The bronchovascular bundle consists of bronchioles, arterial trunks with surrounding connective tissue extending from the hilum and perihilar region to the most peripheral lobular anterior bronchioles, and these structures become thinner with each bifurcation. The vessels and bronchi are usually easier to identify on high-resolution CT (HRCT). On CT images, the artery appears as a branching linear image along its main axis, gradually becoming thinner from the center to the periphery. Bronchial images in the same plane appear as lines running parallel to the arteries; in cross-section, arteries appear as white dots, often next to small annular shadows representing the same color of the accompanying bronchial walls. The pulmonary veins are also involved in forming part of the different lung types and their course differs from that of structures such as arteries and bronchi. The pulmonary veins flow into the left atrium under the pulmonary hilum, with small branches that converge into the main venous vessels in a single branch. Branches around the central interlobular stroma, namely the central lobular artery and the fine bronchi, enter the central part of the secondary lobules; on CT, the central lobular artery, which is located in the center of the lobule, is often visible, while the fine bronchi are not. This is because the thickness of the fine bronchial walls is less than the spatial resolution of CT.