1.1 Chambers and Valves of the heart

Surface of the heart and the corresponding chambers

  • The Heart has 5 anatomical surfaces, each formed by different chambers.

    1. Anterior surface (sternocostal):

      • Mainly formed by the right ventricle (RV)

      • Minor contribution from the right atrium (RA) and left ventricle (LV)

      • Clinical relevance: Most prone to traumatic injury; best visualised in anterior chest X-rays

    2. Right pulmonary surface:

      • Formed primarily by the right atrium (RA)

      • Lies adjacent to the right lung and pericardium

      • Important in transesophageal echocardiogram

    3. Left pulpmonary surface:

      • Formed primarily by the left ventricle (LV)

      • Contacts the left lung, helps to distinguish left heart border on the chest radiographs

    4. Interior pulmonary surface:

      • Formed by the right ventricles (RV) and left ventricles (LV)

      • Rests on the central tendon of the diaphragm

      • Clinical relevance: infarcts in this area may result from occlusion of the posterior descending artery (usually from RCA)

    5. Posterior surface (base of the heart):

      • Formed mainly by the left atrium (LA)

      • Minor contribution from the right atrium (RA)

      • Related to the esophagus and thoracic aorta

      • Clinical relevance: left atrial enlargement can compress the esophagus, affecting swallowing.

Borders of the Heart and chambers that define them

  1. Right border

    • Formed by: Right atrium

    • Clinical importance: Shifts in this border may indicate atrial enlargement.

  2. Inferior border

    • Formed by: Right ventricle and apex of the Left ventricle

    • Lies adjacent to the diaphragm; closely follows the central tendon in imaging

  3. Left border

    • Formed by: Left ventricle and left auricle

    • Represents the lateral margin of the heart on imaging

  4. Superior border

    • Formed by: Both atria (especially Left Atrium and auricle), infundibulum

    • Houses the origins of great vessels (aorta, pulmonary trunk, superior vena cava).

Cardiac skeleton, chambers and valves

Fibrous skeleton of the heart (cardiac skeleton)

  • Definition: The fibrous skeleton is a dense connective tissue framework embedded in the myocardium. It serves several essential roles

  • Structural support:

    • Provides a rigid framework that anchors the valve cusps

    • Prevent overstretching of the valve openings during the cardiac cycle

  • Electrical insulation:

    • Acts as an electrical barrier between atrial and ventricular muscle masses.

    • Ensures proper delay of impulses between atria and ventricles via the AV node

  • Components:

    • Right fibrous ring: Encircles and supports the tricuspid valve

    • Left fibrous ring: Supports the mitral (bicuspid) valve

    • Fibrous coronets: Support aortic and pulmonary valves

    • Annuli fibrosi: Four interconnected fibrous rings surrounding each valve

Heart chambers (Structure and function)

Right atrium

  • Structure:

    • Thin-walled chamber

    • Contains openings for superior vena cava, inferior vena cava, and coronary sinus

    • Includes the right auricle

  • Function:

    • Receives deoxygenated blood from the body

    • Sends blood to the right ventricle via the tricuspid valve

Right ventricle

  • Structure:

    • Forms most of the anterior surface of the heart

    • Contains trabeculae carneae, papillary muscles, and moderator band

  • Function:

    • Pumps deoxygenated blood to the lungs through the pulmonary valve into the pulmonary trunk

Left atriums

  • Structure:

    • Forms most of the posterior (base) surface

    • Receives four pulmonary veins

    • Has a small left auricle

  • Function:

    • Receives oxygenated blood from the lungs

    • Pumps it into the left ventricle via the mitral valve

Left venticle

  • Structure:

    • Thickest myocardium of all chambers

    • Contains prominent trabeculae carneae and papillary muscles

  • Function:

    • Pumps oxygenated blood into the aorta via the aortic valve

    • Supplies the entire systemic circulation

Heart valves and associated structures

Atrioventricular (AV) valves

  • Tricuspid valve:

    • Located between right atrium and right ventricle

    • Has three cusps

  • Mitral (Bicuspid) valve

    • Located between left atrium and left ventricle

    • Has two cusps

  • Cordae tendineae:

    • Fibrous cords attached to valve cusps, preventing the prolapse of valve during ventricular contraction

  • Papillary muscles:

    • Contract with ventricles

    • Pull on the cordae tendineae to maintain valve closure integrity

Semilunar valves

  • Pulmonary valve:

    • Located between right ventricle and pulmonary trunk

    • Contains 3 cusps - does not give rise to coronary arteries

      • Right cusp

      • Left cusp

      • Anterior cusp

  • Aortic valve:

    • Located between left ventricle and ascending aorta

    • Contains 3 cusps

      • Right coronary cusp — gives rise to the right coronary artery

      • Left coronary cusp — gives rise to the left coronary artery

      • Posterior (non-coronary) cusp — no coronary artery arises from the posterior cusp

  • Common features of all semilunar cusps:

    • Nodule: Thickened central area at the free edge, helping in tight closure

    • Lunule: Thin crescent-shaped edge on either side of the nodule

    • Sinuses: Small pocket-like spaces behind each cusp that help prevent cusp adherence to the vessel wall and assist in closure during diastole