Bio Week 9 PDF

The Respiratory System Anatomy: Primary function is to move air from the atmosphere into our lungs via the process of ventilation so it can be then transported to our cells. Our cells can use the oxygen there and then the system is also...

The Respiratory System Anatomy: Primary function is to move air from the atmosphere into our lungs via the process of ventilation so it can be then transported to our cells. Our cells can use the oxygen there and then the system is also responsible for removing waste products in the form of carbon dioxide. Also referred to as: The upper respiratory tract which is everything from the nostrils through to the pharynx. The lower respiratory tract which is the larynx down to the alveoli. The area is sterile, so no normal flora will be present unless something has gone wrong.  There are a lot of blood vessels in the tissues here. The Sinuses: These are four pairs of air filled spaces that are around the nasal cavity. These spaces help warm and humidify the air a bit Sits behind the nasal cavity and its function is to Chanel the air from the nasal cavity into the larynx and to help warm and moisten and filter air. The pharynx can be divided into three parts: - Nasopharynx - Oropharynx - laryngopharnyx  Vocalisation is the noises we make Cartilaginous chamber has rings of muscle around which is our vocal cords. The glottis and Laryngeal muscles are in charge of sound modulation The epiglottis prevents food and drink going down the trachea by covering it. In front of the oesophagus The trachea is held open by cartilage so that it is always open  the tubes for air enter through openings in the lungs called the hilum the cardiac notch is a space that is missing to give the heart somewhere to sit. Our airways come down through the trachea into the lungs and form what we call the bronchial tree. trachea comes down and splits into 2, called the bronchi. They then split into the lobar bronchi (RX3, LX2). It continues to divide and get smaller and smaller. The bigger sizes are surrounded by cartilage to help hold them open and give them more strength. The smooth muscle allows us to either contract or dilate those airways. The lung splits until we get to the alveoli.  the job of the liquid is to help gases diffuse back and forth across the membrane surrounding the alveoli. The other thing that helps with gas transfer is the membrane surrounding the alveoli. These membranes are very very thin, less than half a millimetre thick which makes it easy for things to diffuse. Function  Very dry air or very cold air is irritating to the tissues in our lungs especially the tissues of the alveoli. The airways carry air from the nostrils, the insides are vascular so there is lots of blood flow through the tissues there. The blood is warm, body temp so the air is passing through the tissue there is being warmed by that blood flow. Mucous Membranes are damp because they secrete mucous onto the surface of them and it is sticky. So as the dry air passes over those surfaces, it’s picking up some of that moisture and it’s being moistened. Nasal Conchae - three lumpy objects embedded inside our nasal cavity and the job is to slow down and disrupt air flow, making it turbulent, which makes its spend more time with the Vascular epithelium and Mucous Membranes Nasal hairs act as filter for pathogens and trap them. L Shaped Bend ensures that air spends as much contact time as possible with our mucous membranes.  Goblet cells are making mucus, secreting it onto the surface of these membranes which act as our sticky trap. Mucous Membranes also have Cilia, which is sweeping back and forth incredibly fast all the time and they help sweep the trapped pathogens or debris towards the pharynx. Once we get a build up of that stuff, our body triggers a cough which will help expel things from the body or loosen it from the membrane which allows us to swallow it and it can be destroyed by our stomach acid.  Epiglottis and the larynx has the job of excluding solids and liquids from getting into our trachea. Trachea transports gases to and from the lungs, the oesophagus transports food and drinks to the stomach. Choking is where something gets into the trachea and stops us from breathing. The defence mechanism is little rings around the cartilage at regular intervals and their job is to hold the trachea open all the tome. The C shape is help together by the Trachealis Muscle which is expandable so if something is large enough to make us choke and gets lodged into our trachea, it’s expandable so the muscle can relax and make it a bit bigger which will allow us to move that blockage out.  Ventilation Because of gravity, the contents are always pushing outwards on the walls of the container. More stuff we put in the container, the higher the pressure that stuff exerts on the container. If the air pressure is the same inside the jar as outside, we call this one atmosphere (760mmHL) Half the jar size equals double the pressure. HIGH TO LOW PRESSURE. MOVEMENT WILL STOP AT THE POINT WHEN PRESSURE EQUALISES.  Inhalation or Inspiration is the movement of air from the atmosphere into the lungs. The second part is Exhalation or Expiration and is the movement of air from the lungs to the atmosphere. In normal circumstances, the type of breathing we do is called quiet or tidal breathing. Visceral Pleura is a serous membrane that forms a sac that surrounds the lungs. This is actually stuck to the outside of the lung. Both are flexible, they can expand and contract. The Parietal Pleura is another serous membrane and it forms a bigger area around the visceral pleura. The Parietal Pleura sticks to the ribs and to the sides and to the diaphragm muscle at the bottom. Between the two of them, we have the intrapleural cavity.  