How It Works
The heart can be thought of as a factory. Many things
need to be working in sync and functioning well in order
to have a good product. For the heart to do its job well —
providing oxygen and nutrients for the body — these need
to be working:
Structure for blood flow
Muscle for pumping
Electrical system for direction
Plumbing for its energy source
The heart is about the size of your fist and lies beneath the
breastbone. It is surrounded by the rib cage for protection.
The heart muscle has three layers:
Epicardium — outer layer
Myocardium — middle layer
Endocardium — inner layer
A sac around the heart called the pericardium holds a
small amount of fluid. The fluid lubricates and protects the
heart as it beats.
Heart Chambers
The heart is divided into four chambers:
Atria — two upper chambers contract or squeeze together to pump blood into the
ventricles or lower chambers.
Ventricles — two lower