Epithelial tissue provides a covering. It includes the skin, and the linings of the various passages inside the body. It also includes smooth muscle, such as the muscles that surround the stomach. All cells will experience changes with aging. The cells become larger, and are less able to divide and reproduce.
Many cells lose their ability to function, or begin to function abnormally.
General tissue aging changes include an accumulation of waste products in the tissue. A fatty brown pigment called lipofuscin collects in many tissues, as do other fatty substances. The 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 getting needed oxygen and nutrients, and getting rid of carbon dioxide and wastes.