The right ventricle is one of the four chambers of the heart, specifically one of the two lower chambers. It plays a crucial role in the circulatory system by pumping deoxygenated blood to the lungs.
Location
The right ventricle is located in the lower part of the heart, beneath the right atrium and to the right of the left ventricle (when viewed from the anterior aspect). It sits just behind the sternum (breastbone) and to the left of the vertebral column.
Structure
The structure of the right ventricle is tailored to its function of pumping blood to the lungs through the pulmonary artery. Key structural features include:
Shape and Size
The right ventricle is triangular in shape when viewed from the side and crescent-shaped in cross-section. It is thinner and less muscular than the left ventricle because it pumps blood a shorter distance (to the lungs, not throughout the entire body) and against a lower pressure.
Walls
The walls of the right ventricle are lined with trabeculae carneae, which are irregular, muscular ridges. The wall is thinner than that of the left ventricle, typically 3 to 5 mm in thickness.
Interventricular Septum
This is the thick wall separating the right ventricle from the left ventricle. The septum prevents the mixing of deoxygenated and oxygenated blood between the two ventricles.
Valves
The right ventricle has two main valves associated with it:
- Tricuspid Valve: Located between the right atrium and the right ventricle, this valve allows blood to flow from the atrium into the ventricle while preventing backflow.
- Pulmonary Valve: Situated at the entrance to the pulmonary artery, this valve allows blood to exit the right ventricle into the pulmonary artery and prevents it from flowing back into the ventricle.
Inflow and Outflow Tracts
The right ventricle has a distinct inflow tract that receives blood from the right atrium and an outflow tract (infundibulum or conus arteriosus) that leads to the pulmonary artery.
Papillary Muscles and Chordae Tendineae
These structures are part of the apparatus of the tricuspid valve. The papillary muscles attach to the valve via the chordae tendineae and contract to prevent the valve leaflets from inverting or prolapsing into the right atrium during ventricular contraction.
Development
The development of the right ventricle is a complex process that begins early in embryonic life as part of the overall development of the heart.
The heart begins to form during the third week of embryonic development from a primitive heart tube, which is initially a straight tube composed of an inner endothelial layer and an outer myocardial layer. This tube undergoes folding and partitioning to form the different chambers and structures of the heart.
Division of the Primitive Heart Tube: The primitive heart tube elongates and undergoes looping, forming a C-shaped structure. This looping brings the future atrial and ventricular segments into their correct spatial orientation.
Formation of the Ventricular Chambers: After looping, the heart tube’s distal portion (the future ventricles) expands more than the proximal portion (the future atria), setting the stage for chamber differentiation. The interventricular septum begins to develop, dividing the primitive ventricle into the left and right ventricles.
Development of the Interventricular Septum: The septum formation starts with a muscular ridge growing upwards from the floor of the ventricular chamber, dividing it into right and left parts. This process creates the muscular part of the interventricular septum. A membranous portion of the septum will form later to complete the separation between the two ventricles.
Trabeculation: The inner walls of the developing right ventricle become irregular and form muscular ridges known as trabeculae carneae. These are important for the contractile function of the heart and contribute to the characteristic appearance of the ventricular walls.
Development of the Outflow Tract: The outflow tract of the right ventricle, which will become the pulmonary trunk, originates from the truncus arteriosus, a structure that divides to form the roots of the future pulmonary artery and aorta. The division is completed by the formation of the aorticopulmonary septum, which aligns with the interventricular septum to ensure proper routing of blood flow.
Valve Formation: The tricuspid and pulmonary valves develop from endocardial cushions, which are swellings of extracellular matrix that form within the heart tube. These cushions undergo remodeling to form the leaflets and supporting structures of the valves.
By the end of the embryonic period, the right ventricle is well-defined and separated from the left ventricle, ready to take on its role in pumping deoxygenated blood to the lungs. The development of the right ventricle is critical for the overall function of the heart and the circulatory system. Errors in this development can lead to congenital heart defects affecting the right ventricle’s structure and function.
