Human heart anatomy
In humans, the heart is
roughly the size of a large fist and weighs between about 10 to 12 ounces (280
to 340 grams) in men and 8 to 10 ounces (230 to 280 grams) in women, according
to Henry Gray's "Anatomy of the Human Body."
The physiology of the
heart basically comes down to "structure, electricity and plumbing,"
Phillips told Live Science
.
.
The
human heart is about the size of a fist.Credit: tlorna |Shutterstock
The human heart has four
chambers: two upper chambers (the atria) and two lower ones (the ventricles),
according to the National Institutes of Health. The right
atrium and right ventricle together make up the "right heart," and
the left atrium and left ventricle make up the "left heart." A wall
of muscle called the septum separates the two sides of the heart.
A double-walled sac
called the pericardium encases the heart, which serves to protect the heart and
anchor it inside the chest. Between the outer layer, the parietal pericardium,
and the inner layer, the serous pericardium, runs pericardial fluid, which
lubricates the heart during contractions and movements of the lungs and
diaphragm.
The heart's outer wall
consists of three layers. The outermost wall layer, or epicardium, is the inner
wall of the pericardium. The middle layer, or myocardium, contains the
muscle that contracts. The inner layer, or endocardium, is the lining that
contacts the blood.
The tricuspid valve and
the mitral valve make up the atrioventricular (AV) valves, which connect the
atria and the ventricles. The pulmonary semi-lunar valve separates the right
ventricle from the pulmonary artery, and the aortic valve separates the left
ventricle from the aorta. The heartstrings, or chordae tendinae, anchor the
valves to heart muscles.
The sinoatrial node
produces the electrical pulses that drive heart contractions.
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