A&P Section 20- Impediments to Breathing

1. non-elastic resistance2. friction produced btw gas molecules and walls of airways3. 80%4. tissue resistance which relates primarily to disease conditions (ex fibrosis)5. when there is mvmt of air in resp tract--> therefore, only occurs during inspiration and expiration

1. sizea. radius2. Resistance is directly proportional to the viscosity of a fluid and the length of the tube through which it flows-- it is inversely proportional to the 4th power of the radius of the tube
R= (constant)(viscosity of fluid)(length) / (pie)(radius⁴⁾

1. resistance is increased by a factor of 162. airway resistance decreases as one descends the tracheobronchial tree3. smallest airways are very numerous compared to larger airways-- total SA of bronchioles is very large as compared to the totally surface area of trachea and bronchi-- total radii of the summed bronchioles is greater than the total radii of the summed trachea and bronchi4. slower air flow

- laminar- turbulent- transitional

1. smooth, streamlined flow2. concentric cylinders3. air molecules flowing next to wall of tube encounter more resistance d/t friction as compared to air flowing toward center of tube** cylinders more centrally located have faster flow rate4. occurs in tube-like airways

1. increased resistance d/t gas molecules encountering friction against airway walls2. occurs largely in nasal cavities in region of turbinates and also in the nasopharynx3. combination of laminar and turbulent flow4. seen at bifurcations (carina)

1. Velocity of air flow- incr velocity incr chance of turbulent airflow --> directly proportional2. diameter of tube- incr diameter incr chance of turbulence --> direct proportion3. viscosity= tendency for incr molecular friction btw gas molecules, causing them to "stick together"-- dcrs viscosity = incr chance of turbulence--> inverse relationship (incr viscosity --> less interaction btw molecules)4. density = incr density causes incr chance of turbulence --> directly proportional(more gas molecules/ unit volume= incr frictional contact with walls of tube)

1. Reynold's number (dimensionless number)2. Reynold's #= (density)(velocity)(diameter) / viscosity3. <2000 = flow is laminar2000-4000= flow is transitional (mixture of laminar and turbulent)> 4000 = turbulent

1. resistance to flow dcrs but chance of turbulence increases which increases resistance2. small airways3. the likelihood of air flow to change from laminar to turbulent

1. incr RR (30 breaths/ min) increases airway resistance d/t turbulent air flow2. the greater the depth of inspiration, the lesser the airway resistance-- b/c deeper inspirations cause enlargement of lungs and smaller airways3. increases airway resistance-- lungs dcrs in vol/ size; diameter of airways dcrs (elastic force)--> airway resistance increases

1a. increases airway resistanceb. lungs dcrs vol and size; airways dcrs diameter --> airway resistance increased to a greater extent as compared to a normal passive expiration-- increased IPP causes compression on small airways that have little or no cartilaginous support

1. -5cm H2O2. -8cm H2O3. throughout the lungs, outside the airways4. it helps to keep the alveoli distended by opposing the inward alveolar elastic recoil forces/ surface tension forces

1. +10 (includes surface tension and elastic)2. recoil - IPP10 - 8= 2cm H2O-- alveolar or intrapulmonic pressure-- pressure gradient for air to flow out of lungs (2cm H2O above ambient pressure)

1. pressure gradient2. to the outside d/t friction of gas molecules encountering decreased diameter of lower airway walls (increased airway resistance)

1. IPP increases to +25 d/t contraction of expiratory muscles (internal intercostals and abdominal)2. throughout the lungs (outside of airways)3. IPP= 25, alveolar recoil pressure= 10net alveolar pressure= 35cm H2O (pressure in the airway- inside alveoli)4. higher pressure gradient from alveoli to outside