Chambers of the Heart
Right Atrium
The superior vena cava, inferior vena cava, and coronary sinus deposit deoxygenated blood to the right atrium from the head and neck, the rest of the body, and the heart respectively.
The blood is then pushed through the right atrioventricular valve (tricuspid) into the right ventricle.
Pectinate muscles are found on the anterolateral surface of the right atrium.
Crista terminalis is a ridge of smooth cardiac muscle on the lateral walls of the right atrium.
Presence of fossa ovalis on the interatrial septum.
Left Atrium
Four pulmonary veins deposit oxygenated blood into the left atrium.
The blood is then pushed through the left atrioventricular valve (bicuspid) into the left ventricle.
Pectinate muscles are found on the anterolateral surface of the left atrium.
Right Ventricle
The right ventricle receives deoxygenated blood from the right atrium.
The blood is pumped into the pulmonary artery through the pulmonary valve.
Trabeculae carnae are irregular muscular columns which project from the inner surface of the right ventricle. They can be further categorized as:
Papillary muscles which attach to the cusps of the atrioventricular valves. The apices of the papillary muscles are attached to chorda tendinae which are cords attached to the tricuspid valve. The contraction of the papillary muscles pull on chorda tendinae to prevent the prolapse of the tricuspid valve.
Moderator band which runs from the base of the anterior papillary muscle to the ventricular septum and plays a part in the conducting system of the heart.
Left Ventricle
The left ventricle recieves oxygenated blood from the left atrium.
The blood is pumped into the aorta through the aortic valve.
Tarbeculae carnae are irregular muscular columns which project from the inner surface of the left ventricle. They can be further categorized as:
Papillary muscles which attach to the cusps of the atrioventricular valve. The apices of the papillary muscles are attached to chorda tendinae which are cords attached to the mitral valve. The contraction of the papillary muscles pull on chorda tendiae to prevent the prolapse of the mitral valve.
Intraatrial Septum
This is the wall that separates the right atrium from the left atrium. In adult hearts, this is marked by fossa ovalis which is a remnant of the foramen ovale during fetal development.
Intraventricular Septum
This is the wall that separates the right ventricle from the left ventricle.
Summary of Blood Flow Through the Heart Chambers
The right side of the heart is formed by the right atrium, with the superior and interior venae cavae returning deoxygenated blood to the right atrium from the head, neck and arms, and the lower body, respectively.
The right atrioventricular (tricuspid) valve separates the right atrium from the right ventricle, blood flows through this valve as it exits the right atrium and enters the right ventricle. Blood leaves the right ventricle superiorly, going through the pulmonary valve and flows into the pulmonary circulation through the pulmonary trunk which splits into right and left pulmonary arteries after a short course; they supply the corresponding lungs.
After gaseous exchange in the lungs, oxygenated blood returns from the lungs via the four pulmonary veins to the left atrium situated on the posterior side of the heart. Internally, the left and right atria are separated by the atrial septum. Blood passes from the left atrium through the left atrioventricular (mitral) valve to the left ventricle which lies posterior to the right ventricle. The two ventricles are separated internally from each other by the interventricular septum. Blood leaves the left ventricle, going through the aortic valve to enter systemic circulation via the aorta which runs at first upwards and then curves backwards over the bifurcation of the pulmonary trunk.
The cusps of the valves between the atria and ventricles, and the ventricles and pulmonary trunk and aorta are arranged so that the flow of blood can only take place in the desired direction.
Borders of the Heart
The heart is usually described as:
The borders are:
Right border - formed entirely by the right atrium
Left border - formed entirely by the left ventricle
Inferior border - formed from right to left by the right atrium, right ventricle, and apex of the left ventricle
Superior border - formed from parts of the right and left atrium and the great vessels
Grooves on the external surface of the heart indicate the relative positions of the four heart chambers. The atrioventricular groove separates the atria from the ventricles and the interventricular groove separates the two ventricles.