The interatrial septum is the internal partition that separates the atria of the heart longitudinally. The interventricular septum on the other hand is the partition of the ventricles. Most of the anterior surface of the heart is formed mostly by the right ventricle. The left ventricle forms the apex of the heart and dominates the inferoposterior aspect of the heart. There are visible groves on the surface of the heart that clearly indicates as boundaries between its four chambers and also carry the blood vessels that supply blood to the myocardium.
The atrioventricular groove or the coronary sulcus surrounds the junction of the ventricles and the atria like a crown. The word corona literally translates to crown. In addition to supporting the anterior interventricular artery, the anterior interventricular sulcus also marks the septum that separates the ventricles into right and left parts. The anterior interventricular sulcus is the landmark of this separation while the posterior interventricular sulcus provides a similar landmark on the posteroinferior surface fo the heart.
The Receiving Chambers
When examining the heart, at first glance it may seem that the left and right atria are surprisingly free of any distinguishing surface features. However, when you examine really close, you will see that auricles or small protruding appendages exists. It is believed that the auricles increase the atrial volume. The right atrium basically has two parts. The posterior portion is characterized as having smooth walls while the anterior portion as having walls ridged by bundles of muscle tissue. The muscle tissues appear to look similar to the teeth of a comb; hence it is given the name pectinate muscles; the literal translation of pectin is comb. The crista terminalis or terminal crest is a C-shape ridge that separates the anterior and posterior regions of the right atrium. The left atrium however is undistinguished and is mostly smooth.
The fossa ovalis exists as a shallow depression found in the interatrial septum. It is the mark where the foramen ovale used to exist during the fetal stage of the heart.
The Function of the Atria
The atrium, which means entryway, functions as the chamber that receives blood that returns from the body. It only needs a fraction of energy to push the blood downward towards the ventricles, the atria has thin walls and is relatively small. They have little contribution to the propulsive pumping action of the heart.
The Discharging Chambers
Most of the volume of the heart is made up by the two ventricles. As already stated, most of the heart’s anterior surface is formed by the right ventricles. The posteroinferior surface of the heart meanwhile is dominated by the left ventricle. The trabeculae carnae marks the ventricular chambers internal walls. These trabeculae carnae or crossbars of flesh are irregular ridges of muscles. The papillary muscles, which plays a role in valve function, projects into the cavity of the ventricles.
The ventricles are the actual pump of the heart. This is the reason why when you compare the atria and the ventricles, the ventricles have much more massive walls. With the contraction of the ventricles, the blood is pushed out the heart and into the circulation. The right ventricle pumps blood towards the pulmonary trunk, which brings the pumped blood towards the lungs. Gas exchange then occurs and the blood is now oxygen rich. The left ventricles then pumps the blood towards the aorta, which is the largest artery found in the body and it then distributes the blood to the body.