 Pulmonary ventilation: air is moved in and out of the lungs  External respiration: gas exchange between blood and alveoli  Respiratory gas transport: CV system transports oxygen and carbon dioxide between lungs & tissues (discussed in Blood chapter)  Internal respiration: gas exchange between blood & tissue cells  Definition: Cellular respiration: actual use of oxygen & production of carbon dioxide in the cells  (this is why we have to breathe!!)

 Pulmonary ventilation: - Moving air into and out of the lungs  Depends on pressure changes  Breathing  Inspiration = moving air into the lungs  Expiration = moving air out of lungs

 Intrapulmonary pressure  Pressure within the alveoli (lungs)  Changes with phases of breathing  Always equalizes itself with atmospheric pressure  Intrapleural pressure  Pressure within intrapleural space (between the pleural membranes )  Always 4 mmHg less than intrapulmonary pressure

 Any conditions that causes intrapulmonary pressure to equal intrapleural pressure will cause the lungs to collapse  This means they lose the ability to move air since there is NO more pressure difference

 term for lung collapse

 Air in the intrapleural space due to trauma – causes lung collapse

 Question: Why does breathing happen?  ONLY acceptable answer: The RULE: Volume changes lead to pressure changes which lead to the flow of gases to equalize the pressure

Boyle’s Law = Pressure & Volume have an INVERSE relationship.

 Main inspiratory muscles  Diaphragm & external intercostals  Thoracic dimensions change to increase volume of thoracic cavity by 0.5 liters  Intrapulmonary pressure drops 1-3 mmHg and air rushes info normal quiet inspiration  A deep forced (active) inspiration requires activation of accessory muscles – see diagram in notes

 A passive process dependent on natural lung elasticity  lungs recoil when inspiration stops – so alveoli compress –which leads to a volume  decreases -causing intrapulmonary pressure to rise - gas outflows to equalize the pressure with atmospheric pressure  Forced (active) expiration requires contraction of abdominals, etc – see diagram

 Bronchial sounds: produced by air rushing through trachea & bronchi  Vesicular sounds: produced by air filling alveoli

 Wheezing: whistling sound  Rales: rasping sound

 Basic Lung Sounds – Bronchial Basic Lung Sounds – Bronchial  Auscultating The Lungs - Reference Guide Auscultating The Lungs - Reference Guide

 Pulmonary ventilation can be influenced by 4 physical factors  Respiratory passage resistance  Lung compliance  Lung elasticity  Alveolar surface tension forces

 Resistance due to increased friction as air moves through passages  Smooth muscle bronchoconstriction Disorders such as asthma – when bronchi constrict  Local accumulations of mucus, infectious material, and tumors – also block air passage

 Condition where the bronchi become inflamed and begin to close down.  Causes individual to have trouble breathing, and if severe enough, may close down airways.

 The ease with which lungs can readily expand  Affected by the elasticity of the lungs and the thoracic cage which can be diminished by 2 main factors:  Fibrosis of the lung tissue  Ossification and/or muscle paralysis impairs flexibility of the thoracic cage

 Essential for normal expiration  Emphysema: tissue becomes less elastic and more fibrous  loss of elasticity & increase in fibrous tissue causes enormous effort to exhale – at end stages, alveolar walls break down and surface area is lost for gas exchange

 Surface tension is caused by the tendency of polar molecules such as water to stick to each other with hydrogen bonds  this can cause the walls of the alveoli to stick together like plastic wrap every time you exhale.  Large amounts of energy /effort will be required to simply re-expand the lungs and allow you to inhale

 Surfactant – interferes with cohesion of water molecules so less energy needed to expand lungs – this is one of the things that keeps our lungs partially expanded at all times. (the other thing is the pressure difference previously discussed)  Secreted by Type II cells in lungs

 AKA: Hyaline Membrane Disease  Caused by lack of surfactant due to prematurity  28 weeks of gestation is considered