A Kid's Guide to the Cardiovascular/Circulatory System
Ever wonder what makes your heart beat? The heart is a part of the cardiovascular,
or circulatory system, which is the body's main form of transportation for important
organic materials. In addition to the heart, the cardiovascular system is also made
up of blood and blood vessels. One of its most important functions is to deliver
oxygen to all the cells
in your body and remove its waste. As you inhale, oxygen enters your lungs. At the
same time, the heart pumps blood to the lungs to absorb that oxygen. The blood,
now oxygen-rich, then travels all over the body through blood vessels and delivers
the oxygen to the muscles and absorbs the carbon dioxide waste before returning
to the heart. Taking good care of your circulatory system will lead to a healthier
heart and a better lifestyle.
The heart is both the starting and finishing point of the
cardiovascular system. The
heart is a muscle size of your fist that acts as a pump delivering blood
around the body. It is made up of four chambers. The top two chambers are called
atria (one chamber is called an atrium), and the bottom two are called
ventricles. When blood enters the heart, it fills up the atrium during a resting
stage known as diastole. Then, the atrium releases the blood into the ventricle
below, which then pumps the blood out of the heart. This pumping action in which
the ventricles contract is known as systole. Because the ventricles do all
the work, they have much thicker walls than the atria.
When your heart beats, it is going through the
stages of diastole and systole.
Additionally, there are
that prevent the blood from flowing backwards. The heart is also separated into
the left side and right side by a wall of special muscle known as the septum.
This distinction is important, because
side has its own special function. The left side of the heart contains oxygen-rich
blood and pumps it to the body. The right side contains oxygen-poor blood and pumps
it to the lungs, where it receives more oxygen.
Blood vessels are
essentially a network of tubes that the blood travels through to get to different
parts of the body. If you think of your body as a city, the different types of vessels
are like the highways, streets and roads. The three main types of blood vessels
include arteries, veins and capillaries. Arteries are thick walled vessels
that bring blood away from the heart, while veins bring blood towards the
are extremely small blood vessels; many of them are only one cell thick! These
tubes are tiny, but still very important. Capillaries are the place for
gas exchange, where nutrients are delivered and wastes are removed. When it
reaches the tissues in your body, it gives oxygen to the tissue and takes away the
carbon dioxide waste. The blood containing carbon dioxide goes to the lungs and
gets breathed out as you exhale. Because blood carries heat, blood vessels are also
an important part of the body's temperature regulation. When it's cold outside the
vessels become narrower in order to keep the blood flow closer to the heart and
organs, rather than to the extremities such as fingers and toes. This narrowing
is known as vasoconstriction. The opposite process is called vasodilation,
where the blood vessels widen to allow more blood flow. This helps cool the body
down when it’s hot outside, because heat is lost by circulating the blood to the
If the blood vessels are like the highways, then the
is like the traffic. Just as there are different types of vehicles on the road,
there are different
types of cells in your blood.
Red blood cells
are the oxygen carrying cells, and
give blood its
red color. Another fancy name for red blood cells is erythrocytes.
blood cells , which are also known as leukocytes, protect the
body against diseases by fighting germs.
are the cells responsible for
blood clotting. Have you ever thought about why scabs are formed after you get
a cut or scrape? Platelets are the ones that cause this important process.
When the body gets injured, platelets come together and form a substance called
fibrinogen, which forms clots and stops the bleeding. Without this process,
blood would just keep flowing.
Plasma is the
colorless liquid portion of the blood that contains the red blood cells, white blood
cells, and platelets. The plasma is made up of water, salts, minerals, vitamins,
hormones, gases and fats.
Because of its important functions, it's important to keep the cardiovascular
system strong and healthy.
right foods reduces the chances of
and keeps the circulatory system running smoothly. Eat plenty of
and vegetables, and try to stay away from junk foods that are high in saturated
fats and trans fats. Another part of a healthy cardiovascular system is
regular exercise. Running in the park or playing sports with friends, for instance,
is a fun way to keep your circulatory system active and healthy.