5 Right Heart Anatomy

Right Heart Anatomy refers to the study and detailed understanding of the structure, organization, and relationships of the right-sided chambers and associated components of the human heart. The right heart consists of the right atrium and right ventricle, which together receive systemic venous blood and pump it into the pulmonary circulation. The intricate arrangement of muscular, valvular, and septal elements within the right heart ensures efficient venous return, blood flow regulation, and separation of oxygen-poor blood from oxygen-rich blood within the heart.

Scope of the Right Heart Anatomy

The right heart comprises the right atrium and right ventricle, including their walls, internal structures, septal surfaces, venous inlets, and the pulmonary root. These components work collectively to guide deoxygenated blood from the systemic veins to the lungs for oxygenation.

Internal Architecture of the Right Atrium

The right atrium is a thin-walled chamber forming the right superior aspect of the heart. It is divided internally into a smooth-walled posterior part (sinus venarum) and a muscular anterior part (atrium proper), which contains the pectinate muscles arranged in parallel ridges. The two regions are separated by the crista terminalis, a crescent-shaped muscular ridge. The right atrium also presents the auricle—a muscular pouch that projects anteriorly.

Systemic Venous Openings of the Right Atrium

The right atrium receives systemic venous blood through three main orifices:

• The superior vena cava opening, located superiorly and posteriorly, brings blood from the upper body.
• The inferior vena cava opening, found inferiorly and posteriorly, includes the Eustachian (IVC) valve remnant at its margin.
• The coronary sinus, draining the myocardium, enters medially at the floor of the atrium near the septal wall and is partly guarded by the Thebesian (coronary sinus) valve.

Right Atrial Septal Surface

The medial wall of the right atrium forms the interatrial septum, which is characterized by the fossa ovalis—a shallow, oval depression. The border of the fossa is the limbus of the fossa ovalis, a prominent muscular rim. The fossa represents the closed foramen ovale of the fetal heart, which previously allowed blood to bypass the nonfunctional fetal lungs.

Right Atrioventricular Junction

The right atrioventricular junction is the region where the right atrium communicates with the right ventricle through the tricuspid orifice. This opening is guarded by the tricuspid valve, consisting of three leaflets (anterior, posterior, and septal), which prevent backflow of blood during ventricular contraction.

Internal Architecture of the Right Ventricle

The right ventricle forms most of the anterior surface of the heart and is shaped like a crescent in cross-section. Its wall is thinner than that of the left ventricle, reflecting the lower pressure required to pump blood into the pulmonary circulation. The internal surface is highly trabeculated, particularly in the inflow region.

Right Ventricular Trabecular Architecture

The right ventricular cavity features numerous muscular ridges—trabeculae carneae—which increase the surface area and prevent suction that could impede blood flow. These trabeculae are most prominent in the inflow region and are less pronounced in the outflow tract.

Right Ventricular Papillary Muscle System

Three main papillary muscles (anterior, posterior, and septal) project from the ventricular wall and attach to the tricuspid valve leaflets via chordae tendineae. These structures prevent valve prolapse during ventricular contraction by anchoring the valve leaflets.

Septomarginal and Supraventricular Muscular Structures

A key feature of the right ventricle is the septomarginal trabecula, also called the moderator band. It stretches from the interventricular septum to the anterior papillary muscle and contains the right bundle branch of the cardiac conduction system. The supraventricular crest is a muscular ridge separating the inflow and outflow regions of the ventricle.

Right Ventricular Inflow Region

The inflow portion of the right ventricle receives blood from the right atrium via the tricuspid valve. It is characterized by a rough, trabeculated surface and is directed inferiorly and anteriorly.

Right Ventricular Outflow Tract

Also known as the infundibulum or conus arteriosus, the outflow tract is a smooth-walled, funnel-shaped segment that leads to the pulmonary trunk. This region is separated from the inflow by the supraventricular crest and is essential for directing blood efficiently towards the pulmonary valve.

Pulmonary Root Junction

At the superior aspect of the right ventricle, the pulmonary root forms the origin of the pulmonary trunk. The pulmonary valve, composed of three semilunar cusps (anterior, right, and left), prevents regurgitation of blood into the ventricle after systole.

Integrated Right Heart Anatomy

The right atrium and ventricle work in tandem to receive deoxygenated blood from the systemic circulation and deliver it to the lungs. Blood enters the right atrium, passes through the tricuspid valve into the right ventricle, and is then ejected through the pulmonary valve into the pulmonary trunk. The unique muscular architecture, valve system, and spatial relationships of the right heart ensure one-way, regulated blood flow and support the overall function of the cardiovascular system.

Functional Relevance and Pressure Gradients

The right heart operates under lower pressure than the left heart. Typical systolic pressure in the right ventricle is approximately 15–30 mm Hg, and diastolic pressure is 2–8 mm Hg. This pressure gradient is crucial for the safe transfer of blood to the delicate pulmonary capillaries:

Summary

The right heart is a structurally complex and functionally specialized segment of the heart. Its chambers, valves, muscle arrangements, and septal features not only ensure the efficient flow of deoxygenated blood toward the lungs but also maintain unidirectional movement and prevent regurgitation. The right heart's architecture is fundamental to the maintenance of systemic and pulmonary circulatory separation and is essential for overall cardiovascular health.