The Aging process
Changes in organs, tissues and cells aging.
All vital organs begin to lose some function as we age. The aging changes have been found in all cells, tissues and organs of the body affecting the functioning of all body systems.
Living tissue is made up of cells, and although there are many different types of them, they all have the same basic structure. Tissues are layers of similar cells that perform a specific function. Different types of tissues group together to form organs.
There are four basic types of tissue:
- Connective tissue.- supports and put together other tissues. This includes bone, blood and lymphatic tissues, and tissues that give support and structure to the skin and internal organs.
- Epithelial tissue.- provides covering for the deeper layers of the body. The skin and the linings of the ducts inside the body are made of epithelial tissue.
- The muscle tissue.- includes three types:
- Striated muscles, such as those that move the skeleton (also called voluntary muscles).
- Smooth muscles (also called involuntary muscles) as stomach contents and other internal organs.
- Infarction, which forms the bulk of the heart wall (also an involuntary muscle).
- The nervous tissue.- consists of nerve cells (neurons) and is used to carry "messages" to and from different parts of the body. The brain, spinal cord and peripheral nerves are composed of nerve tissue.
AGING CHANGES
Cells are the fundamental building blocks of tissues. All cells experience changes with aging, become larger and gradually lose the ability to divide and multiply. Other changes are the increase in pigments and fatty substances inside the cell (lipids) and many cells lose their functional capacity or begin to function abnormally.
The waste products accumulate in the tissue with age. In many tissues, a brown fatty pigment called lipofuscin is accumulated.
Connective tissue changes, becoming more inflexible, making organs, blood vessels and airways stiffer. Cell membranes change, which is why many tissues have more trouble getting oxygen and nutrients, and removing carbon dioxide and waste.
Many tissues lose mass, a process called atrophy. Some tissues become lumpy (nodular) or more rigid.
The organs also change as you age due to changes in cells and tissues. Aging bodies lose functions slowly. Most people do not notice this loss, because one rarely needs to use the organs to their fullest capacity.
Organs have a reserve capacity to operate beyond the common needs. For example, the heart of a person of 20 years is capable of pumping about 10 times the amount you really need to keep the body alive. After age 30, you lose on average 1% of this reserve each year.
The most significant changes in organ reserve occur in the heart, lungs and kidneys. The amount of reserve lost varies between people, and between different organs of the same person.
These changes appear slowly and over a period of time. When an organ is subject to more hard work than usual, it may be unable to increase its role, a situation that can lead to sudden heart failure or other problems.
Factors that produce extra work (body stressors) include the following:
- Diseases.
- Drugs.
- Significant life changes.
- Suddenly increased physical demands on the body, for example:
- A sudden change in activity.
- Exposure to a higher altitude.
Loss of reserve also makes it difficult to restore the balance (equilibrium) of the body. The drugs leave the body at a slower speed. It may require lower doses of medications and side effects become more common.
Side effects of medications may resemble symptoms of many diseases, so it is easy to confuse a reaction to a medication with disease. Some drugs have very different side effects in elderly than younger people.
THEORY OF AGING
No one really knows how and why people change as they age. Some theories claim that aging is caused by UV lesions over time, by wear and body damage or by product of metabolism. Other theories view aging as a predetermined process controlled by genes.
However, no process can explain all the changes of aging. Aging is a complex process that varies in how it affects different people and even different organs. Most gerontologists (people who study aging) believes that aging is due to the interaction of many influences throughout life. These influences include heredity, environment, culture, food, exercise, fun, past illnesses, and many other factors.
Unlike the changes of adolescence, which are predictable until a few years, each person ages at a single rate. Some systems even begin to age at age 30, while other aging processes are not common until much later of life.
Although some changes always occur with aging, it occur at different rates and magnitudes. There is no way to predict exactly how you will age.
TERMS
- Atrophy
- Cells shrink. If enough cells decrease in size, the entire organ atrophies. This is often a normal aging change and can occur in any tissue. It is more common in skeletal muscle, heart, brain and sexual organs (like breasts).
- Atrophy cause is unknown, but may include the reduced use, reducing the workload, reduced blood supply or nutrition of cells, and the decreased nerve or hormonal stimulation.
- Hypertrophy
- The cells are enlarged. This is caused by an increase of protein in the celular walls and structures, and is not an increased of cell liquid.
- When some cells atrophy, others may hypertrophy to compensate the loss of cell mass.
- Hyperplasia
- Increase in the number and rate of cells division.
- Hyperplasia usually occurs to compensate for the loss of cells and allows some organs and tissues to regenerate, including the skin, the lining of the intestines, liver and bone marrow. The liver is especially good in regeneration as it can replace up to 70 % of its structure within two weeks after injury.
- Tissues that have limited capacity to regenerate include bone, cartilage and smooth muscle (such as the muscles around the intestines). Tissues that rarely or never regenerate include the nerves, skeletal muscle, myocardium and lens of the eye. When injured, these tissues are replaced with scar tissue.
- DISPLASIA
- The size, shape or organization of mature cells becomes abnormal, that is also called atypical hyperplasia.
- Dysplasia is common in cells of the cervix and the lining of the respiratory tract.
- NEOPLASIA
- Formation of tumors, either cancerous (malignant) or noncancerous (benign).
- The neoplastic cells grow rapidly, and also may have unusual shapes and abnormal functions.
Taken from: http://www.nlm.nih.gov/medlineplus/spanish/ency/article/004012.htm