Human Heart Facts
· The human heart provides a continuous blood circulation through
the cardiac cycle and is one of the most vital organs in the human
· It is divided into four chambers: the two upper chambers are called
the left and right atria and two lower chambers are called the right and
· Normally the right ventricle pumps the same blood amount into
the lungs with each bit that the left ventricle pumps out.
· Physicians commonly refer to the right atrium and right ventricle
together as the right heart and to the left atrium and ventricle as
the left heart.
· The electric energy that stimulates the heart occurs in the sinoatrial
node, which produces a definite potential and then discharges, sending
an impulse across the atria.
· The Purkinje fibers transmit the electric charge to
the myocardium while the cells of the atrial walls transmit it from cell
to cell, making the atrial syncytium.
· The human heart and its disorders (cardiopathies) are studied
primarily by cardiology
· Blood flows through the heart in one direction, from the atrias to
the ventricles, and out of the great arteries, or the aorta for example.
· Blood is prevented from flowing backwards by the triscupid, mitral,
aortic, and pulmonary valves.
· The function of the right side of the heart (see right heart) is to
collect de-oxygenated blood, in the right atrium, from the body (via
superior and inferior vena cavae) and pump it, via the right ventricle,
into the lungs (pulmonary circulation) so that carbon dioxide can be
dropped off and oxygen picked up (gas exchange).
· This happens through the passive process of diffusion.
· The left side (see left heart) collects oxygenated blood from
the lungs into the left atrium.
· From the left atrium the blood moves to the left ventricle which
pumps it out to the body (via the aorta).
· On both sides, the lower ventricles are thicker and stronger than
the upper atria.
· The muscle wall surrounding the left ventricle is thicker than the
wall surrounding the right ventricle due to the higher force needed to
pump the blood through the systemic circulation.
· Starting in the right atrium, the blood flows through the tricuspid
valve to the right ventricle.
· Here, it is pumped out the pulmonary semilunar valve and travels
through the pulmonary artery to the lungs.
· From there, blood flows back through the pulmonary vein to the
· It then travels through the mitral valve to the left ventricle, from
where it is pumped through the aortic semilunar valve to the aorta and
to the rest of the body.
· The (relatively) deoxygenated blood finally returns to the heart
through the inferior vena cava and superior vena cava, and enters the
right atrium where the process began.
· The human heart is about the size of a fist and has a mass of
between 250 and 350 grams.