Final answer:
The apex of the lung is associated with structures such as pulmonary vessels, the hilum, pleurae, and nearby adrenal glands, playing a role in the respiratory system's function of gas exchange.
Step-by-step explanation:
The apex of the lung is the superior region that is located at the top of the lung, just beneath the ribcage and above the clavicles. Associated with the apex of the lung are various structures including the pulmonary artery, pulmonary veins, the phrenic nerve, and lymphatic vessels. One notable structure often mentioned in relation to the apex is the hilum, which is the concave region on the lung's mediastinal surface where various structures such as blood vessels, lymphatic vessels, nerves, and a bronchus enter the lung. While the apex itself is not synonymous with the hilum, it is in close proximity to it. The apex of the lung is also associated with the adrenal gland as it is a region that lies close to where the adrenal gland sits atop the kidneys. Moreover, the lungs, including the apex, are enveloped by pleurae and contain alveoli or air sacs, which are crucial for the lung's function in gas exchange.