Term
| Describe the respiration we do each day in numbers |
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Definition
| Each day, we each take around 20,000 breaths, inhaling and exhaling around 10,000 litres of air. |
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Term
| How long can you survive without air? |
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Definition
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Term
| What is the major function of pulmonary ventilation? |
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Definition
to exchange O2 and CO2 between the lung air spaces and the blood.
- O2 moves from the lung air space into the blood, into the internal environment.
- CO2 moves from the lung air space out of the blood, into the external environment. |
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Term
| What are the secondary functions of the respiratory system? (6) |
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Definition
1. Acid – Base balance (via regulation of PaCO2)
2. Vocalisation (communication)
3. Defence against pathogens
4. An avenue for water and heat losses
5. Enhancing venous return (via the respiratory pump)
6. Activating some plasma proteins as the pass through the pulmonary circulation |
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Term
| Define internal respiration |
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Definition
| also known as cellular respiration; refers to the use of O2 to generate ATP within the mitochondria via oxidative phosphorylation |
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Term
| Define external respiration |
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Definition
| refers to the exchange of O2 and CO2 between the atmosphere and body tissues (this involves both the respiratory and circulatory systems) |
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Term
| Give the 3 integrated steps of external respiration |
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Definition
1. Pulmonary ventilation: physically moves air into and out of the lungs.
2. Gas diffusion across the respiratory membrane: between the alveolar air spaces and alveolar capillaries, and across capillary walls between blood and other tissues.
3. Transport of O2 and CO2 between alveolar capillaries and capillary beds in other tissues. |
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Term
| What makes up the upper airways? |
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Definition
| air passages in the head and neck (nasal and oral cavities and the pharynx) |
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Term
| What makes up the respiratory tract? |
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Definition
| All airways leading from the pharynx to the lung (including those within the lungs themselves), starting with the larynx. It can be functionally divided into 2 components: the conducting zone and the respiratory zone |
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Term
| What makes up the conducting zone? |
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Definition
| The conducting airways include the passage of air in everything from the larynx to the terminal bronchioles. |
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Term
| What does the trachea divide into? |
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Definition
2 primary bronchi
which then subdivide into successively smaller bronchi and bronchioles (23-30 orders of branching occur) |
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Term
| What is the primary function of the conducting zone? |
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Definition
| to provide a route for air to enter and leave the respiratory zone (where gas exchange occurs) |
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Term
| What is the air in the conducting zone called? |
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Definition
dead space: the volume of inhaled air that does not take part in gas exchange because either it remains in the conducting airways, or reaches alveoli that are not or poorly perfused
150ml |
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Term
| What happens to air in the conducting zone? |
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Definition
- warmed and humidified
- filtered (goblet cells secrete mucus, ciliated cells propel the mucus towards the glottis) |
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Term
| What allows changes in bronchiolar diameter? |
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Definition
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Term
| Why is PO2 in the air different to PO2 in the alveoli? |
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Definition
because air inhaled into the alveoli is partly air from the dead space, which contains less o2 and more co2 (diluting effect of dead space air)
also air is humidified so water vapour pressure is added to dry gas pressure. total pressure doesn't change so dry pressures must decrease |
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Term
| What are the benefits of the conducting zone? |
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Definition
•CO2 is retained, making a bicarbonate-buffered blood and interstitium possible.
•Inspired air is brought to body temperature, increasing the affinity of haemoglobin for O2, improving O2 uptake.
•Particulate matter is trapped in the mucus that lines the conducting airways, allowing its removal by mucociliary transport. Defence!
•Inspired air is humidified, improving the quality of airway mucus. |
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Term
| What is the function of the respiratory zone? |
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Definition
| The function of alveolar air space is gas exchange! There are around 300million alveolar sacs with a combined maximal surface area of around 100m2. |
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Term
| Define alveolar dead space |
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Definition
| : the sum of the volumes of those alveoli which have little or no blood flowing through their adjacent pulmonary capillaries, i.e., alveoli that are ventilated but not perfused, and where, as a result, no gas exchange can occur. |
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Term
| What factors increase the rate at which substances diffuse across a membrane? |
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Definition
membrane surface area increase
membrane thickness decrease |
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Term
| How many alveolar are there and what is their total SA? |
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Definition
| There are ~ 300 million alveoli, with a total SA of ~ 100m2 |
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Term
| What does the alveolar wall consist of? |
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Definition
| a single layer of squamous epithelial cells, whose basement membrane is fused with that of the capillary endothelium. The total thickness of this barrier is only about 0.2 μm |
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Term
| What muscles are responsible for breathing? |
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Definition
| the diaphragm and the internal and external intercostals |
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Term
| Describe the thoracic cavity |
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Definition
| The lower end of the thoracic cavity is sealed off by the diaphragm, and the upper end by structures of the neck, so the compartment enclosing the lungs is airtight |
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Term
| What surrounds each lung? |
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Definition
a membrane called the pleura
visceral - lines the exterior surface
parietal - lines the interior |
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Term
| Whats lies between the pleura? |
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Definition
| lies the intrapleural space, containing around 15 mL of intrapleural fluid (an aqueous solution) |
