Aging Changes in Organs, Tissue, and Cells: A Complete Guide

Understanding aging changes organs tissues is important for seniors and their caregivers. all vital organs begin to lose some function as you age. There are many different types of cells, but all have the same basic structure. Aging changes occur 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. The different kinds of tissues group together to form organs.

There are four basic types of tissue:

Connective tissuesupports other tissues and binds them together. Tissues are layers of similar cells that perform a specific function. The skin and the linings of the passages inside the body, such as the gastrointestinal system, are made ofepithelialtissue.

Muscle tissueincludes three types of tissue:

– Striated muscles, such as those that move the skeleton (also called voluntary muscle)
– Smooth muscles (also called involuntary muscle), such as the muscles contained in the stomach and other internal organs like the female uterus
– Cardiac muscle, which makes up most of the heart wall (also an involuntary muscle)

Nerve tissueis made up of nerve cells (neurons) and is used to carry messages to and from various parts of the body. This includes bone, blood, and lymph tissues, as well as the tissues that give support and structure to the skin and internal organs.

Epithelial tissueprovides a covering for superficial and deeper body layers. All cells experience changes with aging. The brain, spinal cord, and peripheral nerves are made of nerve tissue.

AGING CHANGES

Cells are the basic building blocks of tissues. Among other changes, there is an increase in pigments and fatty substances inside the cell (lipids). They become larger and are less able to divide and multiply. A fatty brown pigment called lipofuscin collects in many tissues, as do other fatty substances.

Connective tissue changes, becoming more stiff. Many cells lose their ability to function, or they begin to function abnormally.

As aging continues, waste products build up in tissue. Cell membranes change, so many tissues have more trouble getting oxygen and nutrients and removing carbon dioxide and other wastes.

Many tissues lose mass. This makes the organs, blood vessels, and airways more rigid. Some tissues become lumpy (nodular) or more rigid.

Because of cell and tissue changes, your organs also change as you age. This process is called atrophy. Most people do not notice this loss immediately, because you rarely need to use your organs to their fullest ability.

Organs have a reserve ability to function beyond the usual needs. Aging organs slowly lose function. After age 30, an average of 1% of this reserve is lost each year.

The biggest changes in organ reserve occur in the heart, lungs, and kidneys. For example, the heart of a 20-year-old is capable of pumping about 10 times the amount of blood that is actually needed to keep the body alive. When an organ is worked harder than usual, it may not be able to increase function. The amount of reserve lost varies between people and between different organs in a single person.

These changes appear slowly and over a long period. Things that produce an extra workload (body stressors) include the following:

– Illness
– Medicines
– Overactive thyroid gland
– considerable life changes
– Sudden higher physical demands on the body, such as a change in activity or exposure to a higher altitude

Loss of reserve also makes it harder to restore balance (equilibrium) in the body. Sudden heart failure or other problems can develop when the body is worked harder than usual. Lower doses of medicines may be needed, and side effects become more common. Medicines are removed from the body by the kidneys and liver at a slower rate. Some medicines have entirely different side effects in the elderly than in younger people.

AGING THEORY

No one knows how and why people change as they get older. Recovery from some illnesses may be less than 100%, leading to more and more disability.

Side effects of medicine can mimic the symptoms of many diseases, so it is easy to mistake a medicine reaction for an illness. Other theories view aging as a predetermined process controlled by genes.

No single known process can explain all the changes of aging. Some theories claim that aging is caused by injuries from ultraviolet light over time, wear and tear on the body, or byproducts ofmetabolism. Most gerontologists (people who study aging) feel that aging is due to the interaction of many lifelong influences. Aging is a complex process that varies as to how it affects different people and even different organs. Some systems begin aging as early as age 30. These influences include heredity, environment, culture, diet, exercise and leisure, past illnesses, and many other factors.

Unlike the changes of adolescence, which are predictable to within a few years, each person ages at a unique rate. There is no way to predict exactly how you will age.

TERMS TO DESCRIBE TYPES OF CELL CHANGES

Atrophy:

– Cells shrink. Other aging processes are not common until much later in life.

Although some changes always occur with aging, they occur at different rates and to different extents. This is often a normal aging change and can occur in any tissue. If enough cells decrease in size, the entire organ atrophies. Bones become thinner and more likely to break with minor trauma. It is most common in skeletal muscle, the heart, the brain, and the sex organs (such as the breasts and ovaries).

Hypertrophy:

– Cells enlarge. – The cause of atrophy is unknown, but may include reduced use, lower workload, lower blood supply or nutrition to the cells, and reduced stimulation by nerves or hormones. – When some cells atrophy, others may hypertrophy to make up for the loss of cell mass. This is caused by an increase of proteins in the cell membrane and cell structures, not an increase in the cell’s fluid. There is an higher rate of cell division.

Hyperplasia:

– The number of cells increases. It allows some organs and tissues to regenerate, including the skin, lining of the intestines, liver, and bone marrow. – Hyperplasia usually occurs to compensate for a loss of cells. It can replace up to 70% of its structure within 2 weeks after an injury.

The liver is especially good at regeneration. Ongoing research suggests that tissues previously thought to have limited or no ability to regenerate – nerves, skeletal muscle, heart muscle, and the lens of the eye – may have some regenerative ability. – Tissues that have limited ability to regenerate include bone, cartilage, and smooth muscle (such as the muscles around the intestines).

Dysplasia:

– The size, shape, or organization of mature cells becomes abnormal. But in most cases we have not yet learned how to harness this ability for medical treatment. – Dysplasia is fairly common in the cells of the cervix and the lining of the respiratory tract. This is also called atypical hyperplasia. – Neoplastic cells often reproduce quickly.

Neoplasia:

– The formation of tumors, either cancerous (malignant) or noncancerous (benign).

As you grow older, you will have changes throughout your body, including changes in your:

– Hormone production
– Immunity
– Skin
– Sleep
– Bones, muscles, and joints
– Breasts
– Face
– Reproductive system – female
– Reproductive system – male
– Heart and blood vessels
– Kidneys
– Lungs
– Nervous system

– Tissue types

Baynes JW. They may have unusual shapes and abnormal function. In: Baynes JW, Dominiczak MH, eds.Medical Biochemistry. Aging. Philadelphia, PA: Elsevier; 2023:chap 29.

Walston JD. 6th ed. In: Goldman L, Cooney KA, eds.Goldman-Cecil Medicine. Common clinical sequelae of aging. Philadelphia, PA: Elsevier; 2024:chap 24.

Updated by: Frank D. 27th ed. Also reviewed by David C. Brodkey, MD, FCCM, Associate Professor, Section of Pulmonary and Critical Care Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI. Editorial team.

Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M.