Respiratory Muscles And Breathing Cycle Flashcards
Whaat are the main muscles of inspiration?
External intercostals
Scalene
Sternocleidomastoid
Diaphragm contracts shortens and pulls flat
Bucket handle analogy
As ribs lift upward- they swing out
Increasing volune
What are the physical changes in the muscles of respiration during respiration?
Movements of the diaphragm and rib cage change thoracic volume, which allows the lungs to inflate during inspiration and deflate during expiration. At rest, during inspiration, the diaphragm contracts and and pushes the abdominal contents downward. The downward movement also pushes the rib cage outwards. With deep and heavy breathing, the accessory muscles (the external intercostals and sternocleidomastoids) also contract and pull the rib cage upward and outward. Expiration is passive during resting conditions. The diaphragm relaxes and returns to its dome shape, and the rib cage is lowered. During forced expiration, however, the internal intercostal muscles contract and pull the rib cage down and inward.Bt he abdominal muscles also contract and help pull the rib cage downward, compressing thoracic volume
Explain functioning of the pleural membrane in respiration
The visceral pleural membrane is physically attached to the lung surface so that lungs cannot deflate without pulling on the pleural membrane. Likewise, the parietal pleural membrane is attached i the wall of the thorax and diaphragm, therefore the chest wall or diaphragm cannot move out without pulling on the pleural membrane .
The chest wall pulling out and the elastic recoil of the lung pulling inwards means that the pleural space naturally has a negative pressure associated with it.
What is the correlation of pressure and force?
Pressure = force per unit area=F/A
Therefore, increasing surface area (volume)= drop in pressure
What is the formula of the combined gas laws?
P1V1/T1= P2V2/T2
increase temperature= increase in volume
So as air flows into the lungs and warms up it will increase in volume (marginal effect)
More importantly + pressure volume
Increasing volume in closed system will cause a pressure drop
What was Robert Boyles low?
P1V1= P2V2
Pressure falls as volume increases
Use syring as example
What is the significance of pressure gradients in respiration?
Pressures change during breathing. Several important pressures are involved in breathing: airway pressure (Paw), alveolar pressure (PA), pleural pressure(Ppl), trans pulmonary pressure (PL), and trans airway pressure (Pta). Both trans pulmonary and trans airway pressure can be defined as pressure inside minus the pressure outside. In both cases, the pressure outside is pleural pressure
What creates a negative pleural pressure?
A negative pleural pressure results from the elastic recoil of the lungs and chest wall pulling in opposite directions. The stretched lung (at the end of a normal inspiration) tends to recoil inwardly, and the chest wall tends to recoil outwardly, but in equal and opposite directions . Consequently, pleural pressure (Ppl) becomes negative (I.e. less than atmospheric pressure). Rupture or puncture of the lung or chest wall results in a pneumothorax, during which the trans pulmonary pressure becomes zero and elastic recoil causes the lung to collapse.
The mediastinal membrane prevents the other lung from collapsing. Pa, alveolar pressure
What are the pressure changes during breathing?
- Inspiratory muscles contract
- Thoracic cavity expands in volume
- Pleural pressure falls ((from -5 to -8)
- Trans pulmonary pressure gradient increases PTP= PA-PIP
- increase in PTP causes alveolar expansion whilst decrease in PTP causesalveolar recoil
- Alveoli expand in volume
- Alveolar pressure falls (from 0 to -1)
- Air flow down the gradient from PATM to PA
Summarize the breathing cycle
Inspiration at 2 sec is slightly quicker than expiration (3 sec)
Note- only small pressure changes in the alveolus are required to drive sufficient flow during normal tidal breathing
Why is expiration slower than inspiration and why is a grater DPA required to drive expiration than inspiration
Increased airway resistance during expiration (radial traction falling and for forced expiration dynamic airway compression) therefore pressure gradients are larger and dissipate more slowly
How does airflow resistance impact expiratory time?
Airflow resistance affects expiratory time. The inspiratory time (Ti) is 2 seconds and is less than the expiratory time (Te) of 3 seconds. This difference is a result of, in par, a higher airflow resistance during expiration, as is reflected by a higher alveolar pressure (PA) change during expiration (12 cm H2O) than during inspiration (0.8 cm HSO). An increase in airway resistance will decrease the Ti/Te ratio. Only a small pressure change between the mouth and alveoli is required for a normal tidal volume
How can lung compliance be measured?
Lung compliance is measured by pressure-volume curve. The subject first inspires maximally to total lung capacity (TLC) and then expires slowly, while airflow is periodically stopped to simultaneously measure pleural pressure and lung volume. Lung compliance (CL) is measured in L/cm H2O . Note that pleural pressure is determined by measuring esophageal pressure. FRC, functional residual capacity; P, pressure, RV,
How can lung compliance be measured?
Lung compliance is measured by pressure-volume curve. The subject first inspires maximally to total lung capacity (TLC) and then expires slowly, while airflow is periodically stopped to simultaneously measure pleural pressure and lung volume. Lung compliance (CL) is measured in L/cm H2O . Note that pleural pressure is determined by measuring esophageal pressure. FRC, functional residual capacity; P, pressure, RV, residual volume; Vt, tidal volume
