Mechanics Of Breathing-1 Flashcards
What are the secondary functions of respiration ?
Acid-base balance Vocalisation Defence against pathogens Avenue for water and heat loss Enhancing venous return Activating some. Plasma proteins
What is the primary function of respiration ?
Gas exchange
What is internal respiration ?
Oxygen is essential for ATP production by oxidative phosphorylation
What is external respiration ?
Oxygen uptake and carbon dioxide removal - requires circulatory system as well
What makes up the upper airways ?
Air passages in head and neck
- opening of larynx =glottis- covered by epiglottis to prevent food entering
What makes up the respiratory tract ?
Pharynx to lungs, starting with larynx - it’s held open by cartilage
What are the 2 zones of the respiratory tract ?
Conducting zone- conducts air from larynx to lungs
Respiratory zone- contains sites of gas exchange
Describe the conducting zone
Trachea divide into 2 bronchi which divide into smaller bronchi and bronchioles
Volume is about 150ml
Air is warmed, humidified and filtered
- goblet cells secrete mucus to trap any pathogens
Trachea is surrounded by chapped cartilage to keep it open
How much mucus do you swallow each day?
1L
Describe the respiratory zone
Organised to have maximum surface area and mini is wall thickness
- about 300 million alveoli - total sa 100m squared
- alveolar wall is a single squamous epithelium layer with basement membrane membrane fused - 0.2 micrometers thick
What muscles are used in breathing ?
Diaphragm
Internal/external intercostal muscles
What are the lungs surrounded by ?
A pleura sac with a visceral pleura on the outside and a parietal pleura on the inside surface
Between these 2 pleura is intrapleural space contain 15ml intrapleural fluid
During inspiration is atmospheric or alveolar pressure greater ?
Atmospheric air is greate r
During expiration is atmospheric or alveolar air greater ?
Alveolar
What is normal atmospheric air pressure ?
760mmHg
What is intraalveolar pressure ?
0 at rest
Because it is equal to atmospheric at rest
What is intrapleural pressure ?
-4 at rest
Always less than intraalveolar
Always negative during normal breathing because opposing forces pull parietal and visceral pleura part
What is transpulmonary pressure ?
Alveolar pressure - intrapleural pressure
It is the distending pressure across the lung wall
At rest it’s about 4
What prevents 2 pleura being pulled apart ?
Surface tension intrapleural fluid
What is the functional residual capacity ?
Volume of the air in the lungs t rest when all breathing muscles are relaxed
What is a pneumothorax ?
When the lung is punctured it causes the intrapleural pressure to equilibriate with atmospheric pressure causing lungs to recoil and collapse and chest wall recoils outward
What diseases increase chances of spontaneous pneumothorax ?
Emphysema and pneumonia
- these disease damage visceral pleura allowing air from lungs to enter intrapleural space
What is boyles law ?
Gas pressure is inversely proportional to volume
What is the driving force for air into and out of the lungs ?
The difference between atmospheric pressure and alveolar pressure
As atmospheric is constant it is the alveolar pressure which determines the direction of flow
What are the 2 determinants of intraalveolar pressure ?
Quantity of air in alveoli
Volume of alveoli
Describe what happens during inspiration
Lungs expand
Alveolar volume increases so pressure decreases
Pressure gradient drives air into lungs
Describe what happens during expiration
Lungs recoil
Alveolar volume decreases and pressure increases
Pressure gradient drives air out of lungs
What respiratory muscles are involved in inspiration ?
External intercostal and diaphragm
What respiratory muscles are involved in expiration ?
Internal intercostal and abdominal muscles
What are the mechanics of inspiration ?
Diaphragm contracts and flattens moving downwards
External intercostal contract and ribs pivot up and out
Volume increases
Intrapleural pressure decreases
Transpulmonary pressure increases
Lungs expand with chest wall
Air flows in until alveolar air is equal to atmospheric
What does transpulmonary pressure provide ?
Provides the force for the expansion of the lungs
What is lung compliance ?
Ease at which lungs can inflate
What does a large lung compliance mean ?
Reduces work of breathing
What does lung compliance rely on ?
Elasticity of the lungs - elastic fibres present in connective tissue of the lungs which recoil once lungs have been stretched
Surface tension of fluid lining alveoli - measure of the amount of work needed to increase SA
During inspiration what effect does surface tension have ?
Acts to decrease lung compliance
What is surfactant ?
Secretes by type 2 alveolar cells
It decreases surface tension by interfering with hydrogen bonds and so increases compliance
Where is surfactant more concentrated and why ?
In smaller alveoli to reduce surface tension and and the internal pressure so it prevents collapse of smaller alveoli
Why is airway resistance low in healthy lungs ?
Because total sa is relatively high at each levels of branching
What does a low airway resistance mean ?
Means during normal conditions it doesn’t require a large difference between atmospheric and alveolar pressure to cause breathing
What factors determine airway resistance ?
Passive forces exerted on airways
- changes in transpulmonary pressure and tractivs forces exerted on airways
Secretion of mucus in the airways
- excessive secretion or reduced clearance causes accumulation which increases resistance
Contractile activity of bronchioles
- a decrease in bronchodilator radius increases resistance
What effect foes histamine have on the bronchioles ?
Causes bronchoconstriction
