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Lecture 8

DEV2022: Lecture 8 notes

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DEV2022 – LECTURE 8 (RESPIRATORY SYSTEM ANATOMY) Lungs: left and right: Lungs are a very spongy organ. Most of the lungs are the spongy material, which are made up of the alveoli, and you’ll also be able to see large holes in it, which are the air holes, or bronchi, or arteries/veins. Big arteries and veins hang out in the middle. Lung structure: general lay-out: Lung parenchyma is the general tissue of the tissue which is made up of gas exchanging units, or the alveoli. Wrapped around the lung is a thin elastic membrane with collagen in it, which keeps all the gas in (gas type barrier) = visceral pleura. The lung is entirely sealed. It has to be elastic as the lung changes a lot, when you breath – volume and size of the lung changes a lot Section through lung parenchyma: The small gas sacs are the alveoli. Bronchioles are small airways, which conduct air from the trachea to tiny sacs We also have small veins and arteries because the lung actually weighs a couple of kg, and it carries as much blood per unit time than the body put together. Because the lung takes the entire output of the right side of the heart, the rest of the body takes the entire output of the rest of the heart, and those two outflows are the same because the pump of the heart works in series. The cardiac output of the lung is the same to the rest of the body. Highly vascular organ, hence why injuries to the chest is often fatal. Gross anatomy: right lung lobes: Lobes differ to left and right side, as well as different species. However, the lobes have similar functions. Gross anatomy: Left lung lobes: It has a great indentation to it because that's where the heart sits. The bottom of the lung is kind of curved to fit the diaphragm. Pleural membranes: The pleura is the membrane that wraps right around the lung, so it's the skin of the lung. On the chest side, it contains a parietal pleura, which lines the thoracic wall. These two membranes must be able to move so we can contract our lungs. The hilum is the top of the lung, which is the point where the two membranes join together. Pleural cavity: The pleural cavity is the imaginary space between the two pleura (visceral + parietal). It is only a real space when you have a puncture wound in the chest, which allows air in and the lung recoils/retract, and air will go in and sit in that pleural cavity. When you get air in the pleura cavity, you can’t breathe. When we breathe, the diaphragm muscle contracts. At rest, the intrapleural pressure inside that lining is negative (subatmospheric) When we breathe in, we lower that pressure and that makes the lungs expand. Ventilation: Inspiration is an active process that largely involves the diaphragm. The diaphragm contracts due to the phrenic nerve activity. The external intercostal muscle play some role. When we breathe in, it has to do with the diaphragm and the intercostal muscle – it has nothing to do with the abdomen. When we breathe out, the diaphragm does nothing, it relaxes. The external intercostal muscles relaxes. When we’re exercising and we need to breathe hard, the best way is to contract the abdominal muscles. Only expiration may involve abdominal muscles, but not inspiration. Lung hilum: Hilum is the top of the lung where the two lungs are joined together, and its where all the vessels and plumbing goes, so its where the bronchi go into the lung and also where major pulmonary veins and arteries go into the lung. Bronchi is the big airway. Pulmonary blood supply: Lung receive a huge amount of blood so they have very large vessels. They have 2 large arteries and 2 large veins. Pulmonary veins to left atrium Pulmonary arteries to right ventricle Functional zones of the lung: Conducting zone is the airways, its just the tubes that carry air into the lungs. The biggest tube is the trachea that divides into the bronchi, where the major bronchi divides into bronchioles, until we get the terminal bronchioles. The terminal bronchioles are the smallest bronchioles that don’t take part in
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