Heart Anatomy: Pericardium & Heart Wall

• The heart is located in the mediastinum, within the pericardial sac.

Pericardium

• This membrane or sac surrounds the heart
• Functions include holding the heart in its position, preventing overfilling, and decreasing friction during movement.
• It consists of two layers, the fibrous pericardium, and the serous pericardium

Fibrous Pericardium

• This is the outer layer that rests on and attaches to the diaphragm
• This is a tough, inelastic, irregular connective tissue layer
• It prevents overstretching and overfilling of the heart

Serous Pericardium

• Parietal layer is attached to the inside of the fibrous pericardium
• Visceral layer is the layer of the heart wall that sticks to the surface of the heart
• Serous fluid is between the parietal and visceral layers of the serous pericardium, lubricating the heart and decreasing friction
• Pericardial effusion occurs when the pericardium becomes filled with fluid or blood

Layers of Heart

• Epicardium makes up the first layer
• Thin outer layer
• This is the visceral layer of the serous pericardium
• Myocardium is the middle layer composed of muscle
• This makes up ~95% of the heart.
• Striated like skeletal muscle but involuntary
• Endocardium makes up the inner layer
• Contains epithelial tissue with basement membrane
• This lines the chambers of the heart and the valves
• Continuous with the endothelial lining of the great vessels

Chambers

• Right Atrium exists
• Blood enters from the superior vena cava (SVC) and inferior vena cava (IVC), which carry deoxygenated blood from the body, and through the Coronary Sinus (deoxygenated blood from the myocardium)
• Walls exist
• The anterior consists of rough muscular ridges referred to as pectinate muscles
• The depression in the fetal heart is called the fossa ovale
• Outflows blood through the Tricuspid valve
• Right Ventricle exits
• Walls are rough due to the trabeculae carneae
• Outflows blood through the pulmonary semilunar valve into the pulmonary trunk
• Blood travels to the lungs via the pulmonary arteries
• Left Atrium exists
• Receives oxygenated blood via 4 pulmonary veins
• Walls are smooth
• It outflows blood through the mitral valve to the left ventricle
• Left Ventricle exists
• There is a very thick wall
• Walls have trabeculae carneae
• Outflows blood to the aorta

Atrioventricular Valves

• Tricuspid and bicuspid valves
• Allows blood flow from atria to ventricles
• Papillary muscles contract to keep valves closed

Semilunar Valves

• Pulmonic and aortic valves
• Allow blood flow to move from ventricles
• Pulmonic moves to the lungs, and Aortic moves to the myocardium
• 3 of each exist shaped like loops

Coronary Circulation

• This brings nutrition directly to the myocardium
• The heart can not use blood that is in atria or ventricles
• Found on the surface of the heart in sulci
• Coronary Arteries:
  • The right coronary artery supplies the right atrium (RA), right ventricle (RV), ¼ of left ventricle (LV), ventricular septum, SA node (60%).
  • The left coronary artery supplies the left atrium (LA), ¾ of left ventricle (LV), AV node (40%)
• Cardiac veins and the coronary sinus
  • Transports blood that has been used by the myocardium back to the right atrium (RA).

An overview of the heart location and the pericardium, including its fibrous and serous layers. Also covers the serous fluid and pericardial effusion. Briefly introduces the layers of the heart wall.