Function
The right ventricle plays several crucial roles in the cardiovascular system, primarily related to pulmonary circulation, which is the movement of blood between the heart and the lungs.
Here are the main functions of the right ventricle:
Pulmonary Circulation: The primary function of the right ventricle is to pump deoxygenated blood received from the right atrium into the lungs via the pulmonary artery. This circulation allows blood to be oxygenated and rid of carbon dioxide.
Maintaining Lower Pressure: Compared to the left ventricle, the right ventricle operates under lower pressure. This is because the pulmonary circulation system (lungs) offers less resistance than the systemic circulation. The right ventricle is structurally adapted for this function, having thinner walls and less myocardial muscle mass than the left ventricle.
Volume Pump: The right ventricle is considered a volume pump. It handles the same volume of blood as the left ventricle but at a lower pressure. It ensures that the amount of blood sent to the lungs matches the amount of blood pumped out to the body by the left ventricle, maintaining balance in the circulatory system.
Adapting to Changing Demands: The right ventricle can adapt to varying demands on the body, such as during exercise or at high altitudes. It can increase its output to meet the higher oxygen demands of the body without significantly increasing pulmonary blood pressure.
Ventilation-Perfusion Matching: Through its pumping action, the right ventricle helps to match ventilation (airflow) with perfusion (blood flow) in the lungs. This is essential for efficient gas exchange – the uptake of oxygen and the release of carbon dioxide.
Supporting Left Ventricular Function: While the right ventricle’s main role is in pulmonary circulation, its function indirectly supports the left ventricle by ensuring a continuous supply of oxygenated blood for systemic circulation. Efficient right ventricular function is necessary for maintaining the preload (initial stretching of the cardiac myocytes prior to contraction) of the left ventricle.
Responding to Hypoxic Conditions: The right ventricle plays a role in the body’s response to hypoxia (low oxygen levels). Under hypoxic conditions, the right ventricle can increase its force of contraction to maintain adequate blood flow through the lungs, where blood is oxygenated.
Clinical Significance
The right ventricle (RV) holds considerable clinical significance due to its critical role in pulmonary circulation and its impact on overall cardiovascular health.
Pulmonary Hypertension: One of the most important clinical concerns related to the right ventricle is pulmonary hypertension (PH), a condition characterized by increased pressure in the pulmonary arteries. PH can lead to right ventricular hypertrophy (enlargement) as the RV struggles to pump blood against higher resistance. Over time, this can progress to right ventricular failure, a serious condition with significant morbidity and mortality.
Right Ventricular Failure: Failure of the right ventricle can occur due to chronic pressure overload (as in PH), volume overload, myocardial infarction affecting the RV, or congenital heart diseases. Symptoms may include fatigue, swelling of the legs and abdomen, and shortness of breath. Right ventricular function is crucial for maintaining adequate cardiac output and blood flow through the lungs.
Congenital Heart Diseases: Several congenital heart defects primarily affect the right ventricle, such as Tetralogy of Fallot, tricuspid atresia, and pulmonary atresia. These conditions can significantly impact the structure and function of the RV and may require surgical intervention early in life.
Diagnostic Imaging and Biomarkers: The assessment of right ventricular size, function, and pressure is vital in diagnosing and managing various cardiac and pulmonary conditions. Techniques such as echocardiography, MRI, and the use of biomarkers like BNP (B-type natriuretic peptide) can help evaluate RV function and guide treatment decisions.
Impact on Treatment Strategies: Understanding the role and status of the right ventricle is essential in managing various cardiovascular and pulmonary conditions. For example, the management of left heart failure can be complicated by the presence of RV dysfunction, and treatments may need to be adjusted accordingly. Similarly, surgical and medical strategies for pulmonary hypertension, congenital heart defects, and other conditions often consider the impact on the right ventricle.
Prognostic Value: The function of the right ventricle is a significant prognostic factor in various heart and lung diseases. RV dysfunction is associated with increased mortality in conditions such as heart failure, pulmonary hypertension, and after major cardiac surgeries.
