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Heart


Atlas References

  • Netter: 216–230

  • McMinn: 185–191

  • Gray's Atlas: 92–107

Before You Begin

Inspection

Inspect the heart externally and identify the following:

  • Right atrium

  • Right auricle

  • Superior vena cava (SVC)

  • Inferior vena cava (IVC)

  • Subpulmonary infundibulum or conus

  • Pulmonary artery

  • Ascending aorta

  • Left atrium

  • Pulmonary veins

  • Left auricle ( Figs. 6.1 to 6.4 )

    Fig. 6.1, Anterior view of external surfaces of the heart; dotted outline , right auricle.

    Fig. 6.2, Topographic view of left atrium and ventricle.

    Fig. 6.3, Topographic view of the posterior heart.

    Fig. 6.4, Base, margin, and apex of topographic heart; dotted line, obtuse margin.

Identify the sulcus terminalis, a shallow groove on the surface of the right atrium, which extends between the right side of the orifice of the SVC and that of the IVC.

Dissection Tip

The dissection typically begins with the exposure and identification of the coronary arteries. Note the apex of the left ventricle and the acute (right) (see Fig. 6.1 ) and obtuse (left) (see Fig. 6.4 ) margins of the heart.

Coronary Arteries

  • o

    To remove the epicardium (visceral pericardium) and the fat covering the right coronary artery, identify the right auricle and retract it laterally.

  • o

    Palpate the space between the right auricle and the atrioventricular (AV, coronary) groove or sulcus, and expose the proximal part of the right coronary artery ( Fig. 6.5 ).

    Fig. 6.5, Topographic view of base of heart structures; dotted line, tracing of right coronary artery.

Dissection Tip

Most of the coronary arteries in adults can be felt with palpation because of their increased hardening from atherosclerotic changes of aging.

Anatomy Note

The terms atrium and auricle are not synonymous. The auricles are appendages of the atria.

  • o

    Expose the superficial portion of the right coronary artery (RCA) by cleaning away the epicardium and fat covering the vessel ( Fig. 6.6 ).

    Fig. 6.6, Dissection of right coronary artery from its origin.

  • o

    Trace the RCA toward the right side of the diaphragmatic surface of the heart, taking care to protect its branches.

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    As the artery passes near the edge of the right auricle, it usually gives off the artery of the sinu-atrial node ( Fig. 6.7 ).

    Fig. 6.7, Dissection of right coronary artery from its origin. SA, Sinu-atrial.

Anatomy Note

The sinu-atrial (SA) nodal artery arises from the proximal portion of the RCA in 65% of cases, traveling upward to the right atrium at the junction of the SVC and the right auricle, where it enters the sinu-atrial node. In the remaining cases, the SA nodal artery arises from the proximal portion of the left coronary artery.

  • o

    The second branch of the RCA is the artery of the conus, or conal artery. The conal artery arises from the proximal part of the RCA and passes to the left, around the right ventricle, at the level of the subpulmonary infundibulum (see Fig. 6.7 ). Close to the diaphragmatic surface of the heart, the RCA typically gives rise to the right marginal artery, which supplies the inferior border of the right ventricle.

  • o

    The RCA continues posteriorly in the AV (atrioventricular) groove and in most cases descends and terminates in the inferior (posterior) interventricular groove as the inferior (posterior) interventricular (descending) artery ( Fig. 6.8 ).

    Fig. 6.8, Posterior view of heart with the inferior (posterior) interventricular artery and middle cardiac vein exposed.

Anatomy Note

This artery supplies the inferior third of the interventricular septum and a portion of the inferior wall of the left ventricle.

  • o

    Before it becomes the inferior (posterior) interventricular artery, the RCA will give off the artery of the atrioventricular (AV) node.

Anatomy Note

In 80% of specimens, the AV nodal artery arises from the RCA near the inferior (posterior) interventricular groove as it crosses the “crux” of the heart ( Fig. 6.9 ). The crux of the heart is the center point of the anatomic base where the atria and ventricles are most closely approximated posteriorly.

