What is the function of the conducting zone of the lungs?
Way of transporting gases into the respiratory zone
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What makes up the conducting zone?
Nose, mouth, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles
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What number branch is the bronchi?
11
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What branch is the 0?
Trachea
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What supports the bronchi?
Cartilage
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What supports the bronchioles?
No cartilage Rely on tissue around them and their elastic nature to keep them open Much more subject to contraction
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Why is it more efficient if we breathe through our nose?
Small hairs help filter and trap particles As the air is moving through it creates a turbulent type condition - smaller particles are more likely to drop our or get trapped because of this
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Why is it beneficial for air to warm to our body temperature?
Warming gas helps prevent the formation of bubbles
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What can carry more gas warm or cold air?
Cold
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What stops the lower airways from drying out?
As air passes through it becomes humidified and equilibrated with water vapour
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What controls the contraction of bronchi?
Smooth muscle underneath the cartilage lining the outside of bronchi under the control of para/sympathetic innervation
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Epithelia mucous gland
Secretes mucus onto surface of bronchi to help trap particles
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Function of elastic tissue in the airways
Recoil and helps to support
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Function of ciliated epithelium in the lumen of the airways?
Helps direct mucus out of the lungs towards the throat to move small particles out of the lungs
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Goblet cells
Produce mucus
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Function of sensory nerve endings between epithelial cells in bronchi and bronchioles
Help detect noxious chemicals in the airway e.g. smoke
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Diameter of bronchioles
Less than 1mm
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What keeps bronchioles open?
Tethering of tissue around them - elastic tissue connection helps keep them open
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What breaks down in COPD?
The elastic tissue surrounding the bronchioles subjecting them to collapse
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Why do the bronchioles have proportionally more smooth muscle cells compared to the bronchi?
Controlling the airway diameter is more important
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How many alveoli?
300 million per lung
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Surface area of alveoli?
100 m2
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How many biological membrane does oxygen have to diffuse across?
5
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Inspiration pressure gradients
Atmospheric pressre is greater than the pressure inside the alveoli so gas moves down the pressure gradient and into the lungs
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Expiration pressure gradients
Pressure in alveoli is greater than atmospheric pressure so gas moves down the pressure gradient and out of the lungs
Attach to top of rib cage - contraction helps move the rib cage up and forward
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Function of sternocleidomastoids in forced inspiration?
Attach to the sternum - and helps to lift the sternum up and forwards
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What is the function of neck and back muscles during forced inspiration?
Pull pelvic girdle up
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Function of elastic tissue in quiet expiration?
Recoil of the elastic tissue returns the lungs to their original size
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Function of abdominal muscles in forced expiration?
Pull diaphragm up
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Pleura
Double-layered membrane surrounding each lung
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Parietal pleura
Outer layer of pleura lying closer to the ribs and chest wall
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Visceral pleura
Inner layer of pleura lying closer to the lung tissue
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Pleural cavity
Between parietal and visceral pleura
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What is the pleural cavity filled with?
Serous fluid
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Function of pleural cavity?
Allows lung and chest wall to move over each and prevent them from sticking together Enables free expansion and collapse of lungs Helps set resting lung volume
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Pneumothorax
Collapsed lung - air in the pleural cavity Intrapleural space is at atmopsheric pressure and so force keeping lungs inflated is lost Elastic nature will take over and lungs will collapse
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Is the pressure in the intrapleural space greater or less than atmospheric pressure?
Less
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Compliance
Measure of how distensible the lungs are - how elastic they are
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Concentration \=
Change in volume/ change in pressure
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As you inspire, what happens to intrapleural pressure?
Becomes more negative
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Low compliance
Large pressure chaneg and small volume change - more work needed to expand the lungs
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Pulmonary fibrosis
Build up of structural tissue in the lungs - more rigid so harder to expand Lower compliance of the lungs
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High compliance
Small pressure change induces a large volume change
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What can high compliance lead to?
Problems when expiring Emphysema/COPD Lost some elastic properties as a result of breakdown of tissue Airways can collapse Harder to breathe out
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What are the 2 components of elastic recoil in the lungs?
Anatomical and surface tension
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Surface tension in the lungs
Air/water interface - water molecules tend to be pulled into the body of water
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Laplace's equation
P\=2T/r
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What produces surfactant?
Type 2 pneumocytes
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Surfactant
Chemical produced in the lungs to maintain the surface tension of the alveoli and keep them from collapsing
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What is surfactant composed of?
90% phospholipids and 10% proteins
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How does surfactant prevent alveolar collapse?
Decreasing surface tension Inncreasing compliance
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How does surfacant affect rate of inflation?
SLows
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Production of surfactant decreases and causes what?
Pneumonia
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What happens to surfactant in pneumonia?
Production decreases
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What does surfactant prevent?
Oedema Reduces fluid entering alveoli
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How are surface tensions balanced out between large and small alveoli?
Small alveoli have a higher density of surfactant compared to large
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Dead space
Volume of lungs not involved in gas exchange
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Anatomical dead space
Conducting zone volume - first 16 generations of airways
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How much inspired air volume is dead space?
30%
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At rest how many ml of air is in anatomical dead space?
150ml
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Tidal volume
Amount of air we breathe in and out in one breath
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Average tidal volume
500ml
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Physiological dead space
Volume of lungs not participating in gas exchange Conducting zone + non-functional areas of respiratory zone Normally physiological dead space and anatomical dead space are almost identical
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2 types of dead space in lungs
Anatomical and physiological
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Vital capacity
Maximum amount of air we can breathe in and out
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Residual volume
Amount of air remaining in the lungs after a forced exhalation
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Total lung capacity
Residual volume + vital capacity
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Forced expiratory volume
How much air can be forced out of the lungs in 1 second
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Expiratory reserve volume
Amount of air that can be forcefully exhaled after a normal tidal volume exhalation
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Vital capacity \=
TV + IRV + ERV
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Inspiratory reserve volume
Amount of air that can be forcefully inhaled after a normal tidal volume inhalation
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Functional residual capacity
Volume of air remaining in the lungs after a normal tidal volume expiration
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FRC \=
ERV + RV
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Inspiratory capacity
Maximum amount of air that can be inhaled after a normal tidal expiration
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What happens to tidal volume during exercise?
Increases
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What happens to IRV and ERV if tidal volume increases?
IRV and ERV must decrease
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How to measure residual volume?
Helium dilution Measure the helium concentration before and after
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Relationship between flow of air and pressure gradient?
Flow of air is proportional to the pressure gradient
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Relationship between flow of air and resistance?
Flow of air is inversely proportional to resistance
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Poiseuille's Law
Airway resistance is proportional to gas viscosity and the length of the tube but is inversely proportional to the 4th power of the radius