Aging
Aging, irreversible biological changes that occur in all living things with the passage of time, eventually resulting in death. Although all organisms age, rates of aging vary considerably. Fruit flies, for example, are born, grow old, and die in 30 or 40 days, while field mice have a life span of about three years. Dolphins may live to age 25, elephants to age 50, and Galápagos tortoises to 100. These life spans pale in comparison to those of some species of giant sequoia trees, which live hundreds of years.
Among humans, the effects of aging vary from one individual to another. The average life expectancy is around 75 years, almost twice what it was in the early 1900s. Although some people never reach this age, and others are beset with illnesses if they do, more and more people are living healthy lives well into their 90s and older. The study of the different aging processes that occur among individuals and the factors that cause these changes is known as gerontology. Geriatrics is a medical specialty concerned with the prevention, diagnosis, and treatment of diseases in the elderly.
Several general changes take place in the human body as it ages: hearing and vision decline, muscle strength lessens, soft tissues such as skin and blood vessels become less flexible, and there is an overall decline in body tone.
Most of the body's organs perform less efficiently with advancing age. For example, the average amount of blood pumped by the heart drops from about 6.9 liters (7.3 quarts) per minute at age 20 to only 3.5 liters (3.7 quarts) pumped per minute at age 85. For this same age range, the average amount of blood flowing through the kidneys drops from approximately 0.6 liters (0.6 quarts) per minute to 0.3 liters (0.3 quarts). Not all people experience decreased organ function to the same degree—some individuals have healthier hearts and kidneys at age 85 than others do at age 50.
The immune system also changes with age. A healthy immune system protects the body against bacteria, viruses, and other harmful agents by producing disease-fighting proteins known as antibodies. A healthy immune system also prevents the growth of abnormal cells, which can become cancerous. With advancing age, the ability of the immune system to carry out these protective functions is diminished—the rate of antibody production may drop by as much as 80 percent between age 20 and age 85. This less-effective immune system explains why a bout of influenza, which may make a young adult sick for a few days, can be fatal for an elderly person. Thus, it is as important for an older person to be vaccinated against the flu and pneumonia as it is for young people to be vaccinated against childhood diseases.
Among humans, the effects of aging vary from one individual to another. The average life expectancy is around 75 years, almost twice what it was in the early 1900s. Although some people never reach this age, and others are beset with illnesses if they do, more and more people are living healthy lives well into their 90s and older. The study of the different aging processes that occur among individuals and the factors that cause these changes is known as gerontology. Geriatrics is a medical specialty concerned with the prevention, diagnosis, and treatment of diseases in the elderly.
Several general changes take place in the human body as it ages: hearing and vision decline, muscle strength lessens, soft tissues such as skin and blood vessels become less flexible, and there is an overall decline in body tone.
Most of the body's organs perform less efficiently with advancing age. For example, the average amount of blood pumped by the heart drops from about 6.9 liters (7.3 quarts) per minute at age 20 to only 3.5 liters (3.7 quarts) pumped per minute at age 85. For this same age range, the average amount of blood flowing through the kidneys drops from approximately 0.6 liters (0.6 quarts) per minute to 0.3 liters (0.3 quarts). Not all people experience decreased organ function to the same degree—some individuals have healthier hearts and kidneys at age 85 than others do at age 50.
The immune system also changes with age. A healthy immune system protects the body against bacteria, viruses, and other harmful agents by producing disease-fighting proteins known as antibodies. A healthy immune system also prevents the growth of abnormal cells, which can become cancerous. With advancing age, the ability of the immune system to carry out these protective functions is diminished—the rate of antibody production may drop by as much as 80 percent between age 20 and age 85. This less-effective immune system explains why a bout of influenza, which may make a young adult sick for a few days, can be fatal for an elderly person. Thus, it is as important for an older person to be vaccinated against the flu and pneumonia as it is for young people to be vaccinated against childhood diseases.
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