The human Body (Home)
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Did you know..
..at rest, the heart of an elite
athlete can beat as slowly as 30 beats per minute? The heart of an average adult
beats between 70 and 80 times per minute, at rest.
||The heart is a muscular structure, about
the size of a man's fist, weighing about 500 grams. It is situated between
the lungs and sternum (breast bone) and lies towards the left, protected
by the sternum and ribs.
Journey of Blood Through the Heart
and ventricle: The
heart can be divided into two halves, as each side has a slightly different
purpose to the other. Both sides are further divided into two chambers: atrium
or ventricle. Thus we have a left
atrium, a right atrium, a left
ventricle and a right ventricle. The main
functions of each are:
atrium: Entering the right atrium is
blood from the superior vena cava. This is
blood from the body, and it is low in oxygen and carries the waste products
of the body.
- Right ventricle: The
deoxygenated blood then passes a valve and enters the right
ventricle. The walls of the right ventricle
push the blood upwards, passed another valve, and into the pulmonary
artery. From here, the blood travels through the pulmonary
artery to the lungs,
where such waste products as carbon dioxide are expelled, and oxygen enters
the bloodstream. Thus the blood that leaves the lungs is high in oxygen.
This returns to the heart and passes through the pulmonary
- Left atrium: From the pulmonary
veins, blood which is high in oxygen
enters the left atrium. It passes through a
valve and enters the..
- Left ventricle: From here,
it gets pumped upwards into the aorta, which
carries the oxygen-rich blood to the rest of the body. Thus is the
journey of blood through the heart.
*Note that the pulmonary
veins are the only veins of the body to
carry oxygenated blood.
Do you notice in the diagram above that the vena
cava (in blue) appears slightly smaller than the aorta
(in red)? This is because it is a vein, and all veins
in the body have thinner walls than arteries, and
the blood within them is at a much lower pressure.
Do you notice also that the wall of the right
ventricle is slightly thinner than that of the left
ventricle? This is because the blood being pumped from the right
ventricle only travels a short distance to the lungs. Blood leaving the left
ventricle, however, requires much more force, as it needs to be
distributed to the rest of the entire body.
Within the body are two main types of blood vessels: arteries
- Arteries: These blood
vessels carry blood that is rich in oxygen (from the lungs) and high in
nutrients (from the intestines). This blood needs to be distributed
throughout the body so that the oxygen and nutrients it carries can nourish
all parts of the body.
- Veins: These
blood vessels carry blood which has already been used by the body. This
blood has little or no oxygen, and it contains waste products, such as
carbon dioxide and urea, from cell activity.
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