Lungs
The lungs are two distinct cone-shaped organs located in the thoracic cavity and are separated by the heart and mediastinum. The lungs are made up of a large surface area of convoluted, spongy, elastic tissue. Each lung is enclosed and protected by a double-layered serous membrane called Pleural Membrane :
Parietal Pleura lines the walls of the thoracic cavity Visceral Pleura lines the lungs themselves
Pleural Cavity is the space b/t the parietal and visceral pleura and contains a lubricating fluid secreted by the membranes reducing friction. Surface tension is the phenomenon where the two membranes adhere to one another. The caudal portion of the lung is called the base which is concave and fits over the diaphragm. The cranial portion is a narrow part called the apex. The surface against the ribs is called costal surface and the mediastinal (medial) surface contains the hilum. The hilum is where bronchi, pulmonary blood vessels, lymphatic vessels and nerves enter and exit the lungs. The left lung is ~ 10% smaller than right lung and contains 2 lobes whereas the right lung has 3 lobes. When the lungs are fully expanded, they can reach back as far as rib 16.
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