Prelab Images - Heart

Prelab should consist of reading the lab manual and dissector answers and viewing the dissection video. To begin your study, you may find it useful to look over the Netter's or LWW Atlas images listed below.

Step 1. Remove the heart from the pericardial cavity and examine its features. (Play movie)

Looking at plate N212 or TG4-19, place your finger in the transverse sinus and lift up with it so you can cut through the aorta and pulmonary trunk. Plate N206 or TG4-20 shows the superior and inferior vena cava severed at the point where they enter the right atrium, which you need to do next. Then, plate N215 or TG4-20 (top) shows the heart being pulled forward to reveal the left pulmonary veins when you look into the oblique sinus. Cut through the left pulmonary veins and then do the same on the right side for the two right pulmonary veins. Plate N215 (top and bottom) or TG4-19 shows the pericardium running on the great vessels and reflecting. Plate N241 or TG4-19 shows the visceral pericardium to be continuous with the parietal pericardium as well. Plate N216 (top) or TG4-21 is a view of the heart the way it sits in the body to help orient you once you remove the heart.

Step 2. Remove the epicardium and identify the coronary blood vessels. Play movie)

Plates N212 or TG4-19 and N215 or TG4-21 (top) show the heart encased in epicardium (visceral serous pericardium) and epicardial fat. You need to etch your way through this fat to trace the vessels of the heart. Looking at plate N216 (top) or TG4-22, start near the remaining stump of the aorta and try to find the right coronary artery in the coronary sulcus (this sulcus is labeled in N212 or TG4-21). Do not damage the small veins that cross this artery superficially (anterior cardiac- N216 top picture or TG4-24). The artery to the sinoatrial node (N216 top or TG4-23) usually branches off the right coronary artery early (it can come from the circumflex branch of the left coronary artery, as discussed later), runs under the right auricle and moves to the SA node, which is near the junction of the superior vena cava and the right atrium (N216 or TG4-25). The SA node is shown in plate N225 (top) or TG4-28. Plate N216 or TG4-22 shows the right coronary artery giving off a right marginal branch. The right coronary artery also gives off the posterior interventricular branch (N216 bottom or TG4-22), which runs in the posterior interventricular sulcus (labeled in plate N214 or TG4-21 bottom and N215 top). The posterior interventricular artery can be seen to give off interventricular septal branches (plate N216 bottom or TG4-22). The right coronary artery also gives off atrial branches (one is labeled in N216 top or TG4-22) and ventricular branches to the right ventricle (shown, but not labeled in N216 top or TG4-22). Plate N216 or TG4-24 also shows the small cardiac veins accompanying the right coronary artery. Plate N218 or TG4-23 reviews the right coronary artery and its branches. Next, find the left coronary artery (N216 or TG4-22). This branches into the anterior interventricular artery (N216 or TG4-22) that runs in the interventricular sulcus (N212 or TG4-21) and the circumflex branch (N216 or TG4-22). Plate N216 or TG4-24A and TG4-24B shows the great cardiac vein accompanying the anterior interventricular artery and it shows the anterior interventricular artery giving off interventricular septal branches. Plate N216 or TG4-22 shows the circumflex branch traced and the left marginal artery (which is a branch of the circumflex or anterior interventricular arteries). Plate N216 or TG4-22 shows, but does not label, branches of the circumflex artery to the left atrium. The circumflex artery will run under the coronary sinus (N216 bottom or TG4-22) and may anastomose with the right coronary artery. The artery to the AV node is usually a branch of the right coronary artery and usually branches off of it near the same spot the posterior interventricular branch branches off. Plate N222 or TG4-24 shows this artery diving deep into the heart. The AV node is shown in plate N225 or TG4-28. Plate N219 or TG4-23A and TG4-23B reviews the branches of the left coronary artery. Also, see plateTG4-23, and TG4-23 for some variations to the blood supply of the heart. Now organize the venous drainage of the heart. Plate N216 or TG4-24 shows the great cardiac vein as it runs around to the back of the heart and receives the posterior vein of the left ventricle before becoming the coronary sinus. Plate N216 or TG4-24 also shows the small cardiac vein as it moves to the back of the heart and empties into the coronary sinus. The middle cardiac vein is also shown to empty into the coronary sinus (N216 or TG4-22). The coronary sinus then empties all this blood into the right atrium (N220 top or TG4-24D and TG4-24C). However, the anterior cardiac veins (N216 top or TG4-24B) do not send blood to the coronary sinus, they send it straight into the right atrium.

