PHYSIO REVIEW: RESPIRATORY SYSTEMLecture One notes: Organization of Respiratory systemDifferent sets of muscles for expiration and inspiration**During inspiration primary muscle is the diaphragm and external intercostal muscles. Diaphragmsits between thoracic cavity and abdominal cavity. It typically sits in a position in its relaxed state in which it kind of has a dome into the thoracic cavity, as we contract the muscles of the diaphragm, they shorten and in doing so causes the diaphragm to pull downward and flatten out, this increases the volume of the thoracic cavity. Also these intercostal muscles, (found between the ribs) when those are contracted this causes the rib cage be pulled up and outward, again increasing the volume of the thoracic cavity. These are the primary muscles used during passive inspiration. Active inspiration: additional muscles are used-sternocleidomastoid muscles and scalenes, additional muscles in the neck and shoulder region that attach to upper part of rib cage and that adds additional force to open up the rib cage more than it would under passive conditions. Muscles of expiration; passive expiration, quiet no extra metabolic demand—no muscles required, its simply a relaxation of the inspiratory muscles. The recoil of the elastic lung, allows for expiration. However active expiration requires quicker movement, involves abdominal muscles and internal intercostals-also sit outside rib cage, when they are contracted they pull rib cage in.Right lung divided into three lobes, left lung divided into two lobesCardiac notch in left lung, because heart sits primarily to the left middle of chest, takes up volume and space in left hemisphere of lung. Right lung larger than left, about 60% of oxygen from right and 40% of oxygen from left lung.These splits in lung helps the mobility of the lung, as we are breathing we are doing a lot of moving so these splits in the lung give a little mobility to it, so they don’t rub against each other and independently move.Want to make note of space between lung and left wall, thereare two plural membranes associated with this space.One pleural membrane is tight and close to the thoracic wall or inside rib, so attached to the innersurface of ribs and the other is attached to the lung itself. Space between these two is called the pleural space and it is filled with a pleural fluid. This fluid layer helps hold lungs tight against thethoracic wall due to the cohesiveness of water- water covalently holds together. This fluid layer holds the lung tight to the chest wall, therefore when the chest wall moves the lung moves! So this is what pulls lung open and allows air to flow in. Right pleural space not connected to left pleural space.Functions of airway:Air way or conducting airway is responsible for warming air to body temp. Also airways important for adding water vapor and bringing humidity up to 100%, humidity important to maintain integrity and viability of tissue. Conducting airway starts at the trachea down to the lung, important for filtering out foreign materials-anything we breathe in, in the airTrachea has a single tube that comes down into thorax or chest and then it bifurcates into left and right bronchi, further we go distally we get more and more branches all the way down into bronchioles and alveoli, no cartilage to protect airway near alveoli so therefore this area is collapsible- can collapse under various disease conditions and respiratory environments.About 24 divisions on average, diameter gets smaller as you go down, but the total number of these branches increase exponentially. If we take the cross sectional area, the area of that as we move down the airway increases (cross sectional area of all branches), as individual area decreases. So as we go further down total cross sectional area increases this means that air flow velocity decreases as we go distally in air way because effectively total cross sectional area is getting bigger and flow slows down, better for gas exchange to occur and diffusion to become effective. Down in exchange are we decrease air flow velocityIn this part of the airway there is not gas exchange but there are specialized cells-ciliated epithelial cells- line inner airway of conducting airway. These are quite affective, they sit within this watery saline layer, that way they can move quite freely, there are these goblet cells that secrete mucus, this mucus secreted and b/c of the low density of it, it floats on top of this saline watery layer. Therefore mucus picks up any dust particle etc that are breathed in, so mucus layer traps inhaled particles. These cilia move unidirectionally, they move this mucus and saline layer up and out of our airway, helps to keep clearing our airway of any unwanted matter that comes in. Cigarette smoking paralyzes cilia in the airway, leads to a cough—cilia decrease to less than100 times per minute. Smokers have an increased production of mucus to go along with the decrease movement of the cilia.Smoking is the primary cause of a lot of respiratory diseases. This saline layer that is formed on top of the cilia: when talking about the transport of ions and water to maintain this saline layer, since its always moving up and out this saline layer needs to be maintained, so the sodium potassium chloride pump is responsible for that. They initially down in the basal side of epithelium side allow the movement of chloride into the cell as it moves in it diffuses out to the apical side of the cell, and here we have anion channels including the CFTR (cystic fibrosis transmembrane regulator) allows chloride ions to enter lumen. so chloride transported into cell atthe basal layer diffuse to apical layer where a channel allows it to move into the air space into the saline layer so once we get a chloride ion here what happens is we have sodium passes through the ECF (extra cellular fluid) to the lumen through a paracellular (paracellular meaning between the cells) pathway, this pathway is drawn by an electrochemical gradient– because of the negative charge of the Cl- ion it attracts the positive charge of the Na+….so once Na+ moves into the space following Cl- ion, then that makes NaCl which draws water through the paracellular pathway, and moves it up so now we have saline– now have saline layer. Cystic fibrosis involves a mutation in thisCl- anion channel—becomes defect and limits or inhibits chloride from coming into the anion channel. If Cl-