Interior of chambers of heart - Longitudinal axis section
In this specimen, we can see the interiors of Right atrium separated from Left atrium by the Inter- atrial septum. The Right ventricle is separated from left ventricle by the [Inter- ventricular septum] (#ref-6). The right and left atria opens into the right and left ventricles respectively via the atrioventricular orifices. The right atrioventricular orifice is guarded by the tricuspid valve while the left atrioventricular orifice is guarded by the bicuspid valve. We can see anterior papillary muscle here in the right ventricle. We can also identify the papillary muscles inside the left ventricle connected to the cusp of bicuspid valve by chordae tendinae. The Superior vena cava can be seen draining into right atrium which brings blood from upper half of the body. The pulmonary trunk is also seen. The difference in the thickness of walls between the left and right ventricles is also observed in this specimen. The wall of the left ventricle is three times thicker than that of the right ventricle.
Interior of Right atrium:
It is divided into three parts. Smooth part or sinus venarum, rough anterior part or pectinate part including the auricle and the interatrial septum. The superior and inferior vena cavae along with the coronary sinus opens into the smooth part. The rough anterior part presents a series of transverse muscular ridges called Musculi pectinate. The muscular ridges arise from the crista terminalis. In the auricle the muscle are interconnected to form a network. Interatrial septum (described separately)
Interior of Left atrium:
The anterior wall of the left atrium is formed by the interatrial septum while the posterior surface forms the anterior wall of the oblique sinus. The septal wall shows the fossa lunata corresponding to the fossa ovalis of the right atrium
It presents a shallow depression called the fossa ovalis (in embryonic life- septum primum). The prominent margin of the fossa ovalis is formed by the limbus fossa ovalis (in embryonic life- septum secundum).
Interior of Right ventricle:
The interior of the right ventricle has two parts: The rough inflowing part called the trabeculae carneae and the smooth outflowing part called the infundibulum. The infundibulum gives rise to the pulmonary trunk. The trabeculae carneae are muscular ridges and are of three types: ridges (fixed elevation), bridges and papillary muscles. The most prominent ridge is the supraventicular crest. The septomarginal trabecula or the moderator band is a prominent bridge extending from the ventricular septum to the base of the anterior papillary muscle. The papillary muscles or pillars are three: anterior, posterior and septal. These pillars provide thread like projection called the chordae tendinae that are attached to the cusps of the atrioventricular valves.
Interior of Left ventricle:
It contains the trabeculae carneae and the smooth outflowing part called the aortic vestibule. The anterior and posterior papillary muscles are well developed. The aortic vestibule continues as the ascending aorta.
Its upper part is thin and separates the right and left ventricles and also the right atrium from the left ventricle. The lower part of the septum is thick, muscular and separates the two ventricles.
Thread like structures extending from the papillary muscles and attached to the cusps of the atrioventricular valves.
Superior vena cava:
A large vein draining the upper part of the body. It is formed by the union of the right and left brachiocephalic veins.
The pulmonary trunk carries deoxygenated from the right ventricle. It branches into right and left pulmonary arteries and conveys the blood to the lungs.