The first step involves the intrapleural cavity. It involves the parietal pleural. The Diaphragm muscle at the bottom pulls downwards by about a cm. At the same time, external intercostal muscles which are attached to the outside of the ribs pull the ribs outwards and upwards. Both of these things together have a strong effect of making the intrapleural cavity expand because they’re stretching the parietal pleural outwards. This makes the air pressure in the cavity drop because we still have the same volume of gas in that space. Now that space has gotten bigger and the effect of that is to create a pressure gravity. Now that the pressure inside the intrapleural cavity is lower than the pressure inside the lungs, the lungs will try to expand to try and even out the pressure gradient between the intrapleural cavity and the alveolar pressure inside the lungs. The lungs expand which means the air pressure drops a little because there is a bigger space holding the same amount of gas. This has evened out our pressure gradient between the intrapleural space and the lungs. Doing this has created a new pressure gradient because the pressure inside the lungs has dropped so it is now lower than the pressure of the air in the atmosphere. The air is sucked into the lungs and the air pressure in our lungs will rise due to more gas being in that space. The pressure gradient will even out and we will have a resting state again.  The diaphragm relaxes and returns to normal position and at the same time the external intercostal muscles relax, and the ribs return to their normal position. Passive Process When we relax and everything goes back to where it was before, the intrapleural cavity constricts which means the air pressure in there rises because we now have the same volume of gas in that cavity. In a smaller space, this means we have a concentration gradient. Now that the intrapleural cavity is higher than the pressure inside the lungs. Now the lungs are going to respond by trying to even out the pressure gradient and they’re going to do it by constricting back to their original position. As they do, the air pressure in the lungs is going to go up because we’ve got the same volume of gas in the lungs. But now that the lungs are is smaller, and as that pressure goes up, that creates a new pressure gradient where the pressure in the lungs is now higher than the pressure in the atmosphere. The air will then be expelled from the lungs to try and drop the air pressure of the lungs to the point where it evens out with atmospheric air pressure. These are actual measurements of the theoretical pressures inside the intrapleural cavity and inside the lungs which is labeled as alveolar air pressure. The atmospheric air pressure always stays about the same.  Gas Exchange Partial pressure is different types of pressure. Total pressure is all the pressure sources totalled together. The air that we are breathing in or out is a mixed gas made up of different types of things. We can also have partial pressure gradients.  Connected via our circulatory system. Two types of gas exchange. External Respiration occurs between the lungs and the blood (External because the air that is in your lungs is really external to your body - just part of a big tube that is going in and out from the atmosphere) Internal Respiration occurs between the blood and the cells From the lungs into the blood, from the blood into the cells, from the cells into the blood and then the blood into the lungs. Simple Diffusion drives this by partial pressure gradients of oxygen and carbon dioxide.  Oxygen will go from the alveoli in the lungs into the blood stream. We have a high partial pressure of oxygen in the air and the lungs and a low partial pressure of oxygen in the gases that are in the blood. Carbon dioxide has a high partial pressure in the blood, low partial pressure in the air in the lungs so it will diffuse into the lungs. The blood coming to the cells has just been oxygenated by the lungs. The cells have been carrying out operations to make energy. So they have just burned up all their oxygen and created a lot of carbon dioxide waste, The gas there is low in oxygen, high in carbon dioxide and the blood supply there. Though it is coming from the lungs, it’s oxygenated now, so it is low in oxygen. Oxygen will diffuse from the blood into the cells and carbon dioxide is going to diffuse from the cells into the blood. *High to Low pressure diffusion The Respiratory system can be divided into 2 parts: The conducting zone and the respiratory zone This conducting zone is there to make up volume and this includes the nasal cavity, the pharynx, the larynx, the trachea, the bronchi, the bronchioles and the terminal bronchioles. There is no gas exchange happening here, How much air is available to us for gas exchange rather than how much is just moving around.  Gas Transport The mechanism for transporting gases through our body is our cardiovascular system. These gases are moving oxygenated blood from the lungs to the cells and deoxygenated blood rich in carbon dioxide from the cells back to the lungs. The heart is what drives blood around. Oxygen moving in the blood is arterial blood that comes from the heart and is oxygenated. There is a concentration of 20ml of oxygen to 100ml of blood. Most of the oxygen is transported by binding to haemoglobin molecules inside red blood cells. That binding of those iron molecules to oxygen that forms ironoxide which gives blood that bright red colour. Haemoglobin starts its life as a deoxyhaemoglobin. Oxyhaemoglobin can bind up to four different molecules of oxygen. Once it is oxygenated, it is called oxyhaemoglobin 2. As oxygen binds to deoxyhaemoglobin it changes the shape of that molecule. That shape makes it easier for more oxygen molecules to stick to the haemoglobin group in that molecule.  