bacteria and other foreign agents are filtered out and destroyed by the immune system. The thymus and spleen are responsible for producing the specialized cells for the immune system. The lymphatic fluid eventually makes its way back into the blood system.

The thymus organ is the only part of the lymphatic system that undergoes age related changes. The thymus is largest at or about two years of age; it begins to undergo cell replacement by fatty tissue at sexual maturity; by age twenty it starts a decline in the production of thymosin, the essential hormone involved in regulating immune cell production. Thymosin production almost ceases by age sixty. The only suggested result of the demise of the thymus organ is possibly the slowed responsiveness of the immune system with aging.

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SECTION 2: MOVEMENT

The human body depends on its skeleton to give it form, joints to allow for various positions, and muscles to facilitate action.

Along with ligaments, tendons, and cartilage to hold the various pieces together, the musculoskeletal system allows the body maintain its shape, change postures, and move through the environment.

Muscles are made up of cells that have the unique ability to contract and expand. The result of the action of a group of these cells is movement. Muscle function allows for movement of the various parts of the body, changes in the diameter of tubes (blood vessels and large airways of the lung), propulsion of materials through the body, and expulsion of wastes products from the body. Contraction of a muscle produces heat which is transported to other parts of the body by the blood. This action is necessary for maintaining body temperature.

There are three types of muscles in the human body. Skeletal muscle is the type that is attached to the bones of the skeleton by tendons providing for movement. Smooth muscle is found in the walls of hollow organs and tubes, such as the stomach and blood vessels. Cardiac muscle forms the walls of the heart. Muscle activation is controlled by the nervous system, hormones, and some factors within the muscles themselves. Activation of some muscles are voluntary (skeletal) and others involuntary (heart muscle).

Bones and muscles become weakened from lack of use. Muscles will atrophy causing as then to be smaller and weaker. Exercise stretches muscles placing tension on bones. It is this tension that allows bones to remain strong. Lack of exercise or stress on bones causes bones to loose their minerals and therefore become brittle and easily broken.

The skeleton serves several functions. First, its composition of bones and ligaments (connective tissue that hold bones together) provide structure for an otherwise fleshy mass. Specific bones connected in a special way that allows for particular directional movements are called joints. The framework of bones allows for the support of weight with upright posture.

Another function of the skeleton is that of protection from injury. The skull encloses the brain, the spinal column protects the spinal cord, and the rib cage surrounds the vital organs in the chest cavity.

Bones also serve as a reservoir, storing fat and specific minerals such as calcium, phosphorus, sodium and potassium. The manufacture of blood cells occurs in the marrow of specific bones.

The effects of age on the musculoskeletal system are related to the slower pace and reduced amount of activity usually seen with increasing age. Factors other than sedentary lifestyle, such as nutritional deficiency and chronic illness, interfere with attributing the exact cause of muscle weakness solely on aging. In any case, the result is that muscles tend to loose bulk and strength, most likely from the loss of muscle cells over time. The exciting news generated from recent research is that it is never too late to build muscle tone and strength through high intensity resistance exercise training. One study reported in The New England Journal of Medicine demonstrated that weight training of the lower body by a group of frail elders of average age 87 resulted in increased strength and mobility (Fiatarone et al., 1994).

The effect of age on joints can be attributed to the stress of use over time, especially improper use and lack of exercise. Heavily used joints such as knees and ankles can become less flexible due to cartilage and ligament calcification. The bones in the hands, knees and feet may suffer erosion type damage due to overuse. The use of damaged joints, already limited by decreased flexibility, results in pain and reduced range of motion. The outcome from experiencing stiff and painful joints is a continual decline in the types of movement that cause pain, leading to even more stiffness. When stiffness of joints limits their use, muscles and bones are not stressed enough to maintain proper function. Muscles become weaker and bones become brittle. Loss of flexibility from weakened muscles and degenerated joints can usually be reversed with appropriate exercise.

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