The Respiratory System - Lab
The main function of the respiratory system is to
supply oxygen to, & eliminate carbon dioxide
from the body
In order to accomplish this task, the respiratory
system must work in conjunction with the
cardiovascular system
Anatomy Overview
Nasal cavity
Pharynx
Larynx
Trachea
Bronchi
The respiratory tract includes:
Nose (nasal cavity) Pharynx
(nasopharynx, oropharynx,
laryngopharynx) Larynx
Trachea Bronchi (primary,
secondary (lobar), tertiary
(segmental)) Bronchioles
Terminal bronchioles Alveolar
ducts Alveoli
Bronchioles
Respiratory
bronchioles
Right
Lung
Left
Lung
Alveolar duct
Alveoli
“Respiration” refers to the overall exchange of
gases between the atmosphere, blood & cells
Respiration involves 3 processes
 Pulmonary ventilation
 Gas exchange (gas diffusion)
 External respiration
 Internal respiration
 Gas transport
Physiology of Respiration
Pulmonary Ventilation – “exchange” (movement) of gases
between the atmosphere & lungs; movement of gases
occurs because of pressure differences between the
atmosphere (atmospheric pressure (Po)) & lungs
(intrapulmonic pressure (Pi))
Two phases of ventilation:
 Inspiration (inhalation)
Expiration (exhalation)
Po at sea level =
760 mmHg
Pulmonary Ventilation - Inspiration
Inspiration (inhalation) Active process involving contraction of diaphragm &
external intercostal muscles
Contraction of diaphragm
& external intercostal
muscles  increased
volume of thoracic cavity
 tension on parietal &
visceral pleura 
increased volume of
lungs  decreased
intrapulmonic pressure 
air flows in
Pulmonary Ventilation - Expiration
Expiration (exhalation) • normally passive due to relaxation
of diaphragm & external intercostal
muscles
• can be made active (forced
expiration) due to contraction of
abdominals & internal intercostal
muscles
Relaxation of diaphagm/external intercostals 
decreased volume of thoracic cavity  decreased
lung volume  increased intrapulmonic pressure
 air flows out
Gas Exchange (gas diffusion)
 External respiration - the diffusion of O2 & CO2 between the alveoli &
blood across the respiratory membrane
 occurs because of pressure differences of each gas within alveolar
air & pulmonary (deoxygenated) blood
 results in creation of oxygenated blood
Gas Exchange
 Internal respiration – the diffusion of O2 & CO2 between the blood
& interstitial fluid across the endothelium of systemic capillaries
 occurs because of pressure differences of each gas between
systemic (oxygenated) blood & interstitial fluid
 results in creation of deoxygenated blood
Lung Volumes & Capacities
 Respiratory frequency (f) – number of ventilations
(inspiration+expiration) per minute. (12-20 breaths/min)
 Tidal volume (TV) - amount of air moved in or out of the
lungs during a normal breath (500 ml)
 Minute ventilation (VE=TV x f)- amount of air inhaled or
exhaled in one minute (6000 ml/min)
Lung Volumes & Capacities (cont.)
 Inspiratory reserve volume (IRV) – amount of air that
can be inhaled after a normal inspiration (above the resting
TV) (2500ml/1900ml)
 Inspiratory capacity (IC = TV+IRV) – amount of air
inhaled after a normal expiration (3000ml/2400ml)
Lung Volumes & Capacities (cont.)
 Expiratory reserve volume (ERV) – amount of air that
can be exhaled after a normal expiration (1000ml/700ml)
 Residual volume (RV) – amount of air remaining in
lungs even after maximal expiration (1200ml/1100ml avg –
25% of VC)
 Vital capacity (VC=TV+IRV+ERV) – maximum amount of
air you can exhale, following a maximal inhalation
(4000ml/3100ml)
 Total lung capacity (TLC=TV+IRV+ERV+RV) –
maximum amount of air in your lungs, following a maximal
inhalation (5200ml/4200ml)
Control of Respiration
Unconscious control of breathing occurs through the activity of the
respiratory centers of the brain
 Medulla oblongata – “Rhythmicity center” controls basic pattern of
breathing; inhale 2 seconds, exhale 3 seconds
 Pons – has 2 centers (apneustic & pneumotaxic centers) that can
unconsciously modify the rate & depth of respiration
Respiratory centers can be influenced by
mechanoreceptors (i.e. stretch receptors
in lungs) & chemoreceptors (sensitive to
CO2 levels, arterial pH, & O2 levels) in the
body, as well as by higher brain centers