Partial Pressure of oxygen Percent saturation of oxygen is how much of all the haemoglobin and our blood supply is actually full of oxygen. The higher the pressure, the more of our blood is full of oxygen (starts off slow and then increases. As the first oxygen molecule binds, it grows quite rapidly and then slows at the top. Oxygen saturation in our blood is determined by the partial pressure of oxygen in the blood. The curve can be affected by a few things that affect haemoglobin’s ability to bind to oxygen including how much carbon dioxide is in the blood, what the pH of the blood is and how warm the blood is. If your body is cold, alkaline and there is not much carbon dioxide, oxygen will bind easier to that haemoglobin and want to stay with it. If the blood is warm and low in pH or higher in Carbon Dioxide, the oxygen is more likely to become dissociated from the haemoglobin and be used for other things. FOR EXAMPLE: if we have muscle cells that have been doing a lot of cellular respiration, that area will be warm as the by-products of cellular respiration is CO2 and heat. The O2 molecules stuck to our haemoglobin are much less resistant to becoming detached from the haemoglobin so they are free to be used for other things. C02 is the byproduct of cellular respiration. Carbon Dioxide is in the blood because cells perform cellular respiration to make energy. The by-product of that is carbon dioxide which those cells need to get rid of. There will be lots of CO2 in the cells and not in the blood, so the CO2 will diffuse out into the blood and be transported away. Oxygen attaches to HAEM group, CO2 attaches to amino groups inside the RBC’s. The majority of CO2 gets transported as Bicarbonate ions (HCO3-). SO CO2 comes out of the cells that have been doing cellular respiration and into the bloodstream. The bloodstream contains a lot of liquid. The Carbon Dioxide will dissolve into the watery part of the blood, forming a new chemical known as Carbonic Acid. But the Carbonic Acid is not really stable in that environment so it spits it back out and forms two things; bicarbonate ions and hydrogen ions. There is where we get the bicarbonate ions in our blood so must of our carbon dioxide is travelling here in the form of bicarbonate ions. Because we can’t exhale bicarbonate ions and hydrogen from the body, it has to be reconverted so it flows back the other way again. As it reaches the lungs, it actually encounters an enzyme called carbonic anhydrase and that causes the bicarbonate ions and the hydrogen to be recombined to carbonic acid which will then split apart into carbon dioxide and water. The carbon dioxide can be exchanged with the lungs and then exhaled. The pH will last until we can get rid if those hydrogen ions by breathing out which means we have less carbon dioxide in the blood. Blood pH should be around 7.35-7.45 PH can be changed in seconds to minutes in short term control. There is a longer term control on pH levels in the blood and the cerebral spinal fluid which is closely ties to pH of the blood which is done via the Kidneys. When you’re sleeping, your cells are doing less work which means they are producing less CO2. The CO2 will get into your blood and make the blood more alkaline - a bit higher. Your body doesn’t want that though and will make changes to revert back to normal. What actually controls your breathing? Breathing is autonomic - we do it subconsciously and are not thinking about it. Breathing is an autonomic reflex. There are three sets of sensors that detect what needs to happen. These receptors inform what is going on with our breathing without us even knowing about it. They are always signalling to our nervous system which sends it to our respiratory reflex centre which sit in the Pons in the Medulla Oblongata. Reflexes require an efferent side to make effects in the body to make sure breathing occurs. Signals are coming out that control our Alveolar ventilation rate and depth which happens via control of our respiratory muscles. Signals for vaso - dilation and constriction. The respiratory centre also controls our cough and sneeze reflexes. Chemoreceptors monitor levels of chemicals in the Cerebrospinal Fluid and in the blood. The urge to breathe is triggered by these receptors and levels of hydrogen ions and carbon dioxide are a powerful trigger in a breathing reflex, more so than oxygen. When the chemoreceptors detect high levels of CO2 and Hydrogen in the CSF and to a lesser extent in the blood, they will send a signal that it is time breathe out. Getting rid of the CO2 is a more powerful need than to get the O2 back in. Acidosis is a biological process increasing the concentration of hydrogen ions in the blood. Alkalosis is the opposite. Low levels of CO2 (Hypocapnia) is dangerous due to the lack of a signal sent to the brain to breathe. Free diving is dangerous because they hyperventilate before to breathe out as much CO2 as they can but because they have very little CO2 left, the alert for oxygen does not go off because they’re low in CO2.  Vasodilation increases blood flow because there is more blood flowing there which means more gas exchange has to occur. We have to increase respiration rate to keep up with that. Vasoconstriction decreases blood flow which means less gas exchange is required and your body will decrease your respiration rate because it doesn’t need to breathe in and out to keep pace with that. Pontine Respiratory Group located in PONS and regulates the depth of our ventilation. Dorsal Respiratory Group located in the Medulla and regulates ventilation and respiration rates (how often we breathe, muscle control of those used in quiet breathing, diaphragm and external intercostals) Ventral Respiratory Group - helps with forced breathing, accessory muscles, our internal intercostal muscles.  We can take control of our respiratory system. You can override the signals from the autonomic system and choose to hold your breath, breathe faster and deeper. This is when the cerebral motor cortex appears towards the upper brain, kicks in and starts overriding signals coming from our respiratory reflex centres so that can drive conscious control of our respiratory muscles. As pH drops, Haemoglobin saturation decreases. During external respiration, Carbon dioxide moves from blood to the alveoli.