Photo 2: Gross features of the anterior heart in situ

Remove the heart (with epicardium) from the remainder of the pericardium

Find these structures:

• • Epicardium

  • Left atrium

    • Left auricle

  • Coronary (atrioventricular) sulcus

  • Diaphragmatic (inferior) surface

  • Posterior interventricular sulcus

  • Base of heart

2. Reflect anterior portions of the pericardium and thymic gland/fat to view the external heart.

Photo 3. Heart in the pericardium, thymic fat reflected

3. Using scissors, transect the superior and inferior vena cavae within 2 cm of the heart

Photo 4. Incisions of superior & inferior vena cavae

4. Pass a finger or a blunt instrument through the transverse pericardial sinus, and gently pull the ascending aorta and pulmonary trunk anteriorly. Using scissors, carefully transect the ascending aorta and pulmonary trunk about midway between the heart and the bifurcation of the pulmonary trunk.

Photo 5. Incisions of the ascending aorta & pulmonary trunk (finger in transverse pericardial sinus)

5. Locate the oblique sinus and the pulmonary veins at the base of the heart. Cradle the heart from the oblique pericardial sinus, and with slight tension, sever the pulmonary vv. with scissors. Once the pulmonary vv. are severed, remove the heart from the pericardium.

Photo 6. Oblique pericardial sinus

Photo 7. Pericardial cavity, heart removed

6. Examine the heart before further dissection. Locate the epicardium and features of the external, posteroinferior heart: L. atrium, L. auricle, coronary sulcus, diaphragmatic surface, posterior interventricular sulcus, and base of heart.

Note: The epicardium is the visceral layer of serous pericardium. It can be very difficult to separate from the deep epicardial fat. The epicardium and epicardial fat will be removed later in this dissection.

Photo 8. Epicardium

Photo 9. Diaphragmatic surface of the heart

Remove the epicardium (visceral serous pericardium), and locate coronary vasculature

Find these structures:

• • Epicardial fat

  • Right coronary a. (RCA)

    • Sinu-atrial (SA) nodal br. [possibly a branch of circumflex br.]

    • Atrioventricular (AV) nodal br. [possibly a branch of circumflex br.]

    • Right marginal br.

    • Posterior interventricular br. [possibly a branch of circumflex br.]

  • Left coronary a. (LCA)

    • Anterior interventricular br.

    • Circumflex br.

      • Left marginal a.

  • Coronary sinus

    • Great cardiac v.

    • Middle cardiac v.

    • Small cardiac vv.

  • Anterior cardiac vv.

Note: The epicardial fat is varied in amount and distribution, but tends to concentrate in the coronary sulcus, anterior and posterior interventricular sulci, and around the origins of the great vessels. Arteries located within the sulci are often visible, and can help in locating these sulci.

7. Locate the ascending aorta, and bluntly remove the epicardial fat surrounding this vessel. Be careful not to sever the origins of the R. and L. coronary aa. Also take caution to not sever the sinu-atrial nodal br. of the RCA.

Photo 10. Epicardial fat at the base of the great vessels

8. Reflect the pulmonary trunk in order to better visualize the proximal portion of the ascending aorta. Locate the origins of the R. and L. coronary aa.

Photo 11. Closeup of the external origins of the RCA & LCA

9. Locate the RCA, and clean any surrounding epicardium and epicardial fat. Follow the RCA to locate its branches: sinu-atrial (SA) nodal br., R. marginal a., atrioventicular (AV) nodal br., and posterior interventricular br.

Note: The sinu-atrial (SA) nodal br. is a branch of the RCA in 60% of individuals. In 40% of cases, it is a branch of the circumflex br. of the LCA. (Moore et al., 2014). It branches near the ascending aorta toward the SA node located near the junction of the R. atrium and superior vena cava.

Photo 12. Sinu-atrial nodal br.

