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The hilum of the lung is a triangular impression that allows the structures which make up the root of the lung to enter and exit. A hilum is a section of an organ where other types of structures like veins or arteries can enter. The hilum of the lung is a wedge-shaped section in the central area of the lung that permits arteries, veins, nerves, bronchi, and other structures to enter and exit. Both human lungs have a hilar region, meaning both lungs have an area called the hilum. This region aids the lung's root in anchoring the lungs to the heart, trachea, and other structures.
Lungs are organs of respiration and are part of the respiratory system. They pull oxygen from the environment and transport it into the bloodstream. The lungs are soft elastic organs that are lightweight when their tissues are healthy. Humans have two lungs, one on either side of the chest cavity, which are separated from each other by the heart and trachea. The area where the heart, trachea, and other structures are located is called the middle mediastinum.
Air reaches the lungs via the trachea, which is commonly called the windpipe. In humans and some other animals, the trachea is a tube that connects the lungs to the upper part of the respiratory system, which consists of the mouth, nasal cavity, pharynx, and larynx. When the trachea reaches a point in the mediastinum called the carina, it splits into two tubes called the primary bronchi. The right and left primary bronchi enter the corresponding lung and subdivide into more bronchial branches.
Each lung can be divided into four main sections: the apex, base, root, and the hilus or hilum of the lung. The apex is the uppermost part of the human lung, and it is rounded in shape. It extends as high as the bottom or root of the human neck and as low as the first rib. The base of the lung is wide and concave and sits on the surface of the diaphragm.
Above the middle mediastinal area is the root of the lung, which connects the lung to both the trachea and the heart. The root of the lung is composed of several structures including the pulmonary artery and pulmonary veins, all of which are encased in a layer of pleura, which is a thin smooth layer of protective tissue. The hilum of the lung is the root's point of attachment to the lung. The area surrounding the hilum of the lung is called the perihilar region.