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CARDIOVASCULAR SYSTEM
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•eN: Use blue for A-A4. red for H-~.
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and your fightest colors for B. C. I.
·and J. All dotted arrows (A4) receiye a blue color; all clear alrows (Hi
· receiVe a red color. (1) Begin with the allOWS A4above the tltle list and
abOve the superior vena cava (A) in the Illustration at upper right and color
the structures In the order of the title list (A-H;. (2) Color the circulation
chart at lower right. beginning with the arrow A4 leading into the right atrium
(numeral 1). Color the numerals in Older from 1 10 4 and related arrows.
00 not color Ihe chambers or the vessels In this drawing at lower right
ANTERIOR VIEW OF HEART CAVITIES AND GREAT VESSELS Lal! common carolid artery
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CIRCULATION THROUGH THE HEART The heart is the muscular pump of the blood vascular system. It Contains four cavities (chambers): two on the right side {pulmonary heart), two on the left (systemic heart). The pulmonary "heart" @~§CA!JoOOD@GO @(b@)@@) 1!4£!>
includes the right atrium and right ventricle. The lhln-walled right atrium receives poorly oxygenated blood from the superior and the ~G!10~ IDl:1@@@)A't-et>
inferior vena cava and from the coronary sinus (draining the heart vessels). The thin-walled left atrium receives richly oxygenated blood from pulmonary veins. Atrial blood Is pumped at a pressure 01 about 5 mm Hg into the right and left ventricles simultaneously through the atrioventricular orilices, guarded by the 3-cusp tricus­
pid valve on the right and the 2-cusp bicuspid valve on the lefl. The cusps are like panels of a parachute. secured to the papillary mus­
cles in the ventricles by tendinous chOrdae tendin8a8. These mus­
cles contract with the ventricular muscles, tensing the cords and resisting cusp over-flap as ventricular blood bulges into them dur­ Ing ventricular contraction (systole). The right venlricle pumps oxy­
gen-deflcient blood to the lungs via the pulmonary trunk at a pressure of about 25 mm Hg (right ventricle). and the left ventricle pumps oxygen-rich blood Into the sscendlng sorta at a pressure of about 120 mm Hg simultaneously. This pressure diHerence is reflected!n the thicker walls 01 the left ventricle compared to the right. The pocket-like pulmonary snd aortic semilunar valves guard the trunk and aorta, respectively. As blood falls back toward the ventricle from the trunk/aorta during the resting phase (diastole). these pockets fill. closing off their respective orifices and prevent­
ing reflux into the ventricles. 1:
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SYSTEM
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blue ror D and red ror E. Use a very light color for B so that the patterns
1de~ltlfying the segments (s-s3l of the ECG remain visible after colorin~.
right and color the lour large arrows identifying the atria (A l
aa well aa Ihelr titles. 'The atria and ventricles are not to be
In the middle 01 the page, color the stages 01 blood flow through Ihe
related lettars. These stages relate to voltage changes in the ECG
Color the ECG and related letters. starting at the left and working to the
parts oIlhe ECG are related to Ihe activity 01 the conduction system or
myocardial activity. (4) Color the horizontal bar below the lime line.
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muscle cells contract spontaneously. They do not require motor
10 shorten. However, the intrinsic contraction rate of these cells Is
and too unorganized for effective pumping of the heart. Happily.
of more excitable but non-contractile cardiac cells take responsi­
initialing and conducting electrochemical impulses throughout the
musculature. Such cells effect a coordinated, rhythmic sequence
muscle Contractions that result in blood being moved through
of the heart with appropriate volumes and pressures. These
coostltule the cardiac conduction system. Impulses generated at
(SA) node are distributed throughout the atria and to the
.ntflCI!JISr (AV) node by way of non-discrete internodal pathways.
travel Irom the AV node, down theAV bundle and its branches,
Purkinje plextls of cells embedded in the ventricular musculature.
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(R) INTERVAL ~ t
cardiac conducllon system generates voltage changes about the heart,
of which can be monitored. assessed, and measured by electrocar­
(ECG). An ECG is essentially.a voltmeter reading. It does not
hemodynamic changes. Electrodes are placed on a number of
points on the skin. Recorded data (various waves of varying voltage
time) are displayed on an oscilloscope or a strip 01 moving paper.
and direction of wave deflections are dependent upon the spatial
IBtltil1AAinof the electrodes (leads) on the body surface.
the SA node fires, excitation/depolarization of the atrial musculature
out from the node. This Is reflected In the ECG by an upward defllllc­
the resting (isoelectrlc) horlzontailine (P wave). This deflection imme­
precedes the contraction of tine atrial musculature and filling of th~57
The P-O interval (P-R interval in the absence of a a wave) renems
QT INTERVAL
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conduction of excitation from tine atria to the Purkln]e cell plexus in the ven­
tricular myocardium. Prolongation of this interval beyond .20 seconds may
reflect an AV conduction biock. The QRS complex reflects depolarization
of the ventricular myocardium. This complex of deflections immediately
precedes venlricular contraction. wherein blood is forced into the pulmonary
trunk and ascending aorta. The S-T segment reflects a continuing period of
ventricular depolarization. Myocardial ischemia may induce a deflection
of this normally horizontal segment. The T wave Is an upward, prolonged
deflection and reflects ventricular repolarization (recovery), during which the
atria passively fill with blood from the vena cavae and pulmonary veins. The
aT interval, corrected for heart rate (aTe). reflects ventricular depolarization
and repolarization. Prolongation 01 this segment may suggest abnormal
ventricular rhythms (arrhythmias). In a healthy heart at a low rate of beat.
the P-O, S·T, and T-P se~ments all are isoelectric (horizontal).