Chordae Tendineae and Auricles

• Chordae tendineae are cord-like tendons that connect the papillary muscles to the tricuspid valve and the mitral valve in the heart.
• Also known as heart strings.
• They are composed of approximately 80% collagen, with the remainder comprised of elastin and endothelial cells.
• Chordae tendineae prevent the valves from prolapsing back into the atria during ventricular contraction (systole).
• There are two types: chordae tendineae primae, which arise from the free edge of the valve leaflets, and chordae tendineae secundae, which arise from the ventricular surface of the leaflets.
• Rupture of the chordae tendineae can lead to mitral or tricuspid valve regurgitation, where blood leaks back into the atria.
• The length and thickness of the chordae tendineae contribute to the proper functioning of the heart valves.

Auricles

• Auricles, also known as atrial appendages, are small, ear-shaped pouches that protrude from the atria of the heart.
• They increase the blood-holding capacity of the atria.
• The right auricle is typically larger than the left auricle.
• Auricles are more trabeculated (ridged) than the atria themselves.
• They play a role in the production of atrial natriuretic peptide (ANP), a hormone that helps regulate blood volume and blood pressure.
• Due to their shape and location, auricles are prone to the formation of blood clots, especially in conditions like atrial fibrillation.
• Transesophageal echocardiography (TEE) is often used to visualize the auricles for the presence of thrombi (blood clots) before procedures like cardioversion.
• The left atrial appendage is often targeted for closure in patients with atrial fibrillation to reduce the risk of stroke.

Coronary Arteries

• Coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart muscle.
• The two main coronary arteries are the left coronary artery (LCA) and the right coronary artery (RCA).
• The LCA branches into the left anterior descending artery (LAD) and the left circumflex artery (LCx).
• The LAD supplies blood to the anterior wall of the left ventricle, the interventricular septum, and part of the right ventricle.
• The LCx supplies blood to the lateral and posterior walls of the left ventricle.
• The RCA supplies blood to the right atrium, the right ventricle, the posterior part of the left ventricle, and the sinoatrial (SA) and atrioventricular (AV) nodes in most individuals.
• Blockage of the coronary arteries, often due to atherosclerosis, can lead to angina (chest pain) or myocardial infarction (heart attack).
• Coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI) are common procedures used to restore blood flow to the heart muscle in cases of coronary artery disease.
• Variations in coronary artery anatomy are common, and the dominance of either the RCA or LCA in supplying the posterior descending artery (PDA) is a key factor in determining coronary circulation patterns.

Pericardium

• The pericardium is a double-layered sac that surrounds the heart and the roots of the great vessels.
• It consists of two main layers: the fibrous pericardium and the serous pericardium.
• The fibrous pericardium is the outer layer and is made of dense connective tissue, providing protection and anchoring the heart within the mediastinum.
• The serous pericardium is the inner layer and is further divided into two layers: the parietal pericardium (lining the inner surface of the fibrous pericardium) and the visceral pericardium (epicardium), which adheres directly to the heart.
• The space between the parietal and visceral layers of the serous pericardium is the pericardial cavity, which contains a small amount of serous fluid that lubricates the surfaces and reduces friction during heartbeats.
• Functions of the pericardium include: protecting the heart from infection, preventing excessive dilation of the heart, and providing lubrication to reduce friction.
• Conditions affecting the pericardium include pericarditis (inflammation of the pericardium), pericardial effusion (accumulation of fluid in the pericardial cavity), and cardiac tamponade (compression of the heart due to fluid accumulation).
• Pericardiocentesis is a procedure to remove fluid from the pericardial cavity, often performed in cases of cardiac tamponade.
• The pericardium is innervated by the phrenic nerve, which can cause referred pain to the shoulder or neck in cases of pericardial irritation.