the aorta (answer d)would make the problem worse. An overriding aorta
(answer a)is the second best answer. An aortic aneurysm (answer e)is
unlikely to be present in a newborn.
357.The answer is c.(Moore and Dalley, pp 157–158.)The great cardiac
vein accompanies the anterior interventricular (descending) artery. The ante-
rior cardiac veins (answer a)pass across the right coronary sulcus to drain
directly into the right atrium. The small cardiac vein (answer e)accompa-
nies the right marginal vein and the right coronary artery. The coronary
sinus(answer b),accompanying the circumflex artery in the left coronary
sulcus, receives the great, middle (answer d),and small cardiac veins
(answer e)before draining into the right atrium.
358.The answer is c.(Moore and Dalley, pp 160–161.)In a coronary
bypass procedure a blood vessel is added to allow blood to flow distal to
the occluded coronary artery. This is generally done by removing the inter-
nal thoracic artery, which runs along the inner surface of the sternum. Its
proximal end is attached to the ascending aorta and its distal end is con-
nected to the occluded coronary artery, just distal to the blockage, thus
bypassing the problem. Remember that the internal thoracic artery sup-
plies blood to each subcostal artery, which are branches of the thoracic
aorta. All of the other answers (answers b, d)involve attaching the blood
vessel to a venous structure or in the case of the pulmonary trunk (answer a)
attaching to relatively unoxygenated blood, which is not done.
359.The answer is c.(Moore and Dalley, pp 167–168.)Heart sounds orig-
inate from the closure of the atrioventricular and semilunar valves as a
result of relative pressure reversals during the cardiac cycle. The first heart
sound, heard just after the ventricles begin to contract, occurs when ven-
tricular pressures exceed atrial pressures and thereby, closes the atrioven-
tricular valves. Reverberation within the ventricles causes this S 1 sound
(“Lub”) to have a low frequency and a relatively long duration. The second
heart sound is heard at the beginning of ventricular diastole, when the aor-
tic and pulmonary pressures exceed the respective ventricular pressures
and snap the aortic and pulmonary semilunar valves shut. This S 2 (“Dup”)
is relatively sharp when both aortic and semilunar valves close together.
However, deep inspiration, which lowers intrathoracic pressure, results in
delayed closing of the pulmonary valve and thus produces a split S 2.
Thorax Answers 487