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Term
| What is the function of the pleura? |
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Definition
| The pleurae aid lung function: lubricated pleural fluid reduces mechanical resistance during ventilation, providing surface tension to attach the lungs to the chest walls. Pressure changes during ventilatory behaviour also occur. |
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Term
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Definition
| air flow into or out of the lungs is an example of bulk flow, driven by a pressure gradient between the air in the alveoli and the atmosphere |
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Term
| What must happen in order for inspiration to occur? |
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Definition
| atmospheric pressure must exceed alveolar pressure (vice versa for expiration) |
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Term
| What are the 4 pressures associated with ventilation? |
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Definition
Atmospheric pressure (Patm): taken to be 760 mmHg
Intra-alveolar pressure (Palv): 0 mmHg ‘at rest’
Intrapleural pressure (Pip): -4 mmHg ‘at rest’. This is the pressure within the pleural sac
Transpulmonary pressure ( = Palv – Pip). This is the distending pressure across the lung wall: at rest, this is around 4 mmHg, which is just enough to balance the elastic recoil forces within the lung and represents a state of equilibrium |
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Term
| Which pressure is always less than another pressure during normal breathing? |
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Definition
Pip is always less then Palv and is always negative during normal breathing
Pip is always negative during normal breathing |
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Term
| What is meant by the fact that the chest and lungs are both elastic structures? |
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Definition
| they tend to recoil towards their natural positions when stretched or compressed |
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Term
| Describe the lungs and chest wall at rest |
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Definition
chest: compressed and recoils outwards
lungs: stretched and recoils inwards
forces tend to move the lungs and chest wall apart |
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Term
| Why don't the lungs and chest wall separate? |
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Definition
| the surface tension of the intrapleural fluid prevents the visceral and parietal pleura from pulling apart, so a negative intrapleural pressure develops |
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Term
| What state are breathing muscles in at rest? |
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Definition
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Term
| What is the functional residual capacity (FRC)? |
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Definition
| the volume of air within the lungs at rest |
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Term
| What happens if the pleural sac is punctured? |
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Definition
- Pip equilibrated with Patm at 0mmHg
- the lungs recoil and collapse (chest wall recoils outwards)
pneumothorax |
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Term
| If one lung is punctured, what happens to the other? |
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Definition
| each lung is enclosed in its own pleural space, so the unaffected lung should continue to function |
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Term
| When might a spontaneous pneumothorax occur? |
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Definition
| if disease (e.g. pneumonia, emphysema) damages the visceral pleura so that air from the lung enters the intrapleural space |
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Term
| What does Boyle's Law state? |
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Definition
gas pressure is inversely proportional to volume:
P α 1/V |
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Term
| How does Boyle's Law relate to the lungs? |
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Definition
| the pressure in the lungs changes when their volume changes |
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Term
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Definition
pressure gradient divided by resistance:
Flow = (Patm – Palv) / R |
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Term
| What is the driving force for air movements in and out of the lungs? |
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Definition
| the driving force for air movements in and out of the lungs is the difference between Patm and Palv and since Patm is constant, changes in Palv determine the direction and rate of air movement |
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Term
| What two factors determines intra-alveolar pressure? |
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Definition
- Quantity (moles) of air in the alveoli
- The volume of the alveoli |
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Term
| Describe the events of inspiration |
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Definition
lungs expand
alveolar volume increases
Palv decreases
pressure gradient drives air into the lungs |
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Term
| Describe the events of expiration |
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Definition
lungs recoil
alveolar volume decreases
Palv increases
pressure gradient drives air out of the lungs |
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Term
| What are the major respiratory muscles for inspiration? |
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Definition
external intercostal muscles
diaphragm |
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Term
| What are the major expiratory muscles for inspiration? |
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Definition
internal intercostal muscles
abdominal muscles |
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Term
| How is inspiration caused? |
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Definition
1. diaphragm contracts, flattening and displacing downwards
2. external intercostal muscles contract, causing he ribs to pivot upwards and outwards
3. thoracic cavity volume increases
4. Pip decreases (becomes more negative)
5. transpulmonary pressure increases
6. lungs expand with the chest wall
7. Palv decreases to below Patm
8. Air flows into the lungs until Palv equals Patm
9. stronger contractions of the inspiratory muscles result in a greater lung expansion and a deeper inspiration |
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Term
| Describe expiration in quiet breathing |
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Definition
passive
relaxing the inspiratory muscles allows the lungs and chest wall to recoil to their resting positions |
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Term
| What happens are lung volume decreases? |
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Definition
| Palv exceeds Patm and air flows out until lung volume equals FRC (equilibrium) |
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Term
| What does more forceful expiration require? |
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Definition
contraction of the expiratory muscles: internal intercostals and some abdominal muscles
this causes a greater and more rapid decrease in thoracic volume, further increasing Palv and causing a greater and more rapid expiration |
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Term
| What does the pressure gradient for ventilation (Patm - Palv) provide the force for? |
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Definition
| moving air into and out the lungs |
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Term
| What does the transpulmonary (Palv - Pip) provide the force for? |
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Definition
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Term
