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Lecture 2 (Muscles used during breathing (Inspiration: diaphragm, external…

- - - - Cartilaginous rings keep the larynx and trachea from collapsing
        Primary bronchi branches about 24 times (brown parts are collapsible)
        Branching of airways increases the number of branches, total cross sectional area, and decreases air flow velocity
        Diaphragm is a skeletal muscle, contracts (flattens out), relaxes (curves)
- - - - Mucociliary Clearance (elevator):
        Airway Epithelium facilitate warming, humidifying, and filtering of air as it passes towards alveoli
        
        Filtering: sticky mucus along surface of conducting airway, particles get stuck in mucus, elevated up and out of lung
        
        Elevator: lining of airway, epithelial (separate compartments), made up of a single layer of cells. Goblet cells are between cilia, produce mucus.
        Cilia at end of cells, motile system coordinates pushing fluid, surrounded by pericilliary saline fluid.
        
        If we don't have normal function of the elevator, extremely likely to develop infections. Only one cell layer to outside environment
        
        Active trans-epithelial chloride secretion produces the saline (pericilliary) layer Without this, mucus gets thick, infection is likely (occurs in people with CF)
    - - Terminal Bronchiole:
        Has smooth muscle
        No Alveoli
    - - Respiratory Bronchiole:
        Has Alveoli
        Elastic fibers allow alveoli to return to normal size (elastic recoil) active inspiration/passive exhalation (resting)
        
        Type I alveolar cells:
        Flattened out
        Thin
        Gas exchange
        Air as close to blood as possible (capillary beds between each alveoli)
        Single sheet of blood between the alveoli (not seen in any other part of the body)
        
        Type II alveolar cells:
        Secrete surfactant (creates mucus)
        If a new type I cell is needed these can differentiate into one.
        Equal # of type I and type II
        
        Alveolar Macrophages:
        protective mechanism
        wander around surface of alveoli
        
        Thin film where surfactant is on
        Same gas pressures from alveoli to alveoli
      - Bronchiole circulation is a branch of systemic circulation
        Bronchiole artery and vein
        Bronchiole nerve (some control over this, central/local)
        Lymphatic vessel: gets rid of fluid in lungs (interstitial space)
      - Optimize gas exchange by making distance as short as possible, large surface area
        Less than 1 micron = fast diffusion