Page 1665 - Saunders Comprehensive Review For NCLEX-RN

artery.
3. The left atrium receives oxygenated blood from the
lungs via 4 pulmonary veins.
4. The left ventricle is the largest and most muscular
chamber; it receives oxygenated blood from the lungs
via the left atrium and pumps blood into the systemic
circulation via the aorta.
D. There are 4 valves in the heart.
1. There are 2 atrioventricular valves, the tricuspid and
the mitral, which lie between the atria and ventricles.
a. The tricuspid valve is located on the
right side of the heart.
b. The bicuspid (mitral) valve is located
on the left side of the heart.
c. The atrioventricular valves close at the
beginning of ventricular contraction
and prevent blood from flowing back
into the atria from the ventricles; these
valves open when the ventricles relax.
2. There are 2 semilunar valves, the pulmonic and the
aortic.
a. The pulmonic semilunar valve lies
between the right ventricle and the
pulmonary artery.
b. The aortic semilunar valve lies between
the left ventricle and the aorta.
c. The semilunar valves prevent blood
from flowing back into the ventricles
during relaxation; they open during
ventricular contraction and close when
the ventricles begin to relax.
E. Sinoatrial (SA) node
1. The main pacemaker that initiates each heartbeat
2. It is located at the junction of the superior vena cava
and the right atrium.
3. The SA node generates electrical impulses at 60 to 100
times per minute and is controlled by the sympathetic
and parasympathetic nervous systems.
F. Atrioventricular (AV) node
1. Located in the lower aspect of the atrial septum
2. Receives electrical impulses from the SA node
3. If the SA node fails, the AV node can initiate and
sustain a heart rate of 40 to 60 beats per minute.
G. The bundle of His
1. A continuation of the AV node; located at the
interventricular septum
2. It branches into the right bundle branch, which
extends down the right side of the interventricular

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