Effects of Aging on Various Tissues

Effects of Aging on Various Tissues

Early in embryonic development, the three primary germ layers form. They lie on top of each other and are known as the ectoderm, mesoderm, and endoderm. Later, they specialize, forming the four primary tissues making up all body organs. These are the epithelial, nervous, muscle, and connective tissues. After 2 months of development, the primary tissues are present, as are all major organs. Most tissue cells remain mitotic, producing quick growth during gestation. Nerve cells stop dividing or nearly stop dividing while the baby is still a fetus. After birth, most tissue cells continue to divide until the child becomes an adult. At this point, cellular division slows significantly. Some tissues are still able to partially regenerate even after this occurs.

Adult epithelia and blood-forming tissues remain highly mitotic. Certain tissues that regener-ate through life, such as those of the liver, accomplish this by division of mature or specialized cells. In the epidermis and lining of the intestines, abun-dant stem cells are able to divide as needed, producing new cells. Human tissues usually function quite well up through middle age, as long as nutrition and circulation are adequate, and there have been relatively few infections or wounds.

As body tissues age, they are repaired more slowly and much less effectively. Hormone secre-tion slows down and, in general, physical activity becomes less regular. Connective tissues become more fragile, epithelial tissues thin, bones become brittle, and skin bruising occurs more easily. These degenerative processes occur more quickly when an individual is not physically active or consumes a poor diet. Cancer risks increase when an individual has had DNA mutations in highly mitotic cells. Con-tinual damage to the body can lead to cardiovascular disease, deterioration of mental function, and other major health problems. The effects of aging may be genetic, as in the condition known as osteoporosis, which is also related to reductions in sex hormones, lack of exercise, and low dietary calcium. However, healthy bones can be maintained by correcting these deficiencies, and other types of tissue degeneration can be temporarily slowed or even reversed with sup-plements, hormone (and other) therapies, and regular exercise.

1. List the steps of tissue repair.

2. Explain the reason behind the name of “granulation tissue.”