As an infant is born, and the first breath is taken, many dramatic changes occur.
Effects
of Aging on the Vascular System
As an infant is born, and the first breath is taken, many
dramatic changes occur. The lungs and pulmonary vessels expand. There is a
sudden decline in resistance within the pulmonary circuit. Blood moves quickly
into the pulmonary vessels. In just a few seconds, ris-ing oxygen levels
stimulate the ductus
arteriosus to constrict. This isolates the pulmonary and aor-tic
trunks from each other. Pressure rises in the left atrium, and the valvular
flap closes the foramenovale
. The site of the foramen ovale will, in adult-hood, be marked by
a shallow depression in the inter-atrial septum known as the fossa ovalis. Throughout life, the
remnants of the ductus arteriosus will appear as a fibrous cord called the ligamentum arteriosum.
Problems will eventually develop if normal cardio-vascular
changes do not occur at birth or shortly there-after. These problems are
related to which connection remains open, and how large the opening is.
Surgery may be required to close the ductus arteriosus, the foramen ovale, or
both. Additional congenital heart defects occur due to abnormal cardiac
development, or because of inappropriate connections between the heart and its
major veins and arteries. Common con-genital heart defects include patent
foramen ovale, pat-ent ductus arteriosus, tetralogy of Fallot, ventricular
septal defect, atrioventricular septal defect, and trans-position of the great
vessels.
In the blood vessels, aging causes atherosclerosis, which
can lead to an aneurysm and resultant
stroke, myocardial infarction, or hemorrhaging. The depo-sition of calcium
salts can weaken the vessel walls to increase risk of stroke or myocardial
infarction. Ath-erosclerotic plaques can also cause the formation of thrombi.
Atherosclerosis usually begins to cause prob-lems in middle or old age.
Between ages 25 and 45, men begin to have higher rates of
developing atherosclerosis because they lack the amounts of estrogen to protect
the blood vessels, which women have. Estrogen reduces resistance to blood flow
as well as the risk of developing atherosclerosis in several ways: enhanced
production of nitric oxide, blocking of voltage-gated calcium ion channels, and
inhibition of the release of endothelin,
a protein that constricts blood vessels and raises blood pressure. Estrogen
also causes the liver to produce enzymes that increase catab-olism of
low-density lipoproteins and the production of high-density lipoproteins.
However, estrogen produc-tion begins to decline starting at age 45, and women
then have closer rates of developing atherosclerosis to men of the same age. By
age 65, men and women have the same risk for developing cardiovascular disease.
Congenital vascular problems, unlike congeni-tal heart
problems, are rare. However, aging causes venous
valves to weaken and purple varicose
veins toappear. Signs of reduced circulation include cramping of muscles
and tingling in the digits. Blood pressure also changes with age. With normal,
healthy adults under age 40, average blood pressure is 120/80 mm Hg. After this
age, hypertension occurrence is much more common, along with heart attacks,
renal failure, strokes, and vascular disease. Other factors that result in
vascular disease over our lifetimes include high- protein and high-lipid
diets, empty calorie snacks, high stress levels, lack of aerobic exercise,
smoking, and high alcohol intake. Cardiovascular disease can be prevented by
regular aerobic exercise, healthy diet, avoiding smoking, and using alcohol in
moderation.
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