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Structure and Function of the Pulmonary SystemChapter 32

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Structures of the Pulmonary System Airways Blood vessels Chest wall Lungs

Lobes Segments Lobules

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Structures of the Pulmonary System

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Structures of the Pulmonary System Conducting airways

Upper airways Nasopharynx Oropharynx

Larynx Connects upper and lower airways

Lower airways Trachea Bronchi Terminal bronchioles

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Structures of the Pulmonary System

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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

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Structures of the Pulmonary System

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Structures of the Pulmonary System

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Structures of the Pulmonary System

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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

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Pulmonary and Bronchial Circulation

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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

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Pulmonary and Bronchial Circulation

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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

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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

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Ventilation Neurochemical control

Respiratory center Dorsal respiratory group Ventral respiratory group Pneumotaxic center Apneustic center

Peripheral chemoreceptors

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Ventilation Neurochemical control

Lung receptors Irritant receptors Stretch receptors J-receptors

Chemoreceptors Central chemoreceptors Peripheral chemoreceptors

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Mechanics of Breathing Major and accessory muscles

Major muscles of inspiration Diaphragm External intercostals

Accessory muscles of inspiration Sternocleidomastoid and scalene muscles

Accessory muscles of expiration Abdominal and internal intercostal muscles

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Muscles of Ventilation

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Mechanics of Breathing Alveolar surface tension

Function of surfactant Elastic properties of the lung and chest wall

Elastic recoil Compliance

Airway resistance Work of breathing

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Mechanics of Breathing

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Measurement of Gas Pressure Barometric pressure

Partial pressure Partial pressure of water vapor

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Measurement of Gas Pressure

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Measurement of Gas Pressure

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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

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Gas Transport Distribution of ventilation and perfusion

Gravity and alveolar pressure Ventilation-perfusion ratio

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Measurement of Gas Pressure

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Gas Transport Oxygen transport

Diffusion across the alveolocapillary membrane Determinants of arterial oxygenation Oxyhemoglobin association and dissociation

Oxyhemoglobin dissociation curve

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Measurement of Gas Pressure

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Gas Transport Carbon dioxide transport

Dissolved in plasma Bicarbonate Carbamino compounds

Haldane effect

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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

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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

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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

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Aging and the Pulmonary System