Note: The RCA typically travels between the ascending aorta and the R. auricle as it enters the coronary sulcus. Use caution as you uncover the RCA at this point, as there are several (3-5) anterior cardiac vv. that travel superficially over the RCA from the R. ventricle to the R. atrium. Preserve these veins.

Photo 13. Anterior cardiac veins

Note: The R. marginal br. of the RCA is located along the inferior border of the heart and is typically the last anterior branch of the RCA.

Photo 14. R. marginal br.

Note: The AV nodal and posterior interventricular brs. arise from the RCA in 67% of individuals, and the circumflex br. of the LCA in 33% of cases (Moore et al., 2014). The AV nodal br. arises near the posterior interventricular br. and dives deep and superior toward the AV node.

Note: Heart dominance is determined by the what arteries supply the apex of the heart, and the origin of the AV nodal brs. and posterior interventricular br. Right dominance indicates that the source for the posterior interventricular br. is the RCA; left dominance is the LCA. In 18% of individuals, the posterior interventricular a. arises from both the RCA and the circumflex branch of the LCA, an arrangement known as codominance.

Photo 15. Posterior interventricular and AV nodal brs. of a right dominant heart

10. Locate the LCA, and remove any surrounding epicardium and epicardial fat. Follow the LCA, and locate its 2 main branches: anterior interventricular br. and circumflex br.

Photo 16. Anterior interventricular br. and circumflex br. of LCA

11. Locate the left marginal a., which follows the left border of the heart.

Photo 17. Branches of the circumflex br. of LCA

12. Starting in the anterior interventricular sulcus, locate the great cardiac v., and follow it back to the coronary sinus. This vein closely associates with the anterior interventricular br. of the LCA.

Photo 18. Great cardiac vein

13. Follow the coronary sinus to the diaphragmatic surface of the heart. Here you should see the confluence of the middle cardiac v. (coming from the posterior interventricular sulcus) with the coronary sinus. The middle cardiac v. is associated with the posterior interventricular br.

Photo 19. Middle cardiac vein

14. Examine the anterior surface of the heart. The small cardiac v. may be visible near the inferior border, associated with the right marginal br. The anterior cardiac vv. form bridges over the RCA (from the right ventricle to the right atrium).

Note: Recall that the anterior cardiac vv. are unique among the other cardiac veins in that they typically drain directly into the R. atrium, rather than into the coronary sinus.

Photo 20. Small cardiac vein and anterior cardiac veins

Open the chambers of the heart, and examine internal features

Find these structures:

• • Myocardium

  • Endocardium

Photo 21. Heart wall, epicardium removed

15.  Make four incisions through the heart wall as shown in the images below. If done properly, you should not sever any of the vasculature of the heart. Once complete, use forceps to remove coagulations of blood. You may rinse the chambers clean to best visualize the fine features of each chamber.  

16. Incision One: R. atrium:

Make a longitudinal incision, using scissors, starting at the superior vena cava and continuing inferiorly to the inferior vena cava.

Photo 22. Incision of the R. atrium

17. Incision Two: R. ventricle:

With scissors, make a longitudinal incision starting at the pulmonary trunk to the inferior border of the heart. Continue this incision laterally toward the R. atrium, above the R. marginal a., taking care to avoid the anterior cardiac vv.

Photo 23. Incision of the R. ventricle

18. Incision Three: L. atrium:

Rotate the heart such that the base of the heart is facing you. Make a longitudinal cut with scissors through the L. atrium between the openings of the pulmonary vv.

Photo 24. Incision of the L. atrium

19. Incision Four: L. ventricle:

With scissors, make a vertical cut through the L. ventricle. This incision should be between the anterior interventricular br. and the L. marginal a. The myocardium in the L. ventricle is thick in comparison to the other chambers.

Photo 25. Incision of the L. ventricle

Locate structures in the right atrium

Find these structures:

• • Right auricle

  • Pectinate mm.

