IV. Respiratory Physiology
A. Purpose is to supply body and cells with oxygen and remove CO2
produced through cellular activities
B. Pulmonary Ventilation - Processes involved:
http://www.emptynosesyndrome.org/pics/image-res003.jpg
1. INSPIRATION
a. Occurs when alveolar pressure falls below atmospheric
pressure
b. Contraction of the diaphragm and external intercostal
muscles increase the volume in the thorax so the lungs expand
c. Expansion of the lungs decreases alveolar pressure so air
moves along the
pressure gradient from the atmosphere (high
pressure) into the lungs (low
pressure)
d. During forced inspiration accessory muscles of respiration
are used.
http://faculty.stcc.edu/AandP/AP/imagesAP2/respiration/inspire.jpg
2. EXPIRATION
a. Occurs when alveolar
pressure is higher in than
atmospheric pressure
b. Relaxation of the diaphragm
and intercostal muscles
decrease lung volumeso air
moves out of the lungs
c. Forced expiration involves
contraction of the internal
intercostal muscles and
abdominal muscles
d. A collapsed lung is caused by
air in the pleural cavities,
airway blockage or a lack of
surfactant
e. Average respirations =
12/min at rest
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http://www.nlm.nih.gov/medlineplus/en
cy/images/ency/fullsize/19589.jpg
http://images.emedicinehealth.com/images/eMedicineH
ealth/illustrations/pneumothorax.jpg
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V. Pulmonary Air Volumes and Capacities
A. Pulmonary Volumes
1. TIDAL VOLUME -Volume of air inspired or expired. (Average
tidal volume = 500 mL )
2. IRV – Inspiratory Reserve Volume – Excess air inhaled during
a deep breath (3100 mL above tidal volume)
3. ERV – Expiratory Reserve Volume – the excess air that can be
forced out after a normal inhalation (1200mL)
4. MINIMAL VOLUME – the air remaining after the thoracic
cavity is opened and the pressure balances, forces out excess
volume
Provides a medical and legal tool for determining the time of
death of a newborn (before or after birth)
B. Lung Capacities
1. IC - Inspiratory Capacity – total inspiratory ability of the
lungs following a normal expiration
2. FRC – Functional Residual Capacity – the volume of air
remaining in lungs after a normal expiration
3. VITAL CAPACITY – the maximum amount of air that can be
expired following maximum inpiration
4. TLC – Total Lung Capacity – the maximum amount of air in
the lungs following maximal inspiration (sum of all volumes)
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VI. Gas Exchange
A. Partial Pressure (p)
1. The pressure exerted by a gas in a mixture of gases.
2. Each gas in a mixture exerts its own pressure; it behave as
if it were alone.
B. External (pulmonary) Respiration
1. Movement of O2 and CO2 between alveoli of the lungs and
the pulmonary area where partial pressure is lower.
2. Each has moves independently
3. High altitude sickness results from lower pO2 so less O2
diffuses into the blood
C. Internal (tissue) Respiration
1. Movement of O2 and CO2 between tissues capillaries and
tissue cells.
2. O2 and CO2 exchange as a result of difference of p of O2
and CO2
3. Cells are producing CO2 as a result of cell processes
Gas exchange animation
http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapter44/animations.
html#
D. Transport
1. Most oxygen is carried by the iron
atoms in the heme of the
hemoglobin
2. CO combines with hemoglobin
much like oxygen but the
combination is 200 times stronger
3. HYPOXIA – deficiency of oxygen at
the tissue level.
http://www.nlm.nih.gov/medlinep
lus/ency/images/ency/fullsize/1951
0.jpg
4. CO2 is transported in plasm,
combines with globin and 70% is
converted to bicarbonate ions
(HCO31-)
http://www.buteyko.eu/hemoglobinOK.JPG
VII. Control
A. Nervous Control – The
respiratory center consists of
the medullary rhythmicity
area, the pneumotaxic area
and the apneustic area.
1. Medullary sets the rhythm
2. Pneumotaxic and apneustic
coordinate inspiration and
expiration.
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