The image is from a coronary artery bypass graft anastomosis site.
Coronary artery bypass grafting is a common procedure. Interpretation of these specimens at postmortem
examination requires knowledge of the types of vessels involved.
Firstly, there are two basic types of arteries: elastic and muscular. Elastic arteries are generally larger in caliber,
and include the aorta, pulmonary artery, and the proximal branches of these arteries. During ventricular
systole, these arteries need to absorb the volume and pressure of blood being ejected from through the
semilunar valves. Abundant elastic fibers allow these arteries to distend to accommodate this volume change,
then recoil in order to propel the blood forward and maintain diastolic blood pressure. The internal mammary
arteries are the smallest caliber elastic arteries in the body.
In contrast, muscular arteries are responsible for distribution of blood and thereby oxygen to peripheral
organs. They have less elastic fibers and instead have condensed bundles of smooth muscle to aid in arterial
constriction and relaxation. Examples of this type of artery include the coronary arteries and radial artery. Veins, on the other hand, have very little elastic fibers, and have a thin media composed of predominately
In returning to our case, the native coronary artery is on the right side of the image, which shows a muscular
artery. The left side of the image shows an elastic artery. This elastic artery is the internal mammary artery,
which is commonly used in bypass grafts.