Step 3. Open the chambers of the heart as shown in Figure 6. (Play movie), and Step 4. Clean out the chambers and identify their anatomical features. (Play movie)

First, make cut 1 that is shown in figure 6 (from the superior to the inferior vena cava). You should now have a view similar to plate N220 (top) or TG4-25. The endocardium is the lining of the heart (not labeled). Plate N220 or TG4-25 labels the following: auricle of the right atrium, openings of superior and inferior vena cavae, valve of inferior vena cava, the opening and valve of the coronary sinus, the crista terminalis (this is a ridge that marks the transition of pectinate muscle to the sinus venarum, which is the thin-walled posterior part of the right atrium), pectinate muscle, and the fossa ovalis with its limbus on the interatrial septal wall. Plate N214 or TG4-21 labels the sulcus terminalis (external feature of the heart) that relates to the crista terminalis (internal feature of the heart). Check to see if the fossa ovalis is patent (opens into the left atrium) and examine the right tricuspid valve and its cusps. Then, make cut 2 (see figure 6 of lab manual) from just below the inferior vena cava towards the interventricular septum and then up towards the pulmonary trunk. This will give you a view like plate N220 (bottom) or TG4-25 except you will pull a flap of the heart upwards instead of downwards like in this picture. Notice the myocardium (muscle of the ventricular wall). Plate N220 or TG4-25 labels the following: trabeculae carneae, papillary muscle (anterior, posterior, and septal), chordae tendineae, the tricuspid valve (anterior, posterior, and septal cusps), the septomarginal trabecula (moderator band), conus arteriosus, and the pulmonary valve with its cusps. After identifying these structures make cut 3 (see figure 6 of lab manual). Starting behind the aorta and pulmonary trunk make a cut laterally and then curve inferiorly until you are near the mitral valve. Then, cut straight laterally and around the left atrium to open the atrium up. You should now have a flap that you can pull superiorly. Plate N221 or TG4-26 shows the four pulmonary veins (2 left, 2 right) emptying into the left atrium. Plate N221 or TG4-26 shows the valve of the foramen ovale on the interatrial septum and the auricle of the left atrium. Examine the mitral valve and its anterior and posterior cusps from the left atrium (plate N221 top or TG4-26). You will see the mitral valve better after you open the left ventricle. Finally, make cut 4 (figure 6 of lab manual) by starting at the apex of the heart and cutting up towards the coronary sinus. You can now peel back the anterior wall of the left ventricle (like plate N221 top or TG4-26). Plate N221 or TG4-26 shows the trabeculae carneae of the left ventricle, but they are not labeled. The aortic vestibule is not labeled, but it is the area right before the aortic valve (analogous to the conus arteriosus of the right ventricle). Plate N221 or TG4-26 labels the following: interventricular septum (muscular and membranous parts), anterior and posterior papillary muscles with chordae tendineae attaching to the cusps of the mitral valve, and the aortic valve with its semilunar cusps. Plate N224 or TG4-27 shows how the coronary arteries open up right from the left and right cusps of the aortic semilunar valve. Plates N222, N223, and N224 or TG4-25 and TG4-27 may be helpful to review the heart valves. Plates N224, N212 or TG4-14, and objective 5 consider listening to heart sounds with a stethoscope. Next, make a cut along the left (obtuse) border of the heart from the apex through the coronary sulcus, mitral valve, and muscle of the left atrial wall. This will allow you to open the heart on the left side and look down at the fibrous ring around the mitral valve (like in plate N222). Each of the valves in plate N222 has a fibrous ring (anulus fibrosus) around it and these rings make up the fibrous skeleton of the heart. The fibrous skeleton in plate N222 prevents electrical impulses from being passed from atria to ventricles without going through the AV node (plate N225 or TG4-28). This allows the heart to coordinate heart contraction.

Updated: 30 Sep 2011