The cardiovascular system, also known
as the circulatory system, is a complex
network of blood vessels, the heart,
and blood that ensures the continuous
flow of nutrients, oxygen, and waste
products throughout the body.
The Heart: The muscular organ responsible for
pumping blood.
Blood Vessels: Arteries, veins, and capillaries that form
a vast network for blood transportation.
Blood: The vital fluid carrying oxygen, nutrients,
hormones, and waste products.
Function
The circulatory system’s function is to move blood
throughout the body. This blood circulation keeps organs,
muscles and tissues healthy and working to keep you
alive.
The circulatory system also helps your body get rid of
waste products. This waste includes:
Carbon dioxide from respiration (breathing).
Other chemical byproducts from your organs.
Waste from things you eat and drink.
Anatomy Of The Heart
The heart weighs between 7 and 15
ounces (200 to 425 grams) and is a little
larger than the size of your fist. By the
end of a long life, a person’s heart may
have beat (expanded and contracted)
more than 3.5 billion times. In fact, each
day, the average heart beats 100,000
times, pumping about 2,000 gallons
(7,571 liters) of blood.
Location and Layers
Your heart is located between your lungs in the middle of
your chest, behind and slightly to the left of your
sternum). A double-layered membrane called the
pericardium surrounds your heart like a sac. The outer
layer of the pericardium surrounds the roots of your
heart’s major blood vessels and is attached by ligaments
to your spinal column, diaphragm, and other parts of
your body. The inner layer of the pericardium is attached
to the heart muscle. A coating of fluid separates the two
layers of membrane, letting the heart move as it beats.
Chambers
Your heart has 4 chambers. The upper chambers are called the
left and right atria, and the lower chambers are called the left
and right ventricles. A wall of muscle called the septum
separates the left and right atria and the left and right
ventricles. The left ventricle is the largest and strongest chamber
in your heart. The left ventricle’s chamber walls are only about a
half-inch thick, but they have enough force to push blood
through the aortic valve and into your body.
The Heart Valves
Four valves regulate blood flow through your heart:
The tricuspid valve regulates blood flow between the right
atrium and right ventricle.
The pulmonary valve controls blood flow from the right ventricle
into the pulmonary arteries, which carry blood to your lungs to
pick up oxygen.
The mitral valve lets oxygen-rich blood from your lungs pass
from the left atrium into the left ventricle.
The aortic valve opens the way for oxygen-rich blood to pass
from the left ventricle into the aorta, your body’s largest artery.
Electrical Signals
Electrical impulses from your heart muscle (the
myocardium) cause your heart to contract. This
electrical signal begins in the sinoatrial (SA)
node, located at the top of the right atrium.
The SA node is sometimes called the heart’s
“natural pacemaker.” An electrical impulse from
this natural pacemaker travels through the
muscle fibers of the atria and ventricles,
causing them to contract. Although the SA node
sends electrical impulses at a certain rate, your
heart rate may still change depending on
physical demands, stress, or hormonal factors.
