The heart is a remarkable organ, an engine that runs perpetually from before we are born until our final moment. Even during growth, the heart never stops. During anatomy, exploring the body was an intimate experience which allowed me to connect with my classmates and cadaver. The dissection of the heart was memorable. Below are some sketches from the session.
The heart is a hollow tube with four chambers: two atria and two ventricles. These chambers are arranged in a pyramid, the base positioned superiorly. This post focuses on the right atrium. The right atrium receives blood from three sources: the superior vena cava, inferior vena cava, and the coronary veins. Both the superior and inferior vena cava transport blood from the body; the coronary veins drain the heart.
Inside the right atrium, one finds the anterior wall covered in grooves, termed pectinate muscles. These muscles add rigidity and facilitate the contraction of the atria during the cardiac cycle. The posterior wall is smooth, named the sinus venarum. There are three valves for the three sources of blood: superior (A), inferior (B) vena cava, and the coronary sinus (C). The depression toward the center is called the oval fossa (D). The oval fossa is named the oval foramen before birth, and used to channel blood from the right atrium to the left atrium during prenatal development. Pressure differences between the right and left atrium change when a newborn breathes for the first time, forcing the oval foramen to close. Blood flows from the right atrium into the right ventricle by way of the right atrioventricular orifice (E).
Dissecting out the heart was no easy task. The heart rests in the chest cavity behind the sternum, and covered in a tough, fibrous lining, the pericardium. Removing the heart required carefully disconnecting the arteries and veins. The right atrium was opened by cutting through the muscular, anterior wall starting from the top, cutting down and horizontal, creating a flap, as seen in the sketch.
The most spectacular feature of the right atrium is the oval foramen. The depression is no bigger than a thumbprint, but represents an old window between the two atria. The oval foramen is a remnant of the heart’s embryology, and a visual reminder of how the heart functions prenatally. Every heart has a oval foramen, and to see one in person was a special oppurtunity.
P.S. This is the first article of a series on the heart dissection. Stay tuned!