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MP - Lecture 23

Mechanics of Breathing I

Medical Physiology – Lecture 23 Mechanics of Breathing I
Total lung capacity is made of what respiratory volumes? IRV, TV, ERV, and RV
Vital capacity is made of what lung volumes? IRV, TV, and ERV
Inspiratory capacity is made of what volumes? IRV and TV
All respiratory muscles are relaxed at: Functional Residual Capacity
Muscles of inspiration are: Diaphragm, External Intercostals, Sternocleidomastoid, and Scalene
The main muscle for normal quiet breathing is: Diaphragm
Muscles used for active breathing (inspiration) are: External Intercostals, Sternocleidomastoid, and Scalene
Muscles of expiration are: Abdominals and Internal Intercostals
At the end of expiration, lung volume equals: FRC
At the end of inspiration, lung volume equals: FRC + TV
Contracting external intercostals causes: Increase in A-P diameter of ribcage (elevate ribcage)
Contracting internal intercostals causes: Decrease in A-P diameter of ribcage (depress ribcage)
Breathing is impossible when: Both ribcage and abdomen are prevented from contracting (i.e. surrounded by rigid barrier)
At the end of inspiration, vertical and horizontal diameters are: Increased
Law of Laplace P = 2T/r (P = Pressure required to keep alveolus inflated)
Small alveoli require ___ pressure to stay inflated. high (Law of Laplace)
Collapse tendency of lung is caused by: Elastic Fibers and Surface Tension
Surfactant is secreted by: Type II Alveolar Epithelial Cells
Surfactant decreases: Surface Tension
How does surfactant prevent alveoli from collapsing? Reducing surface tension reduces required pressure to keep alveoli inflated (Laplace)
Insufficient surfactant secretion in newborns (especially premature) can cause: Infant Respiratory Distress Syndrome (IRDS)
Driving force of bulk air movement is: Pressure Difference (Between two points)
Pulmonary pressures are taken respectively to: Atmospheric Pressure
Atmospheric Pressure = ? P = 0
Subatmospheric Pressure = ? P < 0
Pleