Expected Age-Related Changes

With aging, the epidermis becomes more fragile, increasing the risk for skin damage such as tears, maceration, and infection. Rashes caused by contact with chemicals, such as detergents or cosmetics, are increasingly common in older individuals. Skin repairs more slowly in older than in younger individuals, increasing the risk for infection.

The walls of the capillaries become increasingly fragile with age and may hemorrhage, leading to senile purpura, the red, purple, or brown areas commonly seen on the legs and arms. By 70 years of age, the body has approximately 30% fewer cells than at age 40. The remaining cells enlarge, so body mass appears approximately the same. Total body fluid decreases with age. Plasma and extracellular volume remain somewhat constant, but intracellular fluid decreases. This loss of intracellular fluid increases the risk for dehydration. Tissue changes include a decrease in subcutaneous tissue that is visible in the eye orbits, hollows in the supraclavicular space, and sagging of breasts and neck tissue.

Common Disorders Seen with Aging

Bones

Bone consists of protein and the minerals calcium and phosphorus. Calcium is necessary for bone strength, muscle contraction, myocardial contraction, blood clotting, and neuronal activity. It is normally obtained by eating dairy products and dark-green leafy vegetables. Vitamin D is needed for the absorption of calcium and phosphate through the small intestine; vitamins A and C are needed for ossification, or bone matrix formation.

For the long bones to remain strong, adequate dietary intake of these nutrients is important. However, the dietary intake of minerals alone does not maintain bone strength. It is also necessary to apply stress to the long bones to keep the minerals in the bones. This needed stress is best provided by weight-bearing activities such as standing and walking. The calcium that is needed for clotting and nerve and muscle functions is constantly being withdrawn from the bone and moved into the bloodstream to maintain consistent blood levels. Calcium is normally redeposited in the bone at an equal rate, replacing the calcium that is lost. As long as this movement of calcium is in balance, the bone remains strong.

Hormones also play an important role in bone maintenance. Calcitonin, which is produced by the thyroid gland, slows the movement of calcium from the bones to the blood and lowers the blood calcium level. Parathyroid hormone (PTH) increases the movement of calcium from the bones to the blood and increases the blood calcium level. PTH also increases the absorption of calcium from the small intestine and kidneys, thus further increasing the blood calcium level. Insulin and thyroxine aid in the protein synthesis and energy production needed for bone maintenance. Estrogen and testosterone, produced by the ovaries and testes, respectively, help retain calcium in the bone matrix.

Vertebrae

The spinal column consists of a series of small bones, called vertebrae, that stack up to form a strong, flexible structure. The spinal column supports the head and allows for flexible movement of the back. The segments of the spinal column consist of cervical, thoracic, lumbar, and sacral vertebrae. The muscles that move the back connect at bony processes that protrude from each vertebra. The spinal cord, the nerve tissue that extends downward from the brain, passes through the vertebral canal, which runs through an opening in each vertebra. The bones of the spinal column protect this nerve tissue from injury.

Fibrous pads, called intervertebral disks, are located between the vertebrae and cushion the impact of walking and other activities.

Joints

Tendons and Ligaments

Tendons are structures that connect the muscles to the bone, and ligaments are structures that connect bones to other bones.

Muscles

There are three types of muscle tissue in the body: cardiac muscle, smooth muscle, and skeletal muscle. Cardiac muscle, located in the heart only, is responsible for the pumping action of the heart that maintains the blood circulation. Smooth muscle is found in the walls of hollow organs such as the blood vessels, stomach, intestines, and urinary bladder. Because cardiac and smooth muscle normally cannot be stimulated by conscious effort, they are called involuntary muscles.

Skeletal muscle accounts for the largest amount of muscle tissue in the body. The major function of skeletal muscle is to move the bones of the skeleton. Because their actions can be controlled by conscious effort, skeletal muscles are considered voluntary muscles. Muscles are connected to bones by tendons. Contraction or relaxation of muscles causes the bones to move. Controlled and coordinated movement of bones and muscles allows us to perform the variety of movements required for activities of daily living. Special effort and practice allow us to perform special activities such as dancing, playing sports, and playing the piano.

The amount of muscle mass and the type of muscle development differ greatly among individuals. Men normally have larger muscles, or more muscle mass, than do women, particularly in the muscles of the upper body. The male hormone testosterone stimulates muscle development. In both men and women, the largest and strongest skeletal muscles are found in the legs and upper arms; the smallest and weakest are located in the lower back.

Muscle tissue is normally in a state of slight contraction. This muscle tone is necessary to support the head, to keep the spine erect, and to perform any controlled movement. Muscle mass is built and muscle tone is maintained by means of exercise. There are two general types of exercise: isometric exercise, which involves muscle contraction without body movement, and isotonic exercise, which involves muscle contraction with body movement. Isometric exercise helps maintain muscle tone and strength but does little to increase muscle size. Isotonic exercise maintains muscle tone and strength and increases muscle mass if it is done repetitively. Aerobic exercise is isotonic exercise that occurs for 30 minutes or longer. Aerobic exercise strengthens the skeletal, cardiac, and respiratory muscles. People who lead inactive or sedentary lifestyles suffer from the lack of isotonic exercise. Regardless of age, unless people undertake an exercise program, they manifest poor muscle development and strength.

Muscle movement is controlled by impulses from the parietal lobes of the cerebrum and is coordinated by impulses from the cerebellum. Muscle sense is a term used to describe the brain’s ability to recognize the position and action of the muscles without conscious effort. Receptor cells in the muscles, called proprioceptors, send information to the brain that enables it to integrate all body movements. This coordinative function of the brain allows us to walk, bend, or eat without consciously thinking about all of the separate movements and feeling all of the different positions.

Muscles need energy to function. The most abundant source of muscular energy is glycogen. Adenosine triphosphate (ATP), the direct energy source for muscular contraction, is a product of glycogen metabolism. Glycogen is first broken down into glucose. During cell metabolism, glucose interacts with oxygen transported in the bloodstream by hemoglobin or oxygen stored in the muscle fibers as myoglobin. This reaction involves the production of ATP, heat, water, and carbon dioxide. If muscle fibers do not receive enough oxygen, glucose may not be oxidized completely, and a chemical intermediate, lactic acid, is produced. Elevated levels of lactic acid may result in muscle fatigue and soreness.

Expected Age-Related Changes

The intervertebral disks shrink as the thoracic vertebrae slowly change with aging. This results in a condition called kyphosis, which gives the older adult a stooped or hunchback appearance, with the head dropping forward toward the chest. The combination of disk shrinkage and kyphosis results in loss of overall height. A person can lose as much as 2 inches of height by age 70. People who are concerned about their appearance find these changes disturbing because clothing no longer fits properly, and it is increasingly difficult to find flattering styles.

Connective tissues tend to lose elasticity, leading to restriction of joint mobility. Loss of flexibility and joint mobility begins as early as the teen years and is common with aging. Regular stretching exercises can help slow or even reverse flexibility problems.

Muscle tone and mass typically decrease with aging, and these decreases are directly related to decreased physical activity and exercise. People of all ages who exercise regularly have better muscle mass and tone. Hormonal changes, particularly the decrease in testosterone level, tend to reduce muscle mass in aging men. Reduction in blood supply to the muscles as a result of aging or disease can lead to changes in muscle function. Less glycogen is stored in aging muscles, thereby decreasing the fuel available for muscle contraction. Any condition that restricts oxygen availability (e.g., anemia and respiratory problems) can lead to an excessive production of waste products such as lactic acid and carbon dioxide. This can increase the incidence of muscle spasms and muscle fatigue with minimal exertion. Decreased endurance and agility may result from a combination of these factors. Neuronal changes in the areas of the brain responsible for muscle control can result in alterations of muscle sense, which may be observed in older adults as an unsteady gait and impairment of other activities that require muscular coordination.

As a person ages, muscle mass decreases, and the proportion of body weight resulting from fatty, or adipose, tissue increases. This is significant in the administration of medications. Intramuscular injection sites may not be as well muscled, and fatty tissue tends to retain medication differently than does lean tissue. Absorption and metabolism of drugs can be significantly different from those in younger persons.

Common Disorders Seen with Aging

Upper Respiratory Tract

On its way to the lungs, air passes through the upper respiratory tract, which includes the air passages of the nose, mouth, and throat, all of which are located above the chest cavity. Mucous membranes line the nasal passages and warm and humidify the air that passes through the nose. Cilia and mucus in the nasal passages trap particulate matter (bacteria and debris) and sweep it toward the pharynx, where it is routinely swallowed and destroyed by gastric acid. The cough and sneeze reflexes also help prevent debris and foreign objects from entering the respiratory tract. The pharynx, which is located at the back of the oral cavity, has three segments: the oropharynx, nasopharynx, and laryngopharynx.

The nasopharynx is connected to the middle ear by the eustachian tubes, which help maintain proper air pressure in the middle ear. The larynx, or voice box, is composed of cartilage rings and folds of tissue, called vocal folds. The epiglottis, which is the uppermost cartilage ring, prevents food from entering the airway. During inhalation, the vocal folds move to the sides of the larynx to allow air to pass freely. During exhalation, we can speak and sing by controlling the distance between these folds, which vibrate when air is forced through them and produce sound.

Lower Respiratory Tract

The lower respiratory tract includes the lower trachea, bronchial passages, and alveoli, all of which lie within the chest cavity. The trachea is a cartilaginous passageway that connects the larynx to the bronchial passages of the lungs. The trachea branches into two major bronchi, which further divide like the branches of a tree into smaller and smaller bronchioles. At the ends of the bronchioles are the alveoli, or air sacs, which are the functional units of respiration. A thin layer of fluid lines each tiny air sac, which is surrounded by pulmonary capillaries to allow the efficient exchange of gases by diffusion. It is here that oxygen enters the bloodstream for transport to body tissue, and it is here that carbon dioxide from the body leaves the bloodstream. This gaseous exchange is essential for normal cell function and for the maintenance of the blood’s acid-base balance.

Because the alveoli have a moist lining, their surfaces could adhere if they touched when the alveoli were empty. This is prevented by a special protein substance called surfactant.

Air Exchange (Respiration)

The movement of air into and out of the alveoli is called ventilation. Ventilation requires the action of muscles, primarily the diaphragm and the intercostal muscles. During inhalation, the diaphragm contracts and moves downward while the intercostal muscles pull the ribs upward and outward. These combined activities increase the size of the chest cavity until the air pressure inside the lungs is lower than the atmospheric pressure and air is drawn into the lungs. This process is known as inhalation or inspiration. When the air pressure inside the lungs equals or exceeds atmospheric pressure, air ceases to enter the lungs. When the diaphragm and intercostal muscles relax, the diaphragm moves upward and the ribs move inward, making the chest cavity smaller. As the chest cavity becomes smaller, the pressure in the lungs becomes greater than the atmospheric pressure. Air is forced out of the lungs until the pressure in the lungs equals the atmospheric pressure. This action is known as exhalation or expiration. Regulation of respiration is both neurologic and chemical. The respiratory centers in the medulla and pons of the brainstem continuously monitor and control the rate and depth of involuntary respiration. Most breathing is unconscious and involuntary. If we had to think about inhaling and exhaling every breath, we would have little time to do anything else. However, breathing can be conscious and voluntary. When swimming, singing, or engaging in other activities that require breath control, we can temporarily alter our breathing patterns.

Expected Age-Related Changes

Musculoskeletal system changes that occur with aging alter the size and shape of the chest cavity. Kyphosis contributes to a barrel-chested appearance. Costal cartilage located at the ends of the ribs calcifies and becomes more rigid, thus reducing the mobility of the rib cage. Intercostal muscles atrophy, and the diaphragm flattens and becomes less elastic. All of these changes reduce lung capacity and interfere with respiratory function, resulting in a decreased ability to inhale and exhale deeply.

Several factors increase the possibility of inadequate oxygenation and the risk for respiratory tract infections in older adults. The cilia movement inside the lungs decreases. The airways and alveoli are less elastic, and there is a decrease in the number of capillaries surrounding the alveoli, which interferes with gas exchange. The lung tissue itself has decreased physical mobility and elasticity, with can lead to increased pooling of secretions, especially in the lower lobes.

Common Disorders Seen with Aging

Heart

The heart is a muscular organ located centrally in the thoracic cavity between the lungs. The sternum, or breastbone, protects its anterior surface. The heart’s tip, or apex, projects toward the left side of the body and extends directly above the diaphragm muscle.

Three pericardial membranes form a sac around the heart. The innermost membrane is on the surface of the heart and is called the epicardium, or visceral pericardium. The middle membrane is the parietal pericardium, and the outermost membrane is the fibrous pericardium. The space between the epicardium and the parietal pericardium is the pericardial cavity; it contains a small amount of serous fluid that prevents the membrane surfaces from rubbing together during cardiac activity.

