respiratory
Pulmonary System
Essentials of Exercise Physiology
respiratory
Respiration


External respiration: ventilation and exchange of
gasses in the lungs (pulmonary function).
Internal respiration: ventilation and exchange of
gasses in the tissues (pulmonary function).
respiratory
Functions of Respiratory System
Primary purpose of
respiratory system is:
Provide means of oxygen
exchange between external
environment and body
Provide a means of carbon
dioxide exchange between
the body and the external
environment
Exchange occurs as result:
Ventilation: mechanical
Diffusion: random movement
respiratory
Functions of Respiratory System
Respiratory system also
helps regulate acid-base
balance in body,
especially during
exercise.
Cl- + H+ + NaHCO3 
NaCl + H2CO3 
CO2 + H2O
respiratory
Acid - Base Balance

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Acids - molecules which can liberate
hydrogen ions
Bases - molecules which can accept hydrogen
ions
Buffer - resists changes in pH by either
accepting hydrogen ions or liberating them
depending upon local conditions
respiratory
Structure Pulmonary System

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Right and left lungs enclosed by membranes
called pleura
Visceral pleura adheres to outer surface of
lungs
Parietal pleura adheres to thoracic wall and
diaphragm
respiratory
respiratory
Intrapleural Space

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Contains fluid which
lubricates pleura
Creates a low pressure
area
– pressure is below
atmospheric during
inspiration, allowing the
lungs to inflate
respiratory
Functional Zones
of Air Passages

Conducting zone
– passageways leading to respiratory zone
– area where no gas exchange occurs
– nasal cavity, pharynx, larynx, trachea, bronchioles

Respiratory zone
– where gas exchange actually occurs
– alveoli
respiratory
Roles of Conducting Zone

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Warms air
Mucus traps small particles
Cilia sweep particles upwards
Macrophages engulf foreign particles
respiratory
Roles of Respiratory Zone

Provides large surface area for gas exchange
– 600 million alveoli
– Total surface area is 60 – 80 square meters or
about size of half a tennis court

Provides a very thin barrier for gas exchange
– 2 cell layers thick
respiratory
Alveoli

Type II alveolar cells secrete pulmonary
surfactant
– form a monomolecular layer over alveolar
surfaces
– surfactant stabilizes alveolar volume by
reducing surface tension created by moisture
respiratory
Mechanics of Ventilation

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Change in thoracic cavity volume produces
corresponding change in lung volume
Increase in lung volume results in decrease in
lung pressure (Boyle’s law)
Differences in pressure pulls air into the lungs
– pressure within the lungs becomes less than the
atmospheric pressure
– bulk flow (from high pressure to low pressure)
respiratory
Muscles of Inspiration

Diaphragm
– contracts, flattens, & moves downward up to 10 cm
– enlarges & elongates chest cavity, expands volume
– during quiet breathing diaphragm works alone

External intercostals, pectoralis minor,
sternocleidomastoid & scaleni
– lift ribs up and outwards
– during exercise, accessory muscles called into play
respiratory
Muscles of Inspiration
respiratory
Muscles of Expiration

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Expiration during quiet breathing is passive
due to elastic recoil of chest cavity
Decrease in lung volume forces air out of
lungs
During exercise and voluntary
hyperventilation,
– rectus abdominus, transverse abdominus: push
diaphragm up
– internal intercostals: pull ribs downwards
respiratory
Total Lung Capacity

Tidal volume (VT)
– amount either inspired or expired during normal
ventilation

Inspiratory reserve volume
– maximal volume inspired after a normal inspiration

Expiratory reserve volume
– volume expired after a normal expiration

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During exercise VT increases largely from IRV.
Residual volume
– volume remaining in lungs after maximal expiration
respiratory
Lung Capacities

Total lung capacity
– volume within lung after a maximal inspiration

Inspiratory capacity
– maximal volume inspired from the end of tidal
expiration

Functional residual capacity
– volume in lungs after normal expiration

Vital capacity
– maximal volume expired after maximal inspiration
respiratory
Dynamic Lung Volumes

Depend on volume and speed of air movement;
more useful in diagnosing lung disease.

FEV: Forced Expiratory Volume. Volume that
can be forcefully expired after maximal
inspiration within given time, usually 1 sec.

MVV: Maximal Voluntary Ventilation. Volume
of air that can be ventilated by maximal effort in
one minute. Breathe maximally for 12 (or 15)
seconds and total volume recorded, multiplied by
five (or 4).
respiratory
respiratory
Minute Ventilation

Volume of gas ventilated in one minute
–
–
–
–
–
ERROR
equal to tidal volume times frequency
Rest in 70 kg man, 6.0 L/min = 0.5 L x 12
Maximal exercise, 120-175 L/m = 3-3.5 x 40-50
increases as oxygen consumption increases
closely associated with CO2 production
respiratory
Anatomical vs Physiological
Dead Space

Anatomical dead space
– areas of conducting zone not designed for
diffusion of gases
– VT = VA + VD
– At rest, VT = 500 ml = 350 ml + 150 ml

Physiological dead space
– areas of lung and pulmonary capillary bed which
are unable to perform gas exchange as designed
respiratory
Anatomic Dead Space
respiratory
Physiologic Dead Space
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Optimal diffusion requires matching of ventilation to
perfusion: 1 ventilated alveoli/ 1 blood perfused alveoli
Ventilation (V) / perfusion (Q) is not equal across the
lung
Top of lung is poorly perfused
– V / Q = 3.3 at top of lung
Bottom of lung has more perfusion than ventilation
– V / Q = .63 at bottom of lung
V / Q values above .5 are generally adequate
respiratory
Minute Ventilation in Exercise

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Adjustments in breathing rate and depth maintain
alveolar ventilation as exercise.
Trained athletes maintain alveolar ventilation by
increasing VT and minimal increase rate.
Deeper breathing causes a greater percentage of
incoming “fresh” VT to enter alveoli.
Increasing VT in exercise results from encroaching
primarily on IRV or ERV?
VT plateaus at about 60% vital capacity.
respiratory
Disruptions in Normal Breathing

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Dyspnea shortness of
breath or subjective
distress in breathing.
Hyperventilation ≠
Hyperpnea
Valsalva maneuver:
forced exhalation
against closed glottis.
What happens to blood
pressure?
respiratory
Gas Exchange
Fick’s Law


Diffusion occurs at a rate which is
proportional to differences in partial
pressure and the surface area available and
is inversely proportional to the thickness of
the membrane.
Diffusion rate = (P1 - P2) area
thickness