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Heart Dissection Guide

Complete guide to cardiac anatomy through systematic dissection of the heart. Learn the chambers, valves, coronary circulation, and conduction system with clinical correlations to common cardiac pathology.

Learning Objectives

  • ✓Identify all four chambers and their internal features
  • ✓Examine all four cardiac valves and understand their function
  • ✓Trace the coronary arteries and cardiac veins
  • ✓Identify the components of the conduction system
  • ✓Correlate anatomy with common cardiac pathologies

Prerequisites

  • • Understanding of mediastinal anatomy
  • • Knowledge of great vessels
  • • Review of cardiac cycle and blood flow
  • • Familiarity with cardiac imaging (echo, angiography)

Equipment Needed

  • • Scalpel with #22 blade
  • • Dissecting scissors
  • • Forceps
  • • Probe
  • • Cardiac dissection tray
  • • Water source for flushing

Dissection Steps

Step 1:External Examination

Orient the heart with the apex pointing inferiorly and to the left. Identify the anterior (sternocostal) and posterior (diaphragmatic/base) surfaces. Locate the coronary sulcus (atrioventricular groove) and anterior/posterior interventricular sulci.

Key Structures

ApexBaseCoronary sulcusAnterior interventricular sulcusPosterior interventricular sulcusAuricles
Tip:The anterior surface is mainly right ventricle. The left ventricle forms the left border and apex. The right border is the right atrium.

Step 2:Identify Coronary Arteries

Locate the right coronary artery (RCA) arising from the right aortic sinus, running in the coronary sulcus. Find the left main coronary artery (LMCA) from the left aortic sinus, dividing into LAD and circumflex. Trace their branches.

Key Structures

Right coronary arteryLeft main coronary arteryLeft anterior descending (LAD)Circumflex arteryPosterior descending arteryMarginal branches
Tip:The LAD runs in the anterior interventricular sulcus. In 70% of people, the RCA gives off the posterior descending artery (right dominance).

Step 3:Open the Right Atrium

Make an incision from the SVC to the IVC along the right border of the heart, then extend into the right auricle. Identify the internal structures: crista terminalis, pectinate muscles, fossa ovalis, and openings of the coronary sinus, SVC, and IVC.

Key Structures

Crista terminalisPectinate musclesFossa ovalisLimbus fossa ovalisCoronary sinus openingSVC openingIVC openingEustachian valve
Tip:The SA node is located at the junction of the SVC and right atrium, near the superior end of the crista terminalis.

Step 4:Examine the Tricuspid Valve

Identify the three leaflets of the tricuspid valve: anterior, posterior, and septal. Trace the chordae tendineae to the papillary muscles (anterior, posterior, septal). Note how papillary muscles attach to leaflets from adjacent cusps.

Key Structures

Anterior leafletPosterior leafletSeptal leafletChordae tendineaeAnterior papillary musclePosterior papillary muscleSeptal papillary muscle
Tip:The septal papillary muscle is often small or absent. The moderator band connects to the anterior papillary muscle.

Step 5:Open the Right Ventricle

Make an incision parallel to the interventricular septum, from the tricuspid valve toward the apex, then up toward the pulmonary trunk. Identify the trabeculated inflow tract and smooth outflow tract (conus arteriosus). Find the moderator band.

Key Structures

Trabeculae carneaeModerator band (septomarginal trabecula)Conus arteriosus (infundibulum)Supraventricular crestPulmonary valve
Tip:The moderator band carries the right bundle branch to the anterior papillary muscle. It's a reliable landmark in the right ventricle.

Step 6:Examine the Pulmonary Valve

Identify the three semilunar cusps of the pulmonary valve: anterior, right, and left. Note the sinuses behind each cusp and the smooth infundibulum below the valve.

Key Structures

Anterior cuspRight cuspLeft cuspPulmonary sinusesInfundibulum
Tip:Unlike the aortic valve, the pulmonary valve cusps do not give rise to coronary arteries. The cusps are named by position.

Step 7:Open the Left Atrium

Make an incision between the right pulmonary veins on the posterior surface. Extend into the left auricle. Note the smooth walls (no pectinate muscles except in auricle), pulmonary vein openings, and the valve of the foramen ovale.

Key Structures

Pulmonary vein openings (4)Left auricleValve of foramen ovaleInteratrial septum
Tip:The left atrium is the most posterior chamber. The four pulmonary veins enter at the corners. Atrial fibrillation often originates near pulmonary vein ostia.

Step 8:Examine the Mitral Valve

Identify the two leaflets: anterior (aortic) and posterior (mural). Trace chordae tendineae to the two papillary muscles (anterolateral and posteromedial). Note how both papillary muscles attach to both leaflets.

Key Structures

Anterior leafletPosterior leafletAnterolateral papillary musclePosteromedial papillary muscleChordae tendineaeCommissures
Tip:The anterior leaflet is larger but the posterior leaflet has a larger circumferential attachment. Both papillary muscles receive chordae from both leaflets.

Step 9:Open the Left Ventricle

Make an incision from the mitral valve to the apex along the left border, then up toward the aortic valve. Note the thick walls (3x right ventricle), fine trabeculae, and the aortic vestibule. Identify the membranous interventricular septum.

Key Structures

Trabeculae carneaeAortic vestibuleInterventricular septum (muscular and membranous parts)Papillary musclesMitral-aortic continuity
Tip:The membranous septum is a common site for VSDs. The bundle of His passes through this area.

Step 10:Examine the Aortic Valve

Identify the three semilunar cusps and their corresponding sinuses of Valsalva. Locate the coronary artery ostia in the right and left sinuses. The posterior (non-coronary) sinus has no artery.

Key Structures

Right coronary cuspLeft coronary cuspNon-coronary (posterior) cuspSinuses of ValsalvaCoronary ostiaSinotubular junction
Tip:The coronary arteries fill during diastole when the cusps close and blood flows into the sinuses. Aortic stenosis is the most common valvular disease.

Clinical Correlations

  • •Myocardial infarction: LAD occlusion affects anterior wall and septum; RCA occlusion affects inferior wall and may involve SA/AV nodes
  • •Atrial septal defect: persistent foramen ovale or secundum defect causes left-to-right shunt
  • •Ventricular septal defect: most common at membranous septum, causes left-to-right shunt
  • •Mitral valve prolapse: leaflets prolapse into left atrium during systole
  • •Aortic stenosis: calcification of valve cusps (bicuspid valve is a risk factor)

Common Mistakes to Avoid

  • ✗Confusing the orientation (apex down and left, base up and posterior)
  • ✗Cutting through the coronary arteries when opening chambers
  • ✗Mistaking the coronary sinus for a pulmonary vein
  • ✗Confusing the tricuspid (3 leaflets, right side) with mitral (2 leaflets, left side)

Study Questions

  1. What is the blood supply to the SA and AV nodes in right-dominant circulation?
  2. Why does the left ventricle have a thicker wall than the right ventricle?
  3. What is the clinical significance of the moderator band?
  4. How does the anatomy of the mitral valve predispose to regurgitation?
  5. Why are ventricular septal defects most common in the membranous septum?

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FAQs

Common questions about this dissection

Coronary dominance refers to which artery gives off the posterior descending artery (PDA). In 70% of people, the RCA provides the PDA (right dominant). In 10%, the circumflex provides it (left dominant). In 20%, both contribute (codominant).

The left heart operates at higher pressures (systemic vs pulmonary), causing more mechanical stress on the mitral and aortic valves. This leads to earlier wear and calcification compared to the tricuspid and pulmonary valves.

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