Heart Chambers: Comprehensive Clinical Anatomy

Overview

The human heart acts as a dual pump, divided into the right heart (pumping to the pulmonary circulation) and the left heart (pumping to the systemic circulation). Each side contains a receiving chamber (atrium) and a discharging chamber (ventricle).

Right Atrium

The right atrium receives deoxygenated blood from the superior vena cava (SVC), inferior vena cava (IVC), and the coronary sinus.

Sinus Venarum: The smooth-walled posterior part derived from the embryonic sinus venosus.
Pectinate Muscles: Rough muscular ridges on the anterior wall and within the right auricle.
Crista Terminalis: A vertical ridge separating the smooth and rough parts internally (sulcus terminalis externally). The SA node is located at its superior end.
Fossa Ovalis: A depression on the interatrial septum, a remnant of the fetal foramen ovale.

Right Ventricle

The right ventricle pumps blood through the pulmonary valve into the pulmonary trunk.

Trabeculae Carneae: Irregular muscular elevations on the internal surface.
Papillary Muscles: Usually three (anterior, posterior, septal) that attach to the tricuspid valve cusps via chordae tendineae to prevent prolapse during systole.
Moderator Band (Septomarginal Trabecula): A muscular band connecting the interventricular septum to the anterior papillary muscle, carrying the right bundle branch of the conduction system.
Conus Arteriosus (Infundibulum): The smooth superior funnel leading to the pulmonary valve.

Left Atrium

The left atrium receives oxygenated blood from the four pulmonary veins.

Mostly smooth-walled, with pectinate muscles restricted to the left auricle.
Forms the base of the heart and lies directly anterior to the esophagus (enlargement can cause dysphagia).
Blood passes into the left ventricle through the mitral (bicuspid) valve.

Left Ventricle

The left ventricle forms the apex of the heart and does the heaviest work, pumping blood to the entire body at systemic pressures.

Wall Thickness: 2-3 times thicker than the right ventricle.
Papillary Muscles: Only two large ones (anterior and posterior) attaching to the mitral valve.
Aortic Vestibule: The smooth, non-muscular outflow tract leading to the aortic valve.

Clinical Relevance

Atrial Septal Defect (ASD): Often occurs at the fossa ovalis, allowing left-to-right shunting.
Ventricular Septal Defect (VSD): Most common congenital heart defect, typically in the membranous part of the interventricular septum.
Left Atrial Enlargement: Can compress the esophagus (dysphagia) or the left recurrent laryngeal nerve (hoarseness, known as Ortner's syndrome).
Myocardial Infarction: Frequently affects the thicker left ventricular wall, supplied primarily by the LAD (Left Anterior Descending) artery.

Study Points

Contrast the smooth and rough parts of the right atrium and their embryological origins.
Identify the structural differences between the right and left ventricles and relate them to physiological pressures.
Understand the clinical consequences of septal defects and chamber enlargements.