The Heart

Lab Summary

This lab explores the relationships of the heart to surrounding structure and their clinical importance. Cardiac surfaces, the interior structure of the heart and coronary circulation is taught. The interior of the heart is taught through in situ and isolated dissections.

Lab Objectives

Describe the chambers of the heart that contribute to the cardiac surfaces and borders.
Describe the pericardium.
Explain the significance of the transverse pericardial sinus.
Describe the location of the major branches of the coronary arteries in relation to the atrioventricular and interventricular grooves.
Describe the position and significance of the ligamentum arteriosum and fossa ovalis.
Name the valves of the heart and the chambers / vessels they connect.
Describe the approximate location of the sinoatrial (SA) and atrioventricular (AV) nodes.
Describe the conduction system of the heart.
Describe the functional importance of papillary muscles and chordae tendineae.

Lecture List

The Heart, Exposure of the Heart, Coronary Vessels, Removal of the Heart, Bisecting the Heart, In Situ Dissection of the Heart

Anatomy of the Heart

The Heart Gallery

1.1a) Ribs show us where to listen for the valves
1.1b) Cardiac conduction system
1.1c) Cardiac conduction system
1.1d) Cardiac conduction system
1.1e) Diastole
1.1f) Systole
1.1g) Atrioventricular valves
1.1h) Aortic and pulmonary semilunar valves
1.1i) Heart viewed from the left inferior aspect
1.1j) Anterior view of right ventricle. Pulmonary valve.
1.1k) Interior of right atrium, seen from the right. Tricuspid valve.
1.1l) Interior of right atrium, seen from the right. Smooth and rough parts.
1.1m) Heart from below. Cardiac blood returns through the coronary sinus to the right atrium
1.1n) Anterior interventricular branch (LAD) runs in anterior interventricular groove
1.1o) Superior view. Pulmonary trunk, aorta, and atria removed. Valves are close together.
1.1p) Posterior inferior view. Left atrium is posterior. Ventricles sit on the diaphragm
1.1q) Anterior view. Right ventricle most of anterior surface. Right atrium – Right border. Left ventricle – Left border.

Exposure of Heart

Pericardium

Incise the pericardium in the anterior midline. Open further with transverse incisions at the apex and base.

Identify the fibrous pericardium and the parietal and visceral (epicardium) layers of the serous pericardium.

2.1a) Pericardial incisions
2.1b) Pericardium
2.1c) Visceral pericardium (epicardium)

Cardiac Surfaces

Identify the chambers of the heart, aorta, pulmonary trunk, superior and inferior vena cavae and pulmonary veins.

Lift the heart to view its diaphragmatic surface.

2.2a) Anterior heart
2.2b) Diaphragmatic surface
2.2c) Posterior surface of heart

Transverse Pericardial Sinus

Place an instrument posterior to the pulmonary trunk and ascending aorta. Note that cardiac output is anterior to the probe and the venous inflow is posterior. This space is the transverse pericardial sinus and an important landmark in cardiac surgery.

2.3a) Transverse pericardial sinus
2.3b) Transverse pericardial sinus

Left Cardiac Surface

On the left side of the heart, locate vagus nerve (X), ligamentum arteriosum and left recurrent laryngeal nerve.

The vagus nerve lies along the aortic arch. The ligamentum arteriosum connects the left pulmonary artery and the arch of the aorta. The left recurrent laryngeal artery can be identified branching from the vagus nerve and passing posterior to the ligamentum arteriosum.

L Cardiac Surface View
Labels (Top to bottom): Pulmonary trunk, ascending aorta, L ventricle, aortic arch, ligamentum arteriosum (remnant of ductus arteriosus), L atrial appendage, L pulmonary artery, L recurrent laryngeal N — 2.4a) Left heart

Right Cardiac Surface

On the right side of the heart, re-identify the hilus of the lung and find the arch of the azygos vein passing superior to the hilus of the lung to enter the superior vena cava.

Identify the atrioventricular groove on the right side of the heart. The right coronary artery lies in this groove.

R cardiac surface view
Labels (left to right): Arch of azygos vein, R mainstem bronchus, superior vena cava, ascending aorta, R pulmonary artery, R superior pulmonary vein, R ventricle, R atrium, R atrial appendage, atrioventricular groove, inferior vena cava, diaphragm — 2.5a) Right heart

Coronary Vessels

Diagram of Coronary Vessels

Identify the interventricular and atrioventricular grooves, left atrium, pulmonary veins and inferior vena cava.

Coronary arteries run in atrioventricular and interventricular grooves, which are usually fat-filled. The coronary sinus also runs in the atrioventricular groove posteriorly.

Blunt dissection of these spaces is essential.

Labels (top to bottom): Ascending aorta, marginal branches, coronary sulcus, anterior interventricular branches, marginal branches, apex, posterior interventricular branches — 3.1a) Coronary vessels

Coronary Vessels

On the anterior surface of the heart, find the right atrium and right ventricle. Locate the atrioventricular groove and expose the right coronary artery.

Elevate the heart and follow the right coronary artery to the posterior surface of the heart.

Locate the terminal branch, the posterior interventricular artery (in the interventricular groove).

Identify the coronary sinus (the main venous return) in the posterior atrioventricular groove. This may be clearer once the heart has been removed.

3.2a) Right coronary artery
3.2b) Coronary sinus
3.2c) Coronary sinus

Left Coronary Artery

Dissect posterior to the pulmonary trunk to locate the left mainstem coronary artery and follow its main branches.

Locate the anterior interventricular artery (left anterior descending – LAD) in the anterior interventricular groove.

Locate the circumflex branch passing posteriorly in the atrioventricular groove.

3.3a) Anterior interventricular artery (LAD)
3.3b) Left coronary and circumflex arteries

Removal of Heart

Removing the Heart

Divide the ascending aorta. Retract the ascending aorta inferiorly; identify the right and left pulmonary arteries. (They were previously divided at the hilus of each lung.)

Identify and transect the ligamentum arteriosum between the left pulmonary artery and the aorta.

Divide the superior vena cava above the right atrium.

On the right side of heart, divide azygos vein close to the SVC.

Divide the inferior vena cava at the level of the diaphragm.

Return the heart frequently to its in situ position in order to orient yourselves.

4.1a) Division of the aorta
4.1b) Division of the ligament arteriosum
4.1c) Inferior vena cava (may have been previously divided)
4.1d) Divisions of the azygos

Bisecting the Heart

Divide the heart into anterior and posterior segments by making a cut from the apex through the atria.

Use a long knife to make a uniform division that includes all of the chambers of the heart. This is a coronal cut tilted to include the apex and right atrium as well as the left atrial appendage.

Leave the left border of the heart intact. This procedure will allow the heart to be opened like a book.