Pericardium and Heart Wall Layers

Pericardium

• The pericardium is a fluid-filled sac that surrounds the heart.
• It's a double-layered sac made of elastic connective tissue.
• The fibrous pericardium is the outermost layer.
• The serous pericardium is the inner layer, divided into parietal and visceral layers.
• The parietal layer lines the fibrous pericardium.
• The visceral layer is also called the epicardium.
• The pericardial space is between the visceral and parietal layers.
• It contains fluid (10-50 mL) to lubricate the heart during contraction and relaxation.
• Excess fluid is called pericardial effusion.

Heart Wall Layers

• The heart wall has three layers: epicardium, myocardium, and endocardium.
  • The epicardium (aka visceral pericardium) is the outermost layer.
  • It covers the heart surface and great vessels.
  • The myocardium is the middle layer, made of thick muscular tissue.
    • It's composed of striated muscle fibers and myofibrils.
    • It's the heart's main pumping mechanism.
  • The endocardium is the innermost layer, lining the chambers and valves.
    • It's a thin layer of endothelium and connective tissue.

Heart Chambers

• The heart has four chambers: two atria (right and left) and two ventricles (right and left).
• The atria are the receiving chambers.
• The right atrium receives deoxygenated blood from the body.
• The left atrium receives oxygenated blood from the lungs.
• The ventricles are the pumping chambers.
• The right ventricle pumps deoxygenated blood to the lungs.
• The left ventricle pumps oxygenated blood to the body.
• The interatrial septum divides the right and left atria.
• The right and left ventricles are separated by interventricular septum.
• The atria and ventricles have appendages (right/left atrial appendage or auricle) which help increase blood flow.

Great Vessels

• Great vessels connect to the superior part of the ventricles.
  • They carry blood away from the heart.
• Two major arteries:
  • The aorta carries oxygenated blood from the left ventricle to the body.
  • Main pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
• Six other great vessels:
  • Superior vena cava (SVC) returns deoxygenated blood from the upper body to the right atrium.
  • Inferior vena cava (IVC) returns deoxygenated blood from the lower body to the right atrium.
  • Four pulmonary veins return oxygenated blood from the lungs to the left atrium.

Cardiac Valves

• Valves ensure one-way blood flow.
• Categorized by location:
  • Semilunar valves (SL):
    • Pulmonic valve
    • Aortic valve
  • Atrioventricular valves (AV):
    • Tricuspid valve
    • Mitral valve
• The AV valves are diastolic valves, opening when the ventricles are relaxing to fill.
• The SL valves are systolic valves, opening during ventricular contraction.
• Each valve has specific components (e.g., cusps, chordae tendinae, papillary muscles) to ensure proper function.