Final answer:
The broad flat part of the heart pointing toward the right shoulder is known as the base of the heart, which is centrally located in the thoracic cavity.
Step-by-step explanation:
The broad flat part of the heart that points toward the right shoulder is known as the base of the heart. The base is opposite to the apex, which lies just to the left of the sternum. While most people tend to think the heart is located on the left side of the chest, it is actually positioned more centrally in the thoracic cavity, resting between the lungs in the space called the mediastinum. The surface features of the heart, such as the auricles and various sulci, are significant as they provide pathways for blood vessels and help to demarcate the heart's chambers and valves.