Cardiac Anatomy: AV Valve Structure and Blood Flow Through the Heart

Cardiac Anatomy and Physiology

Collagen Cords Attached to AV Valve Flaps

The atrioventricular (AV) valves are critical structures in the heart that prevent the backflow of blood between the atria and ventricles. They are supported by specialized collagen cords.

• Chordae Tendineae: The chordae tendineae are strong, fibrous collagen cords that attach the edges of the AV valve flaps (cusps) to the papillary muscles located on the inner walls of the ventricles.

• Function: These cords prevent the valve flaps from inverting or prolapsing into the atria when the ventricles contract, ensuring one-way blood flow.

• Associated Structures: The chordae tendineae are anchored to papillary muscles, which contract to maintain tension on the cords during ventricular contraction.

• Valves Involved: The right AV valve is the tricuspid valve, and the left AV valve is the bicuspid (mitral) valve.

• Clinical Relevance: Damage to the chordae tendineae or papillary muscles can result in valve regurgitation and impaired cardiac function.

Example: During ventricular systole, the papillary muscles contract, pulling on the chordae tendineae and preventing the AV valve cusps from everting into the atria.

Blood Flow Through the Heart

The heart is a double pump that circulates blood through two main circuits: the pulmonary and systemic circuits. Understanding the pathway of blood through the heart is essential for comprehending cardiovascular physiology.

• Step 1: Blood enters the right atrium from the superior vena cava, inferior vena cava, and coronary sinus.

• Step 2: Blood flows through the tricuspid valve (right AV valve) into the right ventricle.

• Step 3: The right ventricle contracts, sending blood through the pulmonary semilunar valve into the pulmonary trunk and then into the pulmonary arteries.

• Step 4: Blood travels to the lungs, where it is oxygenated.

• Step 5: Oxygenated blood returns to the left atrium via the pulmonary veins.

• Step 6: Blood passes through the bicuspid (mitral) valve (left AV valve) into the left ventricle.

• Step 7: The left ventricle contracts, forcing blood through the aortic semilunar valve into the aorta.

• Step 8: Blood is distributed from the aorta to the systemic circulation, supplying oxygen and nutrients to body tissues.

Summary Table: Blood Flow Through the Heart

Chamber/Structure	Valve	Direction of Blood Flow
Right Atrium	Tricuspid Valve	To Right Ventricle
Right Ventricle	Pulmonary Semilunar Valve	To Pulmonary Trunk/Arteries
Left Atrium	Bicuspid (Mitral) Valve	To Left Ventricle
Left Ventricle	Aortic Semilunar Valve	To Aorta

Example: If a patient has a blockage in the pulmonary artery, blood flow from the right ventricle to the lungs is impeded, leading to decreased oxygenation of blood.

Additional info: The heart valves ensure unidirectional flow and prevent backflow. The sequence of blood flow is essential for efficient oxygenation and nutrient delivery throughout the body.