Heart
The heart is a mostly
hollow, muscular organ composed of cardiac muscles and connective tissue that
acts as a pump to distribute blood throughout the body’s tissues.
The heart is the epicenter of the circulatory system, which
supplies the body with oxygen and other important nutrients needed to sustain
life.
The heart has a double-pump feature that transports blood away
from it and back to it. Freshly oxygenated blood leaves the left side of the
heart through the ascending aorta—the largest artery in the human body. Blood
flowing through the right side of the heart is returning from all over the body
before it is sent to the lungs where it receives oxygen.
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The heart has three layers. They are the:
·
Epicardium: This thin membrane is the outer-most layer
of the heart.
·
Myocardium: This thick layer is the muscle that
contracts to pump and propel blood through the body’s tissues.
·
Endocardium: The innermost layer is thin and smooth.
The heart is divided into four chambers: two atria and two
ventricles. Blood is transported through the body via a complex network of
veins and arteries.
The average human heart weighs between 6 and 11 ounces. The
muscle is strong enough to pump up to 2,000 gallons — as much as a fire
department’s tanker truck — of blood through one’s body every day.
The average heart beats between 60 and 90 times per minute, but
this depends on a person’s cardiovascular health and activity level. The more
physically fit people are, the lower their resting heart rates will be.
Hormones released because of emotions and other stimuli affect
the heart rate, which is why the heart was historically associated with
emotions.
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