Defects of or damage to conducting system results
in cardiac arrhythmias, i.e. defects in the normal
rhythm of contraction. Except for a part of the left
branch of the AV bundle supplied by the left
coronary artery, the whole of the conducting system
is usually supplied by the right coronary artery.
Vascular lesions of the heart can cause a variety of
arrhythmias.4 The r t brnnch of the AV bundle passes down the
right side of the interventricular septum. A large part
enters the moderator band to reach the anterior wall
of the right ventricle where it divides into Purkinje
fibres.
5 The left branch of the AV bundle descends on the
left side of the interventricular septum and is
distributed to the left ventricle #ter dividing into
Purkinje fibres.
- The Purkinje fibres form a subendocardial plexus.
They are large pale fibres striated only at their
margins. They usually possess double nuclei. These
generate impulses at the rate oI20-35 beats/minute.
PERICARDIUM AND HEART1 It first passes forwards and to the right to emerge
on the surface of the heart between the root of the
pulmonary trunk and the right auricle.
2 It then runs downwards in the right anterior
coronary sulcus to the junction of the right and
inferior borders of the heart.
3 It winds round the inferior border to reach the
diaphragmatic surface of the heart. Here it runs
backwards and to the left in the right posterior
coronary sulcus to reach the posterior inter-
ventricular groove.
4 It terminates by anastomosing with the circumflex
branch of left coronary artery at the crux.Ss'*n*f:*s
I La branches
a. Marginal.
b. Posterior interventricular.
2 Small branches
a. Nodallr.60% cases.
b. Right atrial.
c. Infundibular.
d. Terminal.
e. Right ventricular
f. ConusAres *f #gs 6iff#F?
1 Right atrium
2 Ventricles
a. Greater part of the right ventricle, except the area
adjoining the anterior interventricular groove.
b. A small part of the left ventricle adjoining the
posterior interventricular groove.
3 Posterior part of the interventricular septum.
4 Whole of the conducting system of the heart except
a part of the left branch of the AV bundle. The SA
node is supplied by the left coronary artery in about
40% of cases.DISSECTIONStrip the visceral pericardium from the sternocostal
surface of the heart. Expose the anterior interventricular
branch of the left coronary artery and the great cardiac
vein by carefully removing the fat from the anterior
interventricular sulcus. Note the branches of the artery
to both ventricles and to the interventricular septum
which lies deep to it. Trace the artery inferiorly to the
diaphragmatic sudace and superiorly to the left of the
pulmonary trunk.The heart is supplied by two coronary arteries, arising
from the ascending aorta. Both arteries run in the
coronary sulcus.
DISSECIION
Carefully remove the fat from the coronary sulcus.
ldentify the right coronary artery in the depth of the right
part of the atrioventricular sulcus.
Trace the right coronary artery superiorly to its
origin from the right aortic sinus and inferiorly till it turns
onto the posterior surface of the heart to lie in its
atrioventricular sulcus. lt gives off the posterior inter-
ventricular branch which is seen in posterior inter-
ventriculal groove.
The right coronary aftery ends by anastomosing with
the circumflex branch of left coronary artery or by
dipping itself deep in the myocardium there.Position
Right coronary artery is smaller than the left coronary
artery. It arises from the anterior aortic sinus
(Figs 18.22a and b) of ascending aorta.