Lung: The lungs are cone-shaped organs of respiration which like in the thoracic cavity, one on either side of the mediastinum. The rounded upper portion of each lung is called the apex; the base is the concave lower portion resting on the diaphragm; and the hilus is the area on the medial surface through which the main bronchus, pulmonary artery, pulmonary vein, nerves, and lymph vessels enter and leave each lung. The left lung is partially divided by a fissure into an upper and lower lobe. Projecting from the lower portion of the left upper lobe is an area called the lingula (coded to left upper lobe). The right lung is divided by two fissures into three lobes (upper, middle, and lower). Visceral pleura or mesothelium covers the outer surfaces of the lungs and adheres to them. Parietal pleura or mesothelium lines the thorax. The potential space between the visceral and parietal pleura is called the (inter) pleural space or pleural cavity. The pleural space contains a lubricating pleural fluid which eliminates friction during the breathing process. This fluid drains to the mediastinal nodes. When the mediastinal nodes become inflamed or involved with a disease process such as a malignancy, a pleural effusion develops. Breathing then becomes labored and painful. The lungs provide a place where large amounts of oxygen can be loaded quickly into the blood and large amounts of carbon dioxide can be removed from it. The pulmonary artery from the right side of the heart branches into two arteries which carry deoxygenated blood to both lungs. Each artery continues dividing and subdividing within the lungs forming smaller and smaller vessels which end in capillaries which surround the alveolar sacs of the respiratory bronchioles. As the blood passes through the pulmonary capillaries, it absorbs oxygen and releases carbon dioxide. Then the newly oxygenated blood immediately returns through the venules (small veins) to the pulmonary veins which return to the left side of the heart. The lung itself gets its nutriment supply from the bronchial arteries which branch off the aorta. All regional nodes for the lung and the pleura are above the diaphragm. They include the intrathoracic, scalene, and supraclavicular. The intrathoracic lymph nodes can be divided into two main groups: intrapulmonic and mediastinal.