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The left atrium and the base of the heart can best be identified from a posterior view List the four heart chambers and label them in the diagram 2 3 4 D The great blood vessels are attached to the heart at the base You can identify these structures from a posterior view Identify the aortic arch passing posteriorly over the pulmonary trunk The left and right pulmonary arteries are branches of the pulmonary trunk Observe the four pulmonary veins-two on each side-as they enter the left atrium. Posterior view Word Origins Auricle is derived from auricular, the Latin word for "external ear." Early anatomists gave them that name because they resembled the external car The base of the heart is at the heart's posterior and superior aspects. identify two major sulci (grooves) on the posterior surface and label them on the diagram From the anterior surface, the coronary sulcus continues along the posterior surface between the atria and ventrides Notice that it forms a complete circle around the heart The posterior interventricular sulcus, ike the anterior interventricular sulcus, descends toward the apex from the coronary sulcus, and forms a border between the left and right ventricles Locate the superior and inferior venae cavae where they enter the right atrium MAKING CONNECTIONS From an external view, what features could you use to distinguish the right atrium from the left atrium? From an external view, what features could you use to distinguish the right ventricle from the left ventricle? EXERCISE 21 Gas Anatomy of the Heart 377