II: Respiratory System Unit Flashcards
Pleura formed by
Parietal and visceral pleura
Parietal pleura composition
Fibrous membrane
With what is the parietal membrane in contact with
Thoracic cage
With what is the visceral layer in contact with
Lungs
Barometric pressure definition
Pressure of the atmosphere (the air)
At the end of respiration both barometric and alveolar pressures =
0
What causes a difference of -1 between alveolar and barometric pressure
The retraction of the diaphragm
What causes air to move to the interior of lungs
The difference of -1 between alveolar and barometric pressure
At the end of inspiration, barometric and alveolar P are
Equal
What causes air to move out of the lung
During expiration, the diaphragm relaxes to Palveolar»_space; Pbarometric
Process of air coming in and out (TODO)
Before inhalation (P barometric and P alveolar = 0)
During inhalation the diaphragm contracts so Palveolar decreases. There is a difference of -1 between alveolar and barometric pressure
At the end of inhalation Palveolar = Pbarometric because P alveolar is 0 again
Diaphragm stops retracting, thoracic cage decreases in volume, Palveolar»Pbarometric so air comes out of lungs
Why does inspiration occur
Due to the differences in barometric and alveolar pressure
What facilitates inspiration
Respiration muscles
What is hysteresis
Differences in volumes during inspiration and expiration, at the same pressure
What is closing capacity, CC
Volume at which the smallest airways collapse
Does the lung ever run out of air
No, starting point is never 0 due to the closing capacity
The intrapleural pressure is always
NEGATIVE
What keeps the lungs in the rib cage
The negative intrapleural pressure
Ppleural at upper poles =
-10cmH2O
Ppleural at lower poles
-2cmH2O
Greater distensibility in
Upper alveoli because they are larger
Greater expanding capacity in
Lower alveoli so they participate more in ventilation
Lung compliance definition
Change in volume in lungs at a given pressure
Average lung compliance in lung
200mL/cmH2O
The greatest distensibility found at
Intermediate zones
Pulmonary emphysema cause
Intralveolar septa are ruptures
Consequence of pulmonary emphysema
More air enters the lungs at low pressures
No effective gas exchange due to low pressures
Decrease in O2 –> dyspnea
More distensibility (due to decreased resistance) –> more compliance
What increases distensibility in pulmonary emphysema
The lack of resistance
Pulmonary fibrosis cause
Septa are thickenes
Consequences of pulmonary fibrosis
Greater resistance to be overcome
Less distensibility = less compliance
What is surface tension
The energy exerted on a surface to maintain its SA/unit area
What cancels surface tension in alveolis
Surfactant produced by type II pneumocytes
How do pneumocytes work
They exert forces in all directions to forces cancel
Blockage of airways leading to alveoli will cause
Alveolar collapse
LaPlace’s law:
Gradient pressure = 2y/r
y = surface tension r = alveolar radius
Pressure required to keep alveoli expanded is greater in small or large alveoli
Small
Why is there exchange between small and large alveolus
Because ∆P is greater in small alveolus
Types of exchange between small and large alveolus
Equal exchange: 2 alveolus = in size so air flowing in and out is equal
Non-equitational exchange: more air exiting airways + entering in small alveolus
Compositino of surfactant
(90% lipids and 10% H2O)
Functions of surfactant
Decrease ST
Increase stability
Prevent pulmonary edema
Production of surfactant according to the size of alveolus
Large alveolus produce SMALL surfactant –> decrease in size
Small alveolus produce LARGE surfactant –> maintain size
Respiratory distress syndrome in newborns occurs due to
Lack of surfactant –> stiffness and little distensibility in lungs
