Ch 17 - Mechanics of breathing

respiratory functions

exchange of gases between the atmosphere and blood, homeostatic regulation of body pH, protection from inhaled pathogens and irritating substances, vocalization

4 processes of respiration

1. pulmonary ventilation (movement of air between env and lungs)

2. external respiration (exchange of gases between alveoli in lungs and bloodstream)

3. transport of respiratory gases

4. internal respiration (exchange of gases between blood and cells of body)

ways to divide respiratory system

structurally - upper vs lower

physiologically - conducting (ventilation) vs exchange (respiration)

airway branching in lower respiratory tract

conducting (filter and warm air) - trachea, primary bronchi, smaller bronchi, bronchioles

exchange - respiratory bronchioles, alveoli

alevoli

type 1 - very flat, simple squamous

type 2 - produce surfactant to reduce surface tension, helps hold walls out to prevent collapse

low pressure and low resistance allow high flow of gas exchange, flat cells make a thin barrier

pressures of lungs

atmospheric (P atm) - 760 mmHg

intrapleural (P ip, between lung/thoracic wall) - 756 mmHg

intrapulmonary (P pul, inside lungs) - 760 mmHg

transpulmonary - difference between P ip and P pul

ventilation requires on pressure changes

P atm=P pul no ventilation

P atm > P pul inhale

P atm < P pul exhale

P ip > P pul lung collapse

pulmonary ventilation musculature

inspiration causes diaphragm and external intercostals to contract (active), increase in volume in lungs, lowers pressure (pump hangle or bucket handle)

expiration relaxes diaphragm and external intercostals (passive), decrease in volume in lungs, increases pressure to push air out

pressures required for ventilation

inspiration - P pul 758, P ip 754

expiration - P pul 762, P ip 758

lung volumes

inspiratory reserve - additional volume you can inhale

tidal volume - normal air moving in breathing

expiratory reserve - exhale farther than normal

residual volume - always need some air in lungs, don't use for breathing

inspiratory capacity = tidal volume-inspiratory reserve

functional residual capacity = expiratory reserve-residual volume

air flow

flow goes from higher pressure to lower, muscular pump creates pressure gradients, resistance to air flow is influenced primarily by diameter of tubes, smooth muscle controls airway resistance (sympathetic reduces resistance, parasympathetic increases)

lung compliance vs elastic recoil

lung compliance - ability of lungs to stretch

elastic recoil - abiltiy to return to resting volume/push air out

emphysema vs fibrosis

emphysema - destroys alveoli walls so air is trapped in lungs, high compliance low elastic recoil

fibrosis - low compliance high elastic recoil, looks like you're getting lots out but not much gets in

forced vital capacity (FVC) test

look at FEV1 (expiratory flowrate after 1 second) and FVC (max expiratory rate, usually 4 seconds), percentage should be about 80% (normal is 4 and 5)

obstructive lung disease - ratio less than 80%, increased airway resistance decreases flow

restrictive lung disease - higher than 80%, reduced lung compliance