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Gas Exchange - Coggle Diagram

- - - - inflammation in lungs causes large mucus production
      - increased mucus provides breeding ground for bacteria
    - - persistent coughing causing stiff tissue and structural damage
      - less functional alveoli
- - - - inspired air is not used for gas exchange with blood even though it reaches alveoli
      - sometimes absence of blood flow
    - - conducting airways have an area of no gas exchange
      - larynx, trachea, bronchioles, terminal bronchioles
    - - both anatomical and alveolar dead space
- - - - sea level= 760mmHg
      - air moves through conducting zones and becomes 100% saturated
      - water contributes to partial pressure entering lungs since it lowers partial pressure of nitrogen and oxygen
  - - - Air
        
        PO2- 160 mmHg
        
        PCO2- 0.23mmHg
      - Alveoli
        
        PO2- 100mHg
        
        PCO2- 40mmHg
    - - rapid diffusion(0.25 seconds)
      - thin membrane and close blood vessels
      - exercise- increased breathing and blood flow so equilibrium still reached
    - - PCO2 varies depending on activity and blood flow
      - large pressure gradients mean more gas exchange
      - during exercise PO2 is low and PCO2 is high
  - - - ratio of alveolar ventilation to pulmonary blood flow (Ventilation/perfusion)
      - in upright lung higher pulmonary arterial hydrostatic pressure at base than apex because of gravity
      - blood flow decreases 3x faster than ventilation
      - effect of obstruction on V/Q
        
        airway obstruction- blood gas content unchanged through capillary
        
        vascular obstruction- alveolar gas remains at atmospheric levels
        
        normally gas exchange is completed in capillary
- - - - Dorsal respiratory group
        
        located in the region of the nucleus tractus solitarius
        
        is active during respiration
        
        inspiration neurones control external intercostal muscles and diaphragm
      - Ventral respiratory group
        
        nucleus ambiguous
        
        neurones control muscles for active expiration and greater than normal inspiration for vigorous exercise
  - - - carotid bodies and aortic bodies
      - 2 cell types
        
        type 1- contact blood and communicate with afferent nerves
        
        type 2-"glial cell like" repair and supply nutrients
    - - ventral surface medulla
      - H+ stimuli pH change in cerebrospinal fluid, but the ions do not cross blood brain barrier
      - insensitive to PO2 changes
  - - - PCO2 stimulates chemoreceptors which increase breathing rate and depth
      - PO2 only stimulates in severe hypoventilation
      - arterial PO2 falls and PCO2 rise
    - - arterial PO2 rises adn PCO2 falls
      - chemoreceptors stimulation reduced which decreases breathing rate and depth
- - - - rigid tubes
      - made of cartilage rings to avoid collapsing
    - - terminal bronchioles are in the conduction zone, respiratory bronchioles and below are in respiratory zone
      - no cartilage, walls contain smooth muscle
      - sensitive to certain hormones and chemicals
    - - thin walled inflatable sacs
      - site of gas exchange
      - type I is 1 cell thick and type II secretes surfactant (a fatty lipoprotein complex that reduces work to inflate the lung)
      - Pores of Kohn allow airflow between neighbouring alveoli giving collateral ventilation
      - surrounded by mucus (to form the mucus escalator) and capillaries (which fuse with alveoli walls to create thin barrier)
    - - it is skeletal muscle
      - separates thoracic cavity from abdominal cavity
    - - it is doubled walled that separates each wall from thoracic wall and surrounds lungs
      - intrapleural fluid is secreted by pleura and lubricates the pleural surface
- - - - made of 4 polypeptide chains each with a haem group
      - levels can vary because of haemorrhages and anaemia
    - - sigmoidal shape
      - binding 1 O2 increases affinity of Hb for next O2, because of cooperativity
      - below 15mmHg Hb has a low affinity so low O2 saturation
      - increase PO2 Hb increases affinity
      - above 60mmHg few binding sites are available as saturation nears 100%
      - systemic veins are lowest at 40mmHg, so huge capacity to unload O2
      - affecting factors
        
        Temperature- increase causes shift right
        
        pH- decrease causes shift right (respiring tissues produce H+ which lowers pH so O2 unloaded
        
        2,3-DPG- it is produced during glycolysis and promotes unloading (shift right)
    - - O2 binding protein in skeletal muscle
      - one haem group for each chain
      - has higher affinity than Hb, at low PO2 it is 50% saturated, so shift far left
    - - blood flows to foetus via umbilical veins with O2 ~40mmHg
      - it has a greater affinity than adult Hb and there is an exchange at the steep part of the curve
      - has small difference between arterial and venous blood PO2
  - - - CO2 combines with H2O to form carbonic acid, by enzyme carbonic anhydrase in red blood cells
      - carbonic acid dissociates into H+ and bicarbonate ions