Preventing Problems with the Human Circulatory System
Within a month of conception, the cluster of cells that will, in the course of
time, become a human being begins throbbing, signaling the development of
a primitive heart. Scarcely four weeks more pass before an intricate network
of veins and arteries the size of a pea forms and subdivides into a tiny replica
of the four chambers that will one day make up the adult heart. As the fetus
grows, so does its vitally important circulatory system. Although most of the
functions of the heart remain dependent upon the mother throughout the
entire pregnancy, in the latter stages the organ becomes strong enough to beat
on its own. Even so, until birth the baby is cared for and nourished through
the mother's placenta. An umbilical cord provides a supply line that furnishes
food and oxygen for the baby, and also removes waste. When at last the
birthing moment arrives, the baby emerges a separate individual; almost as
soon as its first cries are sounded, its pulmonary and circulatory systems
undergo a change that renders them self-sufficient.
How it Works
Technically speaking, the circulatory system is a masterpiece of organic
activity. Composed of a network of 60,000 miles of blood vessels and a
pintsized, powerhouse pump known as the heart, it services more than 2,000
gallons of blood per day, feeding and replenishing other organs and making
In an adult, the heart is normally an 11 - ounce, fistsized organ that literally
pushes blood through arteries, veins and capillaries. It does this by means of
muscular contractions sparked by electrical impulses from the heart's
pacemaker (sinoatrial node). All of the cells within each of the chambers
magically work on cue. First, the right side sends blood to the lungs.
There carbon dioxide is removed and oxygen is added, turning the blood a
bright red color. Then the blood is pumped to the left side of the heart and
sent via the aorta to the rest of the body.
To survive, each of the body's approximately 1 billion cells must be
nourished. This is the job of the blood, with the heart and vessels acting as
facilitators. After depositing the necessary nutrients with each of the cells, the
blood returns to the heart, carrying with it waste products it has picked up
along the way. These are eliminated through a filtering process in the lungs
By now the supply of oxygen within the blood is nearly exhausted, and it is
time to restock its supplies and begin the journey again. Incredibly, the whole
process has taken just 20 seconds.
During the course of an average life, the heart pumps tens of millions of
gallons of blood. It is estimated that the amount would easily fill a
24-foot-wide cylinder to a height greater than the Empire State
Perhaps more impressively, the circulatory system has the computer-like
ability to direct greater and lesser amounts of blood to various areas of...