Final answer:
The left lung accommodates the apex of the heart due to the presence of the cardiac notch, making it slightly smaller than the right lung.
Step-by-step explanation:
The left lung is designed to accommodate the apex of the heart. This accommodation is possible thanks to the cardiac notch, which is a depression in the medial surface of the inferior lobe of the left lung. The human heart is located medially between the lungs in the thoracic cavity, which is why the left lung is slightly smaller, possessing only two lobes compared to the three lobes of the larger right lung. This structural difference allows space for the heart within the chest cavity and is an essential aspect of gross anatomy of the lungs that is critical when observing X-rays, conducting physical examinations, or studying the physiology of the respiratory system.