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Air then travels continuously from the air sacs at the back, through the lungs, which are relatively fixed in size, to the air sacs at the front. From here, the air is exhaled. These fixed size lungs are called "circulatory lungs", as distinct from the "bellows-type lungs" found in most other animals. [106] [108]
A pulmonary contusion is a bruise of the lung tissue caused by trauma. [35] Damaged capillaries from a contusion can cause blood and other fluids to accumulate in the tissue of the lung, impairing gas exchange. Pulmonary edema is the buildup of fluid in the parenchyma and alveoli. An edema is usually caused by left ventricular heart failure, or ...
The pulmonary arteries carry deoxygenated blood to the lungs, where carbon dioxide is released and oxygen is picked up during respiration. [3] Arteries are further divided into very fine capillaries which are extremely thin-walled. [4] The pulmonary veins return oxygenated blood to the left atrium of the heart. [3]
The lungs expand and contract during the breathing cycle, drawing air in and out of the lungs. The volume of air moved in or out of the lungs under normal resting circumstances (the resting tidal volume of about 500 ml), and volumes moved during maximally forced inhalation and maximally forced exhalation are measured in humans by spirometry. [12]
A capillary is a small blood vessel, from 5 to 10 micrometres in diameter, and is part of the microcirculation system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the tunica intima (the innermost layer of an artery or vein), consisting of a thin wall of simple squamous endothelial cells. [2]
Arteries branch into small passages called arterioles and then into the capillaries. [19] The capillaries merge to bring blood into the venous system. [ 20 ] The total length of muscle capillaries in a 70 kg human is estimated to be between 9,000 and 19,000 km. [ 21 ]
The capillaries are responsible for allowing the blood to receive oxygen through tiny air sacs in the lungs. This is also the site where carbon dioxide exits the blood. This all occurs in the lungs where blood is oxygenated. [28] The blood pressure in blood vessels is traditionally expressed in millimetres of mercury (1 mmHg = 133 Pa).
These bronchioles give rise to the air sacs in the lungs called the alveoli. [10] The lungs are the largest organs in the lower respiratory tract. The lungs are suspended within the pleural cavity of the thorax. The pleurae are two thin membranes, one cell layer thick, which surround the lungs. The inner (visceral pleura) covers the lungs and ...