DEFENSE MECHANISM OF LUNG| Tutorial B-1 RS130110110177|Gabriella Chafrina| 29/11/13Function: to protect itself against potentially toxic inhaled material Have major categories: 1)Physical/ Anatomic factors and Functional factors Function: deposition and clearance inhaled materials -Anatomic factors/def enses oFunction: promote deposition of particles in upper airways prevents the majority inhaled particles from reaching alveoli oDeterminant: Particle size >10 um: settle in nose 5 um–10 um: settle in trachea, conducting airways <5 um: reach distal lung parenchyma many bacteria in this size range so that deposition along airways not very effective for excluding bacteria from the LRT Inspiratory flow rate ↑ in velocity of inspiratory flow promotes deposition of particles by impaction in upper airways -Functional factors/def enses oFunction: promote clearance of particles through actions, such as: Cough Is important protective mechanism, frequently triggered by stimulation if air way irritant receptors that are activated by inhaled or aspirated fore ign material Receptors fo und in larynx, trachea, and major bronchi. More common at point of bifurcation Afferent: vagus, trigeminal, and glossopharyngeal nerves Effere nt: recurrent pharyngeal nerve (a branch of vagus control glottis, phrenic, and spinal nerves contract diaphgram and expiratory muscles of chest and abdominal walls) Mucociliary transport/clearance Is a process of waves of beating cilia moving a blanket of mucus (and any material trapped within the mucus) progressively upward along the tracheobronchi al tree From trachea down to respiratory bronchioles, has cilia projecting into airway lumen Cilia: beat in coordinated manner, frequencies between 600-900 beats/min, speed 6-20 mm/min when do ciliary beating (to remove debris deposited on mucous blanket), have structure identical to cilia found elsewhere in body Ciliary beating: move a blanket of mucus in cephalad direction (i.e: from distal to more proximal parts of tracheobronchial tree) Mucous blanket: there are 2 layers comprise: Sol layer Located adjacent to cilia Origin unknown Gel layer Located at the luminal surface Consists of complex polymer of mucopolysaccharides, produced by goblet and mucus-secreting cells More viscous Cough and mucociliary transport is happening when particles deposited in trachea or bronchi, but when it deposit in alveoli, cellular defense will take control
