Respiratory Tract & Mucociliary Transport system

• Nose: 

  – moistens, warms and filters the air  

  – houses olfactory receptors (smell receptors)  

  - resonance chamber for speech 
•  

  Nasopharynx only deals with the air going through it 

  Oropharynx epithelium has to be tougher (stratified) 

  Trachea sits in front of the oesophagus 

  Larynx is voice box 

  Epiglottis stops unwanted substances going down the trachea  
• Vibrissae – very fine hairs which help filter out large particles from the inspired air. 
• Inside nasal cavity there are Nasal turbinates: (covered in mucus) slows down air flow to allow time for the nose to perform its functions. 

  Mucus contains antibacterial enzyme lysosign which also secretes defensins that are naturally occurring antibiotics 

   

  3 parts: 

  Superior  

  Middle 

  Inferior  

   
• Mucosa is the lining of the airways and upper respiratory tract which is richly supplied with sensory nerve endings. If there's a buildup of irritants (pollen) the sensory nerve endings may perform a sneeze to stop the irritants from getting further down towards the lungs 
• The bronchial tree – lower respiratory tract: 

  Trachea bifurcates into right and left bronchus – the point is caller the carina 

  Right main bronchus comes off at an angle of 20-30 degrees – more vertical 

  Left main bronchus comes off at an angle of 45-55 degrees - more horizontal 

  If a patient aspirates the lungs will get inflamed in a response to the unwanted substance cause could cause a reaction called aspiration pneumonia  
• Left main bronchi divides into lobar bronchi which supply a lobe of lung.  

  Then lobar bronchi divide into segmental bronchi which carries on 23 times 

  Conducting zone are all the airways which conducts gas into alveoli.  

  Smallest airway is the terminal bronchi in the conducting zone.  

  No gaseous exchange in conducting zone 
• Respiratory zone is distal to the conducting zone and starts with respiratory bronchioles which are distal to the terminal bronchioles. They're a hybrid structure, part airway, part alveoli where gaseous exchange takes place. 

  Resp bronchioles then lead to the alveoli (air sacs) where gaseous exchange occurs  
• Smooth muscle – down the conducting zone, if it contracts airway becomes narrower called bronchoconstriction. Narrows diameter of airways, more resistance to airflow 

   

  Hyaline cartilage – supporting structure to airways which decreases as it goes further down the airways. 

   

  Right lung – 3 lobes, upper, middle, lower 

  Left lung – 2 lobes, upper, lower 

   
•  

  Bronchopulmonary segments: each lobe of lung divides into bronchopulmonary segments  

   

  bronchopulmonary segments is an anatomically separate unit of long, with its own artery and vein surrounded by its own connective tissue sector.  

   

  Gravity assisted positioning to help drain specific bronchopulmonary segments in the lungs 

   
• RIGHT LUNG  

  • Upper lobe  

    – apical  

    – posterior  

    – anterior  

   

  • Middle lobe  

    – lateral  

    – medial  

   

  • Lower lobe  

    – superior  

    – medial-basal  

    – anterior-basal  

    – lateral-basal  

    – posterior-basal  
• LEFT LUNG  

  • Upper lobe  

    – apico-posterior  

    – anterior  

   

  • Lingula  

    – inferior  

    – superior  

   

  • Lower lobe  

    – superior  

    – antero-medial basal  

    – lateral basal  

    – posterior basal 
• Mucociliary transport: 

  Defense mechanism in the lung 

   

  Made up of 3 components: 

  1) Cilia 

  • Microscopic hair like process extending from the surface of a cell   
  • Capable of rhythmic motion  
  • Act in unison with other cilia to cause movement of cell or surrounding medium 
• Ciliated epithelium 

  • Ciliated epithelia in vesicles of brain 

    - circulate the cerebrospinal fluid  

   

  • Ciliated epithelia in oviduct 

    - move ova from ovary to uterus   

   

  • Respiratory tract ciliated epithelial cells  

    - sweep clean dust and germs trapped in mucus secreted by goblet cells (sits onto of the cilia) 

   

  Cilia extends all the way down the respiratory tract to the terminal bronchioles which are the smallest airways in the conducting zone of the lung 
• 2) Aqueous or sol layer 

  Watery fluid facilitating ciliary movement 

   

  Pulmonary Oedema – buildup of fluid in the lungs, adversely affect ciliary movement 

   

  Dehydration – impair ciliary movement, too little periciliary fluid 

   
• 3)  Gel or sputum layer 

  On the top where the cilia hooks into 

   

  Sticky mucus onto of the cilia will trap foreign materials and then the cilia will sweep the trapped particles out of the lungs 

  Buildup of mucus on the carina there will be a cough to try expel the material 

   

  Sputum  

  Cough Reflex 
• Ciliary movement and structure: 

  Some diseases can impair ciliary movement, ie someone with cystic fibrosus  

  Mucus becomes trapped and can't get cleared as easily 

   

  Movement of cilia is bidirectional, which can have a power stroke where the cilia hooks onto the mucus and moves it towards the mouth. Recovery stroke is when the cilia whips back around to try and get ready for the next hook of mucus.  
• Impaired mucociliary clearance: 

  • Dyskinetic cilia – abnormal movement of cilia 
  • Fluid balance  
  • Cold air – reduced ciliary beat frequency 
  • Hypersecretory conditions  
  • Post general anaesthesia  
  • Increasing age - reduced ciliary beat frequency, more structural anomalies 
  • Infection & inflammation 
  • Smoking – akinesias where the cilia stops moving, and the cilia gets burnt off which causes a buildup of sputum in the lungs. The irritants will cause more mucus from goblet cells but less cilia to clear it 

   
• Consequences of impaired MCT:  

  • Retention of secretions  
  • Potential microbial breeding culture 
  • Increased sputum production  
  • Airway obstruction  

  --> increased resistance & work of breathing  

  --> inadequate ventilation and hypoxaemia, low o2 in the blood 

  • Breathlessness 
• Wandering macrophages: 

  • Another lung defence mechanism  
  • At alveolar level  
  • Keep the alveolar surfaces sterile  
  • Dead macrophages swept up by cilia 
• Collateral ventilation: 

   

  Collateral channels 

  • Channels of Lambert  - bronchioles to alveoli 
  • Channels of Martin – between 2 bronchioles 
  • Pores of Kohn - alveolar septa have small fenestrations that provide communications between neighboring alveoli 

   
• When we breathe at rest there is no airflow through the collateral channels as it is much harder for air to get through it. 

  To increase airflow though collateral channels a deep breath will open the collateral channels. 

  Alveoli may collapse if no air gets to it,