The heart, which is composed of cardiac muscle (called myocardium), is a hollow organ with four distinct chambers. The right side of the heart consists of the right atrium and right ventricle, which are separated by the tricuspid valve. The right side of the heart is a low-pressure pump that moves deoxygenated blood through the pulmonary valve and pulmonary artery and out to the lungs. After the blood is oxygenated, it returns to the left side of the heart through the pulmonary vein. Because less effort is required to move blood the short distance through the lungs of a healthy individual, the muscle wall of the right side of the heart is relatively thin. The left side of the heart also has two chambers, the left atrium and left ventricle, which are separated by the mitral valve. The pressure within the left side of the heart is higher than that in the right side because the left side is responsible for blood distribution to the entire body. To provide the necessary force, the left ventricle has a thicker muscle wall than does the right ventricle. When blood leaves the left ventricle, it proceeds through the aortic valve into the aorta and its branches and out to the rest of the body.

The heart chambers and valves are lined with endocardial tissue. Endothelial tissue continues out from the heart and lines all of the blood vessels. This smooth layer allows the blood to flow freely and reduces the risk for clot formation.

Blood Vessels

The arteries are blood vessels that carry blood away from the heart. With the exception of the pulmonary artery, arteries carry oxygenated blood. The aorta, the largest artery in the body, leaves the heart and branches into a series of progressively smaller arteries and capillaries. These vessels run through the entire body and reach all organs and tissues.

Arterial walls are composed of three layers of tissue. The innermost layer is the endothelium, or tunica intima. This layer is a continuation of the endocardial tissue that lines the inside of the heart. The middle layer, or tunica media, is composed of smooth muscle and connective tissue. This smooth muscle is controlled by the autonomic nervous system and dilates or constricts the artery to maintain the blood pressure. The outermost layer, or tunica externa, is composed of strong fibrous tissue that protects the vessels from bursting or rupturing under high pressure. The relative thickness of the tunica media and externa enables the arteries to perform properly.

The veins are vessels that carry blood toward the heart. With the exception of the pulmonary vein, veins carry deoxygenated blood. Venules, the smallest veins, are connected to the smallest capillaries. Veins and venules are composed of the same three layers of tissue seen in arteries. The veins use a system of valves, which are created by endothelial tissue folds, to aid in the return of blood to the heart. The valves prevent backflow of blood, which could be a problem when the blood is moving toward the heart against the force of gravity.

The smooth muscle layer of the veins is much thinner than that of the arteries because the veins are not as important in the regulation of blood pressure. The outer fibrous layer is also thinner because blood pressure in the veins is much lower than that in the arteries.

A special set of blood vessels, the coronary arteries and veins, supplies the heart with blood enriched with oxygen and nutrients. These arteries are the first branches of the ascending aorta. Because the heart muscle works continuously, it has high oxygen demands. Any condition that obstructs the normal supply of blood to the heart can damage the myocardium. If it is severely deprived of oxygen and nutrients, the heart muscle will die. Too much damaged or destroyed tissue results in cardiovascular system failure and death.

Conduction System

To function effectively, the cardiovascular system must work in a controlled, organized, and rhythmic manner. The heart’s rhythm is established by specialized cells within the heart muscle that make up the electrical system of the heart. The body’s natural pacemaker, the sinoatrial node, is a group of specialized cells in the right atrium. Impulses generated in the sinoatrial node travel across the atria to the atrioventricular node in the lower interatrial septum. From there they are conducted through the bundle of His, through the right and left bundle branches, through the Purkinje fibers, and, finally, to the ventricular myocardium. When the cells of the heart’s electrical system depolarize, the myocardium depolarizes and the heart contracts (systole), following which the special cells and the myocardium repolarize as the heart relaxes (diastole). This process alternately empties and fills the chambers, which pump blood through the circulatory system.

The heart valves show some degree of thickening and increased calcification with aging, resulting in mild degrees of mitral valve regurgitation. As in other body tissues, the endocardium and endothelium lose elasticity with aging. When these tissues become increasingly fibrous and sclerotic, venous return from the peripheral areas of the body decreases. Orthostatic hypotension occurs because the circulation does not respond quickly to postural changes. Less effective pumping of the heart muscle combined with sclerotic changes in the veins can lead to dependent edema and to the appearance of varicosities in the lower extremities. Weakness of the valves in the rectal veins can lead to hemorrhoids.

Common Disorders Seen with Aging

Cardiovascular disease is the leading cause of morbidity and mortality in the United States, accounting for more than 75% of all deaths in men and women older than 65 years of age.