Let's dive into figuring out of how our body harvests respiratory gases from the atmosphere.
Please print out the lecture handouts (in your desired format) and ideally also the pre-view questions before watching the videos. Please send me the questions to email@example.com before class. Thanks.
Preview Questions: (printable version) 20.1. The respiratory system consists of the lungs and deals with gases. It extracts oxygen from the atmosphere. What main gas does it get rid off? 20.2. A main function of the respiratory system is to keep blood’s acidity (measured as pH) within a narrow range, which means, the body has to finely control the H+ (hydrogen ion) concentration. As cell’s break down glucose to harness energy (ATP), carbon atoms split off and combine with oxygen to form carbon dioxide (CO2). CO2 combines with water (H2O) forming carbonic acid (H2CO3), which can then split into bicarbonate ions (HCO3-) and H+. Interestingly, bicarbonate ions act reversibly, they either pick up or release H+, depending on their concentration. As CO2 concentrations rise, H+ do as well. In the lungs, the body breathes out the CO2, effectively decreasing the H+ concentration, and therefore decreasing blood acidity. Which other organ helps balance the body’s acidity via the production of bicarbonate? 20.3. Air contains oxygen, which the body extracts within the alveoli of the lungs and pass it on to the bloodstream, which then delivers it to the cells. In order to get deep into the lungs, where oxygen can be exchanged, air has to travel from the nose (or mouth) through a series of passageways. What is that area (zone) collectively called that ventilates the lungs? 20.4. The upper air passages, mainly the nose and pharynx not simply channel air towards the lungs, but they also warm, humidify, and purify the air we breath in. How does the body keep these passageways moist? 20.5. Nasal conchae within the nasal cavities are bony flaps covered with highly vascularized tissue. They are shaped in a way that when we breath through the nose, the air has to circulate and slow down. How do they help the body prepare the air for the lungs? 20.6. Sinuses are air chambers within the skull that help warm air and give volume to one’s voice. All the sinuses connect to the nasal cavity into which they drain. If they get infected and mucous blocks their opening, the pressure inside them builds up creating pain (sinusitis). Which sinuses are most vulnerable to such infection and why? 20.7. The posterior part of the nasal cavity becomes the pharynx, which leads all the way down to behind the bulge one can feel in front of the neck. Behind that bulge (more prominent in men and known as the Adam’s apple) is an area where we create voice (vocalization). What do we call the voice box? 20.8. Within the voice box, two vocal cords span from front to back (anterior to posterior). As air passes by them as we exhale, they vibrate and create voice. Vowels (a,e,i,o,u) are created within the voice box. Where do we form consonants? 20.9. The epiglottis is a cartilage flap that points upward. When we swallow, it descends covering the windpipe. Why would that be helpful? 20.10. Below we find the trachea, a tube filled with horseshoe shaped cartilages that are open in the back. They help keep the windpipe open since air is not strong enough to push it open when we breath. Why do the tracheal rings not close posteriorly (in the back)? 20.11. Once low enough, the trachea splits into two bronchi, a left and right one, each feeding a lung with air. They split into ever finer branches, getting smaller and smaller, until they reach areas where gas exchange takes place. What are the grape-like air sacs called? 20.12. Remember when we talked about the heart, I had you visualize pushing a fist into an air-filled balloon to demonstrate the continuous serous membrane that on one side attaches to the organ, and on the other to the body wall. In the heart, that membrane was the pericardium. What is it called in the lungs? 20.13. In the heart, the serous membrane mainly reduces friction. In the respiratory system, it also helps keep the lungs suctioned to the chest wall, so that when the chest expands, the lungs passively follow and fill up with air. If something breaks the membrane, a broken rib for example, the affected lung collapses and can’t fill up with air, making breathing more difficult. What is that condition called? 20.14. The right lung has 3 lobes, the left only 2. Why is that? 20.15. All the ‘pipes’ (blood vessels, nerves, and bronchi) enter/exit the lungs at the same place, medially, by the mediastinum. What is the ‘root’ of each lung called? 20.16. Pulmonary vessels connect the heart to the lungs bringing blood close to the alveoli for gas exchange. Which one (artery or vein) carries oxygenated blood from the lungs back to the heart? 20.17. As we inspire, the chest cavity expands outward, but also downward (the often forgotten belly breathing). Which muscle is mainly responsible for increasing the cavity inferiorly? 20.18. We describe different respiratory volumes depending on how deep one breathes. Quiet breathing without much exertion is called tidal volume, during which only about half a liter of fresh air exchanges the lungs. More rigorous breathing is possible and described as inspiratory as well as expiratory reserve volume. Up to how much extra air can be exchanged when we breath as heavy as possible? 20.19. Gas exchange between air and blood happens within the tiny air sacs (alveoli), where alveolar cells (type 1 pneumocytes) cling to capillaries. Another cell type, type 2 pneumocytes, secrete surfactant to help keep the small spheres from collapsing due to tension created by hydrogen bonds between the water (H2O) molecules. What is the function of a third cell type called dust cells? 20.20. Respiratory gases (O2 and CO2 mainly) travel between alveoli and blood vessels by diffusion. Remember, diffusion is a passive process where a solute (here O2 and CO2) moves down a concentration gradient. Do you expect the concentration of O2 to be higher in the alveoli or the capillary?
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