Lecture notes
Respiratory system summary (Pam lecture)
- Module
- Physiolgy (PHOL0001)
- Institution
- University College London (UCL)
It includes all the lecture notes about respiratory system in module PHOL0001
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Lecture 1 structure and function of Respiratory system● Major features
- 23 generations of airways between the atmosphere and the alveoli.
- ~ 17 million branches
- ~ 300 million alveoli and 60-80 m2 surface area.
Nasal cavity (ideal, as it moisture the air) / mouth (heavy breathing)
Trachea - 8 cm in diameter and 12 cm in length, generation 0
Two main primary bronchi - right bronchi (3 lobes of lung) > left bronchi (2 lobes),
generation 1
Secondary bronchus
Tertiary bronchus
Bronchioles - 12-16 generation
Respiratory bronchioles - 17-19 generation
Alveoli - 23 generation, 300 million
● Alveolar-capillary unit
- each of which is almost completely enveloped by pulmonary capillaries
- thin alveolar epithelial layer consist 2 types of cells:
Type I - squamous epithelial cells
Type II - thicker and produce pulmonary surfactant
- pulmonary capillaries lined the alveoli, capillary endothelial cells contain red
blood cell for gas exchange, very little interstitial space between alveolar
epithelial cell and endothelial cell.
,Boyle’s law
● describes the relationship between volume and pressure in a gas at a constant
temperature.
Pressure is inversely proportional to volume.
● Ventilation depends on 3 types of pressure:
- Atmospheric
- Intra-alveolar (inside alveoli)
- Intrapleural (inside chest cavity, sealed)
● inspiration
Atmospheric pressure > intrapleural pressure
Air flows inside the chest cavity due to pressure.
Chest cavity (Thoracic volume) increases:
- diaphragm contracts and descends.
- External intercostal muscles contract and lift the chest wall up and outward.
- Scalenes (accessory muscles) contract to lift the chest further for heavy
inspiration
● Expiration (active process)
Alveolar pressure > atmospheric pressure
Air flows out of the chest due to pressure.
Thoracic volume decreases:
- Internal intercostal muscle contract
- abdominal muscles contract
, Pressure changes during respiratory cycle
Blue line - tidal air
Green line - alveolar pressure
Red line - intrapleural pressure
Dotted line - atmospheric pressure
Inspiration
- Atmospheric pressure > alveolar pressure ⇒ air flow inside chest down a pressure
gradient
- Intrapleural pressure DECREASES as the thoracic volume increases.
Expiration
- Alveolar pressure > atmospheric pressure ⇒ air flow out of the chest
- Intrapleural pressure INCREASES as the thoracic volume decreases.
Lung compliance
- The change in chest volume due to a given change in intrapleural pressure. (How
difficult it is to expand the chest)
C (Compliance) = ▵V / ▵P
Compliance = L/cmH2O or L/kPa
healthy compliance = 1.01 L / kPa or (0.11 L / cmH2O)
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