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 tissue group together to form organs. 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.
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.