The heart has two sides. The right side pumps blood to the lungs
to receive oxygen and get rid of carbon dioxide. The left side
pumps oxygen-rich blood to the body.
Blood flows out of the heart through arteries, which branch out
and get smaller and smaller as they go into the tissues. In the
tissues, they become tiny capillaries.
Capillaries are where the blood gives up oxygen and nutrients to
the tissues, and receives carbon dioxide and wastes back from the
tissues. Then, the vessels begin to collect together into larger
and larger veins, which return blood to the heart.
AGING CHANGES
Heart:
- The heart has a natural pacemaker system that controls the
heartbeat. Some of the pathways of this system may develop fibrous
tissue and fat deposits. The natural pacemaker (the SA node) loses
some of its cells. These changes may result in a slightly slower
heart rate.
- A slight increase in the size of the heart, especially the left
ventricle occurs in some people. The heart wall thickens, so the
amount of blood that the chamber can hold may actually decrease
despite the increased overall heart size. The heart may fill more
slowly.
- Heart changes cause the ECG of a normal, healthy older person
to be slightly different than the ECG of a healthy younger adult.
Abnormal rhythms (arrhythmias), such as atrial fibrillation, are
more common in older people. They may be caused by heart
disease.
- Normal changes in the heart include deposits of the "aging
pigment," lipofuscin. The heart muscle cells degenerate slightly.
The valves inside the heart, which control the direction of blood
flow, thicken and become stiffer. A heart murmur caused by valve
stiffness is fairly common in older people.
Blood vessels:
- Receptors called baroreceptors monitor the blood pressure and
make changes to help maintain a fairly constant blood pressure when
a person changes positions or is doing other activities. The
baroreceptors become less sensitive with aging. This may explain
why many older people have orthostatic hypotension, a condition in
which the blood pressure falls when a person goes from lying or
sitting to standing. This causes dizziness because there is less
blood flow to the brain.
- The capillary walls thicken slightly. This may cause a slightly
slower rate of exchange of nutrients and wastes.
- The main artery from the heart (aorta) becomes thicker,
stiffer, and less flexible. This is probably related to changes in
the connective tissue of the blood vessel wall. This makes the
blood pressure higher and makes the heart work harder, which may
lead to thickening of the heart muscle (hypertrophy). The other
arteries also thicken and stiffen. In general, most older people
have a moderate increase in blood pressure.
Blood:
- The blood itself changes slightly with age. Normal aging causes
a reduction in total body water. As part of this, there is less
fluid in the bloodstream, so blood volume decreases.
- The speed with which red blood cells are produced in response
to stress or illness is reduced. This creates a slower response to
blood loss and anemia.
- Most of the white blood cells stay at the same levels, although
certain white blood cells important to immunity (neutrophils)
decrease in their number and ability to fight off bacteria. This
reduces the ability to resist infection.
EFFECT OF CHANGES
Normally, the heart continues to pump enough blood to supply all
parts of the body. However, an older heart may not be able to pump
blood as well when you make it work harder.