Structure and Function of
the Pulmonary System
Chapter 32
1
Structures of the Pulmonary
System




Airways
Blood vessels
Chest wall
Lungs



Lobes
Segments
Lobules
2
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Structures of the Pulmonary
System
3
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Structures of the Pulmonary
System

Conducting airways

Upper airways



Larynx


Nasopharynx
Oropharynx
Connects upper and lower airways
Lower airways



Trachea
Bronchi
Terminal bronchioles
4
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Structures of the Pulmonary
System
5
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Structures of the Pulmonary
System

Gas-exchange airways



Respiratory bronchioles
Alveolar ducts
Alveoli

Epithelial cells


Type I alveolar cells

Alveolar structure
Type II alveolar cells

Surfactant production
6
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Structures of the Pulmonary
System
7
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Structures of the Pulmonary
System
8
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Structures of the Pulmonary
System
9
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Pulmonary and Bronchial
Circulation




Pulmonary circulation has a lower pressure
than the systemic circulation
One third of pulmonary vessels are filled with
blood at any given time
Pulmonary artery divides and enters the lung
at the hilus
Each bronchus and bronchiole has an
accompanying artery or arteriole
10
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Pulmonary and Bronchial
Circulation
11
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Pulmonary and Bronchial
Circulation

Alveolocapillary membrane


Formed by the shared alveolar and capillary walls
Thin membrane of alveolar epithelium, the
alveolar basement membrane, interstitial space,
the capillary basement membrane, and the
capillary endothelium
12
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Pulmonary and Bronchial
Circulation
13
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Chest Wall and Pleura

Chest wall



Skin, ribs, and intercostal muscles
Thoracic cavity
Pleura




Serous membrane
Parietal and visceral layers
Pleural space (cavity)
Pleural fluid
14
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Function of the Pulmonary System

Ventilation


Mechanical movement of gas or air into and out
of the lungs
Minute volume


Ventilatory rate multiplied by the volume of air per
breath
Alveolar ventilation
15
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Ventilation

Neurochemical control

Respiratory center





Dorsal respiratory group
Ventral respiratory group
Pneumotaxic center
Apneustic center
Peripheral chemoreceptors
16
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Ventilation

Neurochemical control

Lung receptors




Irritant receptors
Stretch receptors
J-receptors
Chemoreceptors


Central chemoreceptors
Peripheral chemoreceptors
17
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Mechanics of Breathing

Major and accessory muscles

Major muscles of inspiration



Accessory muscles of inspiration


Diaphragm
External intercostals
Sternocleidomastoid and scalene muscles
Accessory muscles of expiration

Abdominal and internal intercostal muscles
18
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Muscles of Ventilation
19
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Mechanics of Breathing

Alveolar surface tension


Elastic properties of the lung and chest wall




Function of surfactant
Elastic recoil
Compliance
Airway resistance
Work of breathing
20
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Mechanics of Breathing
21
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Measurement of Gas Pressure

Barometric pressure


Partial pressure
Partial pressure of water vapor
22
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Measurement of Gas Pressure
23
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Measurement of Gas Pressure
24
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Gas Transport

Four steps





Ventilation of the lungs
Diffusion of oxygen from the alveoli into the
capillary blood
Perfusion of systemic capillaries with oxygenated
blood
Diffusion of oxygen from systemic capillaries
into the cells
Diffusion of CO2 occurs in reverse order
25
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Gas Transport

Distribution of ventilation and perfusion


Gravity and alveolar pressure
Ventilation-perfusion ratio
26
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Measurement of Gas Pressure
27
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Gas Transport

Oxygen transport



Diffusion across the alveolocapillary membrane
Determinants of arterial oxygenation
Oxyhemoglobin association and dissociation

Oxyhemoglobin dissociation curve
28
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Measurement of Gas Pressure
29
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Gas Transport

Carbon dioxide transport




Dissolved in plasma
Bicarbonate
Carbamino compounds
Haldane effect
30
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Control of Pulmonary Circulation

Hypoxic vasoconstriction


Caused by low alveolar pO2
Blood is shunted to other, well-ventilated portions
of the lungs



Provides better ventilation and perfusion matching
If hypoxia affects all segments of the lungs, the
vasoconstriction can result in pulmonary hypertension
Acidemia also causes pulmonary artery
constriction
31
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Tests of Pulmonary Function







Spirometry
Diffusion capacity
Residual volume
Functional reserve capacity (FRC)
Total lung capacity
Arterial blood gas analysis
Chest radiographs
32
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Aging and the Pulmonary System




Loss of elastic recoil
Stiffening of the chest wall
Alterations in gas exchange
Increases in flow resistance
33
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Aging and the Pulmonary System
34
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