Respiratory system 2 + 3 Flashcards
Air flow and pressure changes
respiratory pressure cycle
End of Expiration
Alveolar/ intra pulmonary pressure = atmospheric pressure
No air movement
Inspiration
Increased thoracic volume >
Increased alveolar volume
Decreased alveolar pressure
Atmospheric pressure > alveolar pressure
Air moves into lungs
End of Inspiration
Alveolar pressure = atmospheric pressure
No air movement
Expiration
Decreased thoracic volume
Decreased alveolar volume
Increased alveolar / intrapulmonary pressure
Alveolar pressure > atmospheric pressure
Air moves out of lungs
What is pleural pressure?
the pressure in the pleural cavity
Normally lower than alveolar pressure.
Suction effect - fluid removal by the lymphatic system
Negative pressure difference (lower pleural pressure than alveolar pressure) - role?
keeps the alveoli expanded
-ive pressure significance
Pulls the pleura away from the outside of the alveoli
Pressure on the alveoli is lower
Expansion is opposed by the tendency of the lungs to _____
recoil
Pneumothorax
Pleura pierced
Pneumothorax : Pleura pierced
Air introduced
Pleural pressure is not low enough to overcome lung recoil
Alveoli collapse
volume larger
more air sucked in
Inspiration
Active process(needs energy)
Signals from the respiratory centre in the medulla oblongata (brain stem) >
Contraction of the diaphragm and intercostal muscles leading to the diaphragm moving downward >
Transverse expansion of thoracic cavity
+
Vertical expansion of thoracic cavity
>
Lung volume increases and the intra-alveolar pressure decreases >
Air is sucked in (inhalation)
ExhalationPassive process - what kind of energy needed?
elastic potential energy
The process of exhalation:
A passive event due to elastic recoil of the lungs
Relaxation of diaphragm and external intercostal muscles
During forced expiration, ONLY there is contraction of abdominal, internal intercostal (accessory muscles)
Characteristics of
No inherent rhythm
Generate tension due to rhythmic pattern of neuron-induced action potentials activating them
Muscles attempt to overcome the resistance to airflow within the airways
When at rest, the thorax assumes the FRC (Functional Residual capacity) position
Respiratory Function: measurement
Spirometry is the process of measuring volumes of air that move into and out of the respiratory system
measure respiratory volumes: peak flow (info on health of lungs)
Volumes and Capacities
Respiratory volumes:
measures of the amount of air movement during different portions of ventilation,
Respiratory capacities
Sums of two or more respiratory volumes
How many litres does the total of volume of air contain in the respiratory system?
4-6L
Tidal Volume (VT)
The volume of gas expired/inspired in one breathing cycle
Also known as ‘resting’ or ‘quiet’ breathing
Inspiratory reserve volume
Inspiratory reserve volume is the amount of air that can be inspired forcefully beyond the resting tidal volume
Expiratory reserve volume
Expiratory reserve volume is the amount of air that can be expired forcefully beyond the resting tidal volume
Residual volume
Residual volume is the volume of air still remaining in the respiratory passages and lungs after maximum expiration
Without a residual volume, the lungs would completely collapse and the pressure required to generate inflation would be high
Total lung capacity (TLC)
The volume of gas in the lungs and airways at a position of full inspiration – therefore we are measuring how much air the lungs can actually hold
Lung expansion is limited at a point which defines TLC
Breathing out maximally does not mean you breathe ____ air out of lungs
ALL
Vital Capacity (VC)
The total volume of gas that can be expired from the lungs from a position of full inspiration/ the total volume of gas that can be inspired from a position of residual volume
This is similar to an FVC manoeuver except it is not forced
Inspiratory capacity
The tidal volume plus the inspiratory reserve volume
The amount of air a person can inspire maximally after a normal expiration
Functional Residual Capacity fluctuates between
lung recoil and chest wall
Limits of Spirometry
Cannot measure TLC, FRC, RV
Dynamic Lung Volumes
Rate at which air moved