Chapter 23:
Anatomy and Physiology of the
Respiratory System
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Thoracic Contents
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Posterior Thoracic Cage
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Anterior Thoracic Cage
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Frontal Section of the Chest
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Inspiration and Expiration
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Structures of the Respiratory System
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
The Human Airways
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Cast of the Airways of the Lung
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Anatomical Dead Space
Conducting airways have no alveoli and no gas exchange
occurs.
• Volume in this space is 150 mL.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Role of Surfactant in the Lungs
• Surfactant is a complex of lipoproteins that line the
alveoli and reduce surface tension across the air and
liquid interface in the alveoli.
• It helps to keep alveoli open and participating in gas
exchange.
• It helps to keep the alveoli dry to prevent pulmonary
edema.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Lobule of the Lung
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Circulation From Right Heart to Lungs and
Left Heart
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Anatomical Shunt in the Bronchial
Circulation
• No gas exchange occurs in the bronchial circuit.
• The blood in the pulmonary vein is unoxygenated; this
blood mixes with the oxygenated blood from the left side
of the heart.
• Reason why the SaO2 is <100% on room air
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Partitioning of Respiratory Pressures
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Phases of Ventilation
See Figure 23-12.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Fick’s Law
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
How Disease Process Affects AlveolarCapillary Gas Exchange
• Decrease in lung tissue means less surface area is
available for gas exchange.
• Thicker alveolar-capillary membrane leads to decreased
gas exchange.
• High altitudes or decrease in partial pressure of inspired
air decreases gas exchange.
• The solubility and molecular weight of gases determine
the ease of diffusion across the alveolar-capillary
membrane.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Normal Distribution of Ventilation
Depends on Body Position
• Sit/stand: ventilate best in lower zones
• Supine: apex and base ventilate same; posterior lung >
anterior lung
• Prone: anterior lung > posterior lung
• Lateral: dependent lung ventilates the best
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Explanation of Uneven Distribution of
Blood Flow
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Ventilation-Perfusion Situations
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
In a client with pneumonia, which of the following
ventilation-perfusion mismatches exists?
A. Alveolar dead space
B. Physiological shunt
C. Silent unit
D. Anatomical shunt
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
B. Physiological shunt
Rationale: A physiological shunt (low ventilation-perfusion
ratio) exists with pneumonia; the perfusion to the
alveoli is adequate, but the gas exchange is not. An
alveolar dead space (high ventilation-perfusion ratio)
occurs in pulmonary embolus: the alveoli are getting
adequate air exchange, but there is inadequate
perfusion of blood to the alveoli. Silent unit can happen
in a pneumothorax: both ventilation and perfusion are
decreased. An anatomical shunt occurs with congenital
heart disease.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Oxyhemoglobin Dissociation Curve
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
Respiratory acidosis causes the oxyhemoglobin dissociation
curve to shift to the:
A. Right, a decreased affinity of Hgb for O2 and an
increased release of O2 to tissues
B. Left, a decreased affinity of Hgb for O2 and an increased
release of O2 to tissues
C. Right, an increased affinity of Hgb for O2 and a
decreased release of O2 to tissues
D. Left, an increased affinity of Hgb for O2 and a decreased
release of O2 to tissues
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
A. Right, a decreased affinity of Hgb for O2 and an
increased release of O2 to tissues.
Rationale: Hemoglobin binds less readily with oxygen when
there is a decreased pH, increased CO2, elevated body
temperature, and elevated 2,3-DPG. This results in a
shift to the right of the oxyhemoglobin dissociation
curve and a decreased affinity of hemoglobin for oxygen
and an increased release of oxygen to tissues. A shift to
the left of the curve would result in the opposite effects.
Causes of a left shift include an increased pH, decreased
CO2, and hypothermia.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
When the central chemoreceptors are activated, the client
would:
A. Increase the rate and depth of respirations to inhale
more oxygen
B. Decrease the rate and depth of respirations to retain
more CO2
C. Hypoventilate to blow off retained CO2
D. Hyperventilate to blow off retained CO2
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
D. Hyperventilate to blow off retained CO2
Rationale: Central chemoreceptors are activated to get rid
of retained CO2 by hyperventilation to blow off the
excess CO2. Peripheral chemoreceptors are activated
when there is a low oxygen tension; this results in an
increased rate and depth to get more oxygen into the
system.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins