Mechanics of breathing.

  

Mechanics of breathing. 

**Mechanics [i.e. process] of breathing, or pulmonary ventilation consists of two phases:  *Inspiration (Air in-flow), & *Expiration (Air out-flow)..

Subtitle: Pressure Relationships in thoracic cavity: Breathing process has respiratory pressure that occur in thoracic cavity, & these respiratory pressures are always relative to atmospheric pressure(P atm)…which is the pressure exerted by the air surrounding the body.** & (it is 760mmHg) And described as: * A negative respiratory pressure..{i.e. a pressure in any respiratory area (within the thoracic cavity) that is lower than atmospheric pressure  by “4mmHg” such as: (760mmHg – 4 =756mmHg) *and a positive pressure which is equal to amtospheric pressure, so called: Zero respiratory pressure…**which are all about: Intrapulmonary pressure & intrapleural pressure.. **The intrapulmonary(i.e. intra alveolar) pressure..{Ppul} is the pressure in the alveoli & always equalizes with (Patm) **NB: Ppul rises and falls with breathing phases.        ******AS FIG- 21.12 shows…….

*Whereas, Intrapleural pressure: ( Pip) Is a pressure in the pleural cavity, & is always less “4mmHg” than intrapulmonary pressure....[i.e, Pip is negative to Ppul]..

**thereby, the difference between intrapulmonary & intrapleural pressures, so called: transpulmonary pressure, Keeps the lungs open or from collapsing..

  i.e. It is a dynamic constancy in thoracic cavity, *& it is a corrective  method of *ventilation Because of, Pulmonary ventilation depends on *Volume changes in thoracic cavity..

And volume changes lead to *pressure changes, and then lead to flow of gases