THE AGING PROCESS
All vital organs begin to lose some function as you age. Aging changes have been found in all of the body's cells, tissues and organs, and these changes affect the functioning of all body systems. Living tissue is made up of cells. There are many different types of cells, but all have the same basic structure. Tissues are layers of similar cells that perform a specific function. The various kinds of tissues group together to form organs.
There are four basic types of tissue:
- Connective tissue supports other tissues and binds them together. This includes bone, blood, and lymph tissues in addition to the tissues that give support and structure to the skin and internal organs.
- Epithelial tissue provides a covering. The skin and the linings of the various passages inside the body are made of epithelial tissue.
- Muscle tissue includes two types of tissue:
- Striated muscles, such as those that that move the skeleton (also called voluntary muscle)
- Smooth muscles, such as the muscles that surround the stomach
- Nerve tissue is made up of nerve cells (neurons) and is used to carry messages to and from various parts of the body. The brain is made of nerve tissue.
AGING CHANGES
Cells are the basic building blocks of tissues. All cells experience changes with aging. They become larger and are less able to divide and reproduce. Among other changes, there is an increase in pigments and fatty substances inside the cell (lipids). Many cells lose their ability to function, or they begin to function abnormally.
Waste products accumulate in tissue with aging. A fatty brown pigment called lipofuscin collects in many tissues, as do other fatty substances.
Connective tissue changes, becoming increasingly stiff. This makes the organs, blood vessels, and airways more rigid. Cell membranes change, so many tissues have more trouble receiving oxygen and nutrients and getting rid of carbon dioxide and wastes. Many tissues lose mass. This process is called atrophy. Some tissues become lumpy (nodular) or more rigid.
Because of cell and tissue changes, your organs also change as you age. Aging organs gradually but progressively lose function, and there is a decrease in the maximum functioning capacity. Most people do not notice this loss, because you seldom need to use your organs to their fullest capability.
Organs have a reserve ability to function beyond the usual needs. For example, the heart of a 20-year-old is capable of pumping about 10 times the amount that is actually needed to preserve life. After age 30, an average of 1% of this reserve is lost each year.