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Definition
| A measure of the ease with which the lungs can be inflated. The change in lung volume (ΔV) in response to a given change in transpulmonary pressure (ΔPalv – Pip) |
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Term
| Is lung compliance good or bad? |
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Definition
| In general, a large lung compliance is advantageous, as it reduces the work of breathing |
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Term
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Definition
| the resistance to air flow imposed by all the airways in the respiratory tract |
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Term
| What is resistance most sensitive to? |
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Definition
airway radius
as radius decreases, airway resistance increases. |
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Term
| What level of resistance is desirable? |
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Definition
| In general, a low level of airway resistance is desirable; again, this reduces the work of breathing |
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Term
| What does lung compliance depend on? |
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Definition
The structural elasticity of the lungs
The surface tension of the fluid lining the alveoli |
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Term
| How does structural elasticity of the lungs affect lung compliance? |
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Definition
Due to the presence of elastic fibres in the connective tissue of the lung: forces in the elastic fibres oppose lung expansion
Lung stretches = fibres recoil |
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Term
| How does surface tension of the fluid lining the alveoli of the lungs affect lung compliance? |
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Definition
| The surface tension of a liquid is a measure of the work needed to increase its surface area by a given amount: the greater the surface tension, the more work needed. |
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Term
| What causes surface tension in the lungs? |
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Definition
In the lungs, surface tension occurs as a result of the air-liquid interface formed by the thin layer of liquid lining the internal surface of the alveoli.
As the lung expands, so does the fluid layer in the alveoli. Therefore, during inspiration, the surface tension acts to decrease lung compliance |
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Term
| What does type II alveolar cells secrete? |
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Definition
| a detergent-like substance called pulmonary surfactant into the fluid lining the alveoli |
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Term
| What is the function of pulmonary surfactant? |
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Definition
| This phospholipid decreases surface tension by interfering with the hydrogen bonding between water molecules, thereby increasing lung compliance and decreasing the work of breathing |
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Term
| What would happen in the absence of surfactant? |
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Definition
| the smaller alveolus would indeed collapse, increasing the internal air pressure and moving air into the larger alveolus down the pressure gradient |
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Term
| Describe infant respiratory distress syndrome |
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Definition
| Surfactant production begins relative late during fetal development, and premature babies are often deficient, leading to potentially fatal breathing problems |
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Term
| Why is airway resistance low in healthy lungs? |
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Definition
total cross sectional area of the airways at each order of branching is relatively high (and actually increases at the level of the bronchioles due to the extensive branching)
greater surface area = greater units in parallel therefore lower resistance |
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Term
| What does lower resistance mean for the respiratory pressures gradient? |
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Definition
Palv does not need to differ from Patm to generate pressure gradient necessary for normal air flow
Darcy's Law = pressure gradient/resistance |
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Term
| Give the Palv and Patm pressure gradient in quiet breathing |
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Definition
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Term
| What happens if airway resistance increases? |
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Definition
| a larger pressure gradient is required to produce a given rate of air flow |
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Term
| What factors determine airway resistance? (3) |
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Definition
1. Passive forces exerted on the airways
2. Secretion of mucus into the airways
3. Contractile activity of bronchiolar smooth muscle |
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Term
| What passive forces exert on the airways? |
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Definition
| These include changes in transpulmonary pressure during the respiratory cycle, and tractive forces exerted on the airways by the tissues surrounding them |
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Term
| Explain how passive forces exerted on the airways determine resistance |
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Definition
During inspiration, transpulmonary pressure increases, which pulls outwards on the airways causing them to distend
As surrounding tissue moves away from the airways during inspiration tractive forces exerted by the tissues increase, pulling the airways open and reducing resistance |
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Term
| Explain how secretion of mucus into the airways determine resistance |
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Definition
| Secretion of mucus into the airways by goblet cells is part of the air filtering and airway defence mechanisms, however excessive secretion or reduced clearance (often due to ciliary paralysis) may lead to accumulation of mucus, which increases airway resistance |
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Term
| Explain how contractile activity of bronchiolar smooth muscles determine resistance |
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Definition
| When this circular smooth muscle contracts, it decreases bronchiolar radius and increases resistance to air flow. The state of contraction is under both extrinsic (neural and hormonal) and intrinsic (local chemical mediator) control |
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Term
| Explain neural control of bronchiolar smooth muscles |
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Definition
| Sympathetic stimulation (and circulating adrenaline) cause bronchodilation; parasympathetic stimulation causes bronchoconstriction |
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Term
| Explain hormonal control of bronchiolar smooth muscles |
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Definition
| Histamine (released locally during allergic reactions) causes bronchoconstriction |
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Term
| Explain intrinsic control of bronchiolar smooth muscles |
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Definition
| An increase in local CO2 levels causes bronchodilation (important in ventilation : perfusion matching) |
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Term
| Name 2 pathological conditions associated with increased airway resistance |
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Definition
| asthma and chronic obstructive pulmonary diseases (COPDs) |
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