Heart Anatomy: Coverings and Layers

Heart Coverings/Linings

• The visceral layer is on the organ as "guts".
• The parietal layer lines the cavity wall as a "wall".
• The visceral pericardium is also known as the epicardium.
• The visceral pericardium/epicardium has a serous layer.
• The pericardial cavity or space contains pericardial fluid.
• The parietal pericardium is a double-walled sac that surrounds the heart.
• The parietal pericardium has an inner serous layer and an outer fibrous layer.

Heart Layers

• Fibrous pericardium, serous pericardium (parietal layer), and serous pericardium (visceral layer/epicardium) are part of the pericardium.
• The space exits within these layers
• The muscle layer is called the myocardium
• The inner endothelial lining covering trabeculae is called the endocardium

Anterior Surface of the Heart

• Key components of the anterior surface of the heart include the brachiocephalic trunk, superior vena cava, right pulmonary artery, ascending aorta, pulmonary trunk, right pulmonary veins, right atrium, and right coronary artery.
• More components are the anterior cardiac vein, right ventricle, marginal artery, small cardiac vein, inferior vena cava, left common carotid artery, left subclavian artery and the aortic arch.
• The ligamentum arteriosum, left pulmonary artery, left pulmonary veins, auricle of the left atrium, circumflex artery, left coronary artery, left ventricle, great cardiac vein and the anterior interventricular artery are anterior side components.
• The apex can be seen on the anterior side.

Posterior Surface of the Heart

• Key structures on the posterior side includes the aorta, left pulmonary artery, left pulmonary veins, auricle of the left atrium, left atrium, great cardiac vein, and posterior vein of the left ventricle.
• Also observed are the left ventricle, apex, superior vena cava, right pulmonary artery, right pulmonary veins, right atrium, inferior vena cava, coronary sinus, right coronary artery found in the coronary sulcus.
• Components include the posterior interventricular artery located within the posterior interventricular sulcus, middle cardiac vein and the right ventricle during posterior view .

Heart Valves and Chambers

• Aorta, left pulmonary artery, and left atrium are found at the top
• the left pulmonary veins, right pulmonary veins, and right atrium are also located on the posterior side
• The mitral or bicuspid valve connects to the left atrium.
• The aortic valve and pulmonary valve are located near the left ventricle.
• The tricuspid valve connected to the right atrium.
• Internal structures observed are the fossa ovalis, pectinate muscles, chordae tendineae, trabeculae carneae, inferior vena cava, papillary muscle, and interventricular septum.
• Outer layers include the epicardium, myocardium, and endocardium

Atrioventricular (AV) vs Semilunar (SL) Valves

• Atrioventricular valves are located between chambers
  • Left AV valve: bicuspid (mitral) valve with 2 cusps ("LUB")
  • Right AV valve: tricuspid valve with 3 cusps
• Semilunar valves lead out of the heart
  • Pulmonary valve with 3 cusps ("DUB")
  • Aortic valve with 3 cusps

Cardiac Blood flow

• Chordae tendinae are pulled tight via the papillary muscles and closes AV valves, preventing backflow when ventricles contract.
• Papillary muscles contract and relax with the ventricles.
• Muscles allow blood to pass from the atria to the ventricles when relaxed.
• There are 3 papillary muscles in the right ventricle (tricuspid) and 2 in the left ventricle (bicuspid).

Moderator band

• The moderator band is a myocardial tissue bridge found in the right ventricle
• It carries part of the AV bundle.
• It coordinates papillary muscle contraction.

Pulmonary vs Systemic Circulation

• In pulmonary circulation, blood flows from the right ventricle to the lungs and then to the left atrium.
• The right side of the heart (ventricle) acts as the pump in this circuit.
• Deoxygenated blood becomes oxygenated during pulmonary circulation which has lower pressure.
• Vessels involved in pulmonary circulation include the pulmonary trunk, pulmonary arteries, and pulmonary veins.
• In systemic circulation, blood flows from the left ventricle to the aorta, then to the entire body, and finally back to the heart.
• The left side of the heart (ventricle) serves as the pump in this circuit.
• Arteries carry oxygenated blood, while veins carry deoxygenated blood in systemic circulation, which is a system of higher pressure.
• All blood vessels are involved,except pulmonary vessels.
• Systemic circulation ends when blood returns to the heart through the IVC and SVC.

Venous Output

• The Inferior Vena Cava (IVC), Superior Vena Cava (SVC), and Coronary Sinus all dump deoxygenated blood into the right atrium.

Sheep Heart Dissection Structures

• Key structures to identify during a sheep heart dissection include the pulmonary trunk, SVC, IVC, coronary sinus, aorta, right/left atria, and right/left ventricles.
• Also to be identified are right AV/tricuspid valve, left AV/bicuspid (mitral) valve, pulmonary and aortic semilunar valves, interventricular septum, epicardium, myocardium, endocardium, chordae tendinae, and papillary muscles.

Veins of Heart

• Anterior cardiac veins drain into the Right atrium.
• Posterior cardiac veins drain into the Coronary sinus.