• The adult heart is approx.
the size of a closed fist. It
resides in the thoracic
cavity between the lungs
in an area called the
mediastinum. The top is
rounded and called the
base, the bottom has a
point called the apex.
Anatomy of Heart
• Outermost is the
pericardium – or
pericardial sac: double
layered – tough fibrous
• Visceral – on heart surface
• Parietal – towards the
• Pericardial cavity –
pericardial fluid - serous
Middle Layer – myocardium – muscular layer
Muscle cells are connected via intercalated discs - carry conduction
in a ‘domino effect’
Innermost layer – endocardium – epithelial layer – simple squamous
epithelium over a tough connective tissue
Valves are a result of the endocardium folding – valves between the
atrium and ventricle = AV valve, atrioventricular valve or tricuspid
[R] /bicuspid [L]. -valves between the ventricles and vessels =
semilunar valves or pulmonic [R]/aortic[L]
Chambers: right & left atria
right & left ventricles
Major Vessels: vena cava, aorta, pulmonary veins, pulmonary trunk
• Electrical conduction
of the heart can be
electrodes on body
• Not a direct measure
of mechanical events,
force of contraction or
• The normal EKG
consists of a P wave,
the QRS complex, and
a T wave.
The P wave indicates that the atria (the two upper chambers of
the heart) are contracting to pump out blood.
the "QRS complex." This part indicates that the ventricles (the
two lower chambers of the heart) are contracting to pump out
blood to the body
The ST segment indicates the amount of time from the end of
the contraction of the ventricles to the beginning of the rest
period before the ventricles begin to contract for the next beat.
The T wave indicates the resting period of the ventricles.
An arrhythmia (also called dysrhythmia) is an abnormal
rhythm of the heart, which can cause the heart to pump less
Arrhythmias can cause problems with contractions of the heart
not allowing the chambers to fill with an adequate amount of
blood, because an electrical signal is causing the heart to pump
not allowing a sufficient amount of blood to be pumped out to
the body, because an electrical signal is causing the heart to
pump too slowly or too irregularly.