Download Cardiocascular System Worksheet Reading CV Worksheet Reading

Cardiovascular System
The Cardiovascular System is a body system that consists of the heart,
blood vessels, and blood. The Heart is a muscular pump that beats continuously
and rhythmically to send blood to the body. The heart is surrounded and protected
by a sac called the pericardium. The Pericardium is a membranous bag that
completely envelops the heart. Within the heart are four chambers, two atria and
two ventricles. A wall called the septum separates the two sides. The atria are
upper chambers and receive blood returning to the heart. The ventricles are lower
chambers that pump blood from the heart. The heart beats an average of seventy to
eighty times per minute. Blood pressure is the force exerted by the flowing blood
against the walls of the arteries. The pumping action of the heart creates the force.
Every time the heart beats, the pressure increases. When the heart muscle relaxes
between beats, the pressure decreases.
Blood is continually circulating from the left ventricle to all body cells and
back to the right atrium. This blood that is rich in oxygen is pumped through the
aorta. The aorta is the main artery of the body. This blood circulates to all body
cells providing them with nutrients and oxygen. At the same time, carbon dioxide,
which is a waste product of cell metabolism, and other wastes move from the cells
through cell membranes into circulating blood. This blood returns to the right
atrium through large veins, the superior and inferior vena cava. This is systemic
circulation.
Blood also is continually circulating from the right ventricle to the lungs and
back to the left atrium. This is pulmonary circulation. Blood returning to the right
atrium in systemic circulation flows into the right ventricle, which contracts and
pumps the blood to the lungs. In the lungs, an exchange of gases occurs. This
blood, which is rich in carbon dioxide, moves through cell membranes into lung
cells and at the same time oxygen moves from lung cells into the circulating blood.
The oxygen in the lung cells is the result of a person’s inhaling. The blood now
rich in oxygen returns to the left atrium and flows into the left ventricle and
systemic circulation starts again. As the person exhales, carbon dioxide is removed
from the body.
There are three main types of blood vessels- arteries, veins, and capillaries.
Arteries are blood vessels that carry blood away from the heart. Veins are blood
vessels that carry blood toward the heart. In systemic circulation, blood flows
through the aorta and other arteries to all parts of the body. In pulmonary
circulation, blood flows through the pulmonary artery to the lungs. Near the heart,
arteries are large, muscular, and have thick walls. Away from the heart, large
arteries continually subdivide into smaller arteries called arterioles. An arteriole
is a blood vessel that branches off an artery to link it to a capillary. A capillary is a
microscopic, thin-walled blood vessel through which materials can be exchanged
with the blood. Capillaries connect arterioles to small veins called venules. Blood
flowing through venules and veins is being returned to the right and left atria.
Blood is the fluid that supplies essential substances to all body cells and
removes waste products from all body cells. Plasma is the fluid part of blood that
remains if the blood cells are removed. Plasma is about 90 percent water. Red
blood cells, white blood cells, and platelets are immersed in the plasma. Red blood
cells contain hemoglobin. Hemoglobin is a substance that combines with oxygen
and gives blood its red color. Red blood cells are the most numerous cells in blood
and they carry oxygen. New red cells are continually being produced in bone
marrow. White blood cells are cells that destroy pathogens that enter the body.
They are produced in bone marrow and in lymph nodes. The number of white
blood cells increases when pathogens enter the body. White blood cells surround
and destroy pathogens. Platelets are small fragments in the blood, shaped like
disks that help prevent blood loss from injured blood vessels. Platelets help form
clots, which seal holes in blood vessels and stop bleeding.
Since blood pressure varies from person to person and within the same
person, it is essential to have blood pressure checked. A person can have high
blood pressure and not know it. Continued high blood pressure is the most
common disease affecting the heart and blood vessels and can lead to serious
health problems. Ways to take care of the cardiovascular system are to avoid
smoking, reduce the amount of fat and salt in the diet, and get enough exercise and
rest.