The Respiratory system. Pulmonary ventilation – Chp 16 Respiration. Outline. Overview of the respiratory system Anatomy Forces for pulmonary ventilation Factors affecting pulmonary ventilation Clinical significance of respiratory volumes and air flows. Outline.
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Respiration = gas exchange -- Occurs at the levels of the lungs and tissues (external respiration) and cell (internal or cellular respiration).
- Pulmonary ventilation: movement of air in and out
of the lungs
Gas exchange in the alveoli
Gas transport in the blood
Gas exchanges between blood and tissues
- nose to pharynx
- Conducting airway:
- Respiratory airway:
Due to the wall structure of the airway: one cell layer (SSE) allows for gas exchange
Presence of cartilage in the wall, from larynx to small bronchi prevents airway collapse.
Goblet cells secreted mucus. Ciliated cells help move the mucus out of the airway.
Presence of smooth muscle fibers in the bronchioles (but no cartilage)
Volume of the conducting airway: 150 ml
Type I cells gas exchange
Type II cells secrete surfactant (lipoproteins) decrease surface tension allowing for easier alveoli inflation
Surfactants start to be secreted by the 7th month of pregnancy risk of lung disease in premature babies
Presence of macrophages in alveoli
Formed by 2 layers: the parietal and visceral pleura
- prevents friction of the lungs against the rib cage (due to the thin layer of liquid present in the pleural space)
- maintains lung expansion: due to the negative pressure within the pleural space
What is negative pressure? What is its importance?
Pneumothorax: lung collapse due to air entering in the pleural cavity
(not to be confused with atelectasy alveoli collapse)
Boyle’s law: The pressure of a gas in a closed container is inversely proportional to the volume of the container.
Air flow in the lungs is driven by the differences in pressure between the atmosphere and the alveoli
P.atm is constant changes in P.alv drive ventilation
Inspiration: chest wall expands due to muscle contraction (diaphragm and/or other muscles)
Pressure in alveoli ↓ air moves toward alveoli
Expiration: passive process muscle relax chest wall return to resting state alveoli become compressed ↑ alveolar pressure move moves out
1- Lung compliance: ease with which lungs can be stretched
- Compliance is a measure of the elasticity of lung tissue and the alveolar surface tension
2- Airway resistance: to changes in airway radius (↓radius ↑resistance)
lung disease resulting in stiffness of tissue
no or ↓ surfactant
Can help distinguish between obstructive pulmonary disease and restrictive pulmonary disease
Obstructive disease: obstruction in bronchi-bronchioles severely restricts the speed and amount of air movement
Damage to lung tissue prevents full lung expansion and recoil
Anatomical dead space: space within the conductive airway, about 150 ml.
What will happen to a person who has a tidal volume of 150 ml due to lung disease?
What can be done to help the person?