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 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 DiseaseCaused by lack of surfactant due to prematurity 28 weeks of gestation is considered