The Heart
The heart is a muscular pump. It sits inside your
chest slightly to the left of centre, and is protected by your ribs . If you place
the heel of your hand in he middle of your sternum (breast bone) and your
fingers under your left breast area you can probably feel the thrust of your
heart pumping with your fingertips between the fifth and sixth ribs.
The heart is made up of four chambers
separated by valves. The top two chambers are called atria (singular is atrium – from
the Latin word for the central room in a roman house) these receive blood, and are
relatively thin walled. The right atrium receives used blood from the largest vein in the
body - the Vena Cava, following its trip round the body and the left atrium receives
freshly oxygenated blood from the lungs via the Pulomonary vein.
The atria each funnel down into a ventricle.
Ventricles are thick walled and are capable of pumping the blood a long way. The right
ventricle sends the blood to the lungs to pick up a load of oxygen via teh Pulmonary
artery and the left ventricle pumps the freshly loaded blood on its long trip round
the body via the Aorta.
To prevent blood leaking back up the system one way
valves are strategically placed between each atrium and ventricle (the mitral and
tricuspid valves) and at the root of the major blood vessels that flow into the atria and
out of the ventricles arotic and pulmonary valves - named after the artery they sit in ) .
This
animation is a schematic view of the heart at work. It represents the four chambers and
the blood vessels which feed and drain them. Blue arrows represent
blood which has returned to the heart to the right atrium after supplying the body with
oxygen to fuel cells and it is then sent to the lungs via the right ventricle. Red arrows represent
blood which has returned from the lungs, where it has received oxygen, to the left
atrium and from here it is pumped out of the right ventricle round the body.
(c) drfeelgood 1999
Heart facts :
The average adult Human Heart weighs
The Human Heart pumps over 2 billion times without a
break in a life time !
Task :
if your heart beats around 100,000 times per
day ( based on 70 beats per minute) calculate how many times your heart has beaten in your
life so far