The right ventricle is a thin-walled chamber that receives deoxygenated blood from the right atrium and pumps it into the pulmonary trunk for circulation to the lungs. It forms the majority of the anterior (sternocostal) surface of the heart.
Location and External Features
The right ventricle is located anterior and slightly to the left of the right atrium. It lies directly behind the sternum and forms the largest portion of the anterior cardiac surface. The right ventricle is separated from the left ventricle by the interventricular septum and from the right atrium by the tricuspid valve.
Shape: When viewed in cross-section, the right ventricle has a crescentic shape, wrapping around the left ventricle. This shape reflects the lower pressure system of pulmonary circulation.
Wall Thickness: 3-5 mm, approximately one-third the thickness of the left ventricular wall.
Internal Anatomy
The right ventricle is divided into two functional regions:
Inflow Tract (Sinus)
The inflow tract extends from the tricuspid valve orifice to the apex of the ventricle. Its internal features include:
Trabeculae Carneae: Irregular muscular ridges lining the ventricular wall. These are of three types:
- Ridges: Attached along their entire length
- Bridges: Attached at both ends, free in the middle
- Pillars (Papillary Muscles): Attached at one end to the ventricular wall and at the other end to chordae tendineae
Papillary Muscles: The right ventricle contains three groups:
- Anterior Papillary Muscle: Largest, arises from the anterior wall
- Posterior Papillary Muscle: Arises from the inferior wall (may be multiple)
- Septal Papillary Muscle: Smallest, arises from the interventricular septum
Chordae Tendineae: Fibrous cords that connect the papillary muscles to the tricuspid valve leaflets. They prevent valve prolapse during ventricular contraction.
Moderator Band (Septomarginal Trabecula): A distinctive muscular band that crosses the ventricular cavity from the interventricular septum to the anterior papillary muscle. It contains the right bundle branch of the conduction system and provides structural support.
Outflow Tract (Conus Arteriosus / Infundibulum)
The outflow tract is a smooth-walled, funnel-shaped region leading to the pulmonary valve. It is located superiorly and to the left of the inflow region. The conus arteriosus:
- Has smooth walls (no trabeculae carneae)
- Is separated from the inflow tract by the supraventricular crest
- Leads to the pulmonary valve at its superior end
Interventricular Septum
The medial wall of the right ventricle is formed by the interventricular septum, which separates the right and left ventricles. The septum has:
- Muscular Portion: Thick, muscular lower part
- Membranous Portion: Thin, fibrous upper part (common site for ventricular septal defects)
Dimensions and Capacity
- End-diastolic volume: Approximately 80-100 mL
- Stroke volume: Approximately 70-80 mL
- Ejection fraction: Approximately 60-70%
Function
The right ventricle pumps blood into the pulmonary circulation, a low-resistance system. Key functional characteristics:
- Generates lower pressure (25-30 mmHg systolic, 0-5 mmHg diastolic)
- Has greater compliance than the left ventricle
- Responds to increased afterload by dilating rather than hypertrophying
- Functions as a volume pump (unlike the left ventricle, which functions as a pressure pump)
Clinical Significance
Right Ventricular Hypertrophy
Thickening of the right ventricular wall secondary to pulmonary hypertension, pulmonic stenosis, or left heart failure. Can be detected on ECG (right axis deviation, tall R waves in V1).
Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)
A genetic condition where right ventricular myocardium is progressively replaced by fibrofatty tissue. Leads to ventricular arrhythmias and increased risk of sudden cardiac death, particularly in young athletes.
Right Ventricular Infarction
Occurs in approximately 30% of inferior myocardial infarctions. Presents with hypotension, elevated jugular venous pressure, and clear lungs. Managed with volume resuscitation and avoidance of vasodilators.
Ventricular Septal Defect (VSD)
A congenital defect in the interventricular septum. The membranous septum is most commonly affected. Small defects may close spontaneously; large defects require surgical repair to prevent heart failure and pulmonary hypertension.