Fig. 6.9, A, Posterior view of heart with inferior (posterior) interventricular artery and artery to the atrioventricular (AV) node exposed. B, Left atrium pulled back to reveal AV nodal artery within crux of heart.

Dissection Tip

To identify the artery to the AV node, carefully lift the left atrium at the inferior (posterior) AV groove, and clean away the fat (see Fig. 6.9B ).

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    To remove the epicardium (visceral pericardium) and the fat covering the left coronary artery, identify the left auricle and retract it laterally ( Figs. 6.10 and 6.11 ).

    Fig. 6.10, Vertical tilt of heart revealing its base and apex.

    Fig. 6.11, Superior view of the great vessels. To the left of the great vessels, fat is reflected and the origin of the left coronary artery is exposed.

  • o

    Palpate the space between the left auricle, the AV (coronary) sulcus, and expose the proximal part of the left coronary artery ( Figs. 6.12 and 6.13 ).

    Fig. 6.12, Epicardial fat is removed from the surface of the left ventricle and the anterior interventricular artery is exposed.

    Fig. 6.13, Epicardial fat removed from left ventricle with the anterior interventricular artery exposed.

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    The left coronary artery is typically very small (a few centimeters in length) and divides into the anterior interventricular coronary artery (left anterior descending) and left circumflex artery.

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    Palpate the anterior interventricular groove, and feel for the anterior interventricular artery. Use the separation technique to expose the anterior interventricular artery. This vessel gives off relatively large diagonal branches to the anterior surface of the left ventricle ( Fig. 6.14 ).

    Fig. 6.14, Removing epicardial fat from the left ventricle and exposing the anterior interventricular artery to reveal diagonal branches and a myocardial bridge.

Anatomy Note

An often-encountered variation is the presence of myocardial bridges covering the left anterior interventricular artery, which penetrates the myocardium for a few centimeters and emerges distally as an epicardial artery (see Fig. 6.14 ).

  • o

    Deeply penetrating septal branches arise from the deep surface of the anterior interventricular artery and enter the muscular interventricular septum ( Figs. 6.15 and 6.16 ) at the level of the subpulmonary infundibulum to supply the proximal parts of the left and right bundle branches.

    Fig. 6.15, Anterior interventricular artery is retracted, and septal perforating branches are exposed.

    Fig. 6.16, Left coronary artery with septal and anterior interventricular branches.

  • o

    The circumflex coronary artery runs in the left AV groove toward the left border and around to the base of the heart. This vessel typically gives off the left marginal artery crossing the left border of the heart, supplying the left ventricular free wall ( Fig. 6.17 ).

    Fig. 6.17, Lateral view with vertical tilt revealing left coronary artery, circumflex and marginal branches.

Anatomy Note

Numerous variations exist in the pattern of distribution of the right and left coronary arteries. Among the most common of the variations is the source of the inferior (posterior) interventricular coronary artery. In the majority of cases, the RCA provides the source for this artery. In about 15% of cases, however, the left circumflex artery gives off this branch.

Dissection Tip

At many times during this dissection, it is possible to identify hearts that have undergone coronary artery bypass graft (CABG) procedures ( Figs. 6.18 and 6.19 ).

Fig. 6.18, Anterior view of the heart demonstrating a great saphenous vein graft.

Fig. 6.19, Posterior view revealing the great saphenous vein graft.

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    Try to expose the graft vessel and identify to which vessel it is connected.

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    On the posterior surface of the heart at the AV sulcus between the IVC and the left atrium, identify the coronary sinus, a small confluence of veins approximately 2 cm long.

Anatomy Note

The coronary sinus receives the great cardiac vein, the middle cardiac vein, and occasionally, the small cardiac vein and the oblique vein of the left atrium.

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    Identify the great cardiac vein, which lies in the anterior interventricular groove, accompanying the left anterior interventricular artery.

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    The middle cardiac vein lies in the inferior (posterior) interventricular groove and accompanies the inferior (posterior) interventricular artery.

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    The small cardiac vein lies in the AV groove next to the opening of the coronary sinus. This vein usually joins the right marginal vein or separately opens into the right atrium.

Dissection Tip

The cardiac veins have very thin walls and are often damaged during dissection.

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