  • Opening of coronary sinus

  • Opening of superior vena cava

  • Opening of inferior vena cava

  • Fossa ovalis (foramen ovale remnant)

Photo 26: R. atrium and auricle

Note: The smooth-walled sinus of the venae cavae is located internally between the openings of the superior and inferior venae cavae.

Note: The opening of the coronary sinus is located between the opening of the inferior vena cava and the atrioventricular (AV) orifice. If having trouble locating this opening, locate the coronary sinus externally, and follow it into the R. atrium.

Note: The fossa ovalis (a remnant of the foramen ovale) can be identified as a depression in the interatrial septum, which separates the R. and L. atria.

Photo 27: R. atrium, internal anterolateral

Note: Pectinate mm. are unique to the atria. For the R. atrium, the pectinate mm. compose the internal portions of the anterior wall.

Photo 28: R. atrium, internal posterolateral

Locate structures of the right ventricle

Find these structures:

• • Right atrioventricular (tricuspid) valve

  • Chordae tendineae

  • Papillary mm.

  • Trabeculae carneae

  • Septomarginal trabecula (moderator band)

  • Pulmonary valve

20. Locate the R. atrioventricular (tricuspid) valve. The cusps of the valve (anterior, posterior, and septal) can be identified by either looking internally into the R. ventricle or R. atrium.

Photo 29: R. atrium, internal right lateral

Note: The chordae tendineae are attached to the cusps of the atrioventricular valve. These cords originate from the apices of cylindrical papillary mm., which attach to the ventricular walls. Papillary mm. are unique to the ventricles. The R. ventricle has three papillary mm.: anterior, posterior, and septal.

Photo 30: Right ventricle, internal anterior

Note: Trabeculae carneae (“meaty beams”) compose the majority of the internal walls and are unique to the ventricles.

Note: The septomarginal trabecula (moderator band) is a specialized bundle of trabecular muscle that is located between the base of the anterior papillary m. and the inferior portion of the interventricular septum. A portion of the R. atrioventricular bundle is carried within this muscle.

Photo 31: Right ventricle, internal anterior

21. Identify the pulmonary valve by looking superiorly into the cut pulmonary trunk. There are three semilunar cusps: right, left, and anterior.

Photo 32: Heart, superior

Locate structures of the left atrium

Find these structures:

• • Left auricle

  • Pectinate mm.

  • Openings of pulmonary vv.

  • Fossa ovalis 

Note: The interior of the L. atrium is almost entirely smooth. The pectinate mm. are located only in the auricular region.

Photo 33: Left atrium, internal posterior

Photo 34: Heart, left posterolateral

Locate structures within the left ventricle

Find these structures:

• • Left atrioventricular (bicuspid) valve

  • Chordae tendineae

  • Papillary mm.

  • Trabeculae carneae

  • Aortic valve

    • Right cusp

    • Left cusp

    • Posterior semilunar (noncoronary) cusp

  • Ascending aorta

    • Aortic sinuses (of Valsalva)

22. Locate the L. atrioventricular (bicuspid) valve. This can be identified by either looking internally into the L. atrium or ventricle. This valve is composed of two cusps: anterior and posterior.

Photo 35: Left atrium, internal posterior

Note: There are only 2 papillary mm. in the L. ventricle (anterior and posterior).

Photo 36. Left ventricle, internal left superolateral

Note: The aortic valve is best viewed from a superior view. There are three semilunar (i.e. coronary) cusps: right, left, and posterior (noncoronary).

Note: The aortic sinuses (of Valsalva) are the spaces distal (superior) to the semilunar cusps of the aortic valve and proximal to the sinotubular ridge. The RCA and the LCA originate in the upper portions of the right and left aortic sinuses, respectively.

Photo 37. Aortic valve, superior

Photo 38. Aortic valve & ascending aorta, superior

23. Remove the parietal pleurae and connective tissues from the great vessels and features of the superior and middle mediastina. As you clean the aortic arch and thoracic aorta, observe the cardiac plexus in the concavity of the aorta.

Photo 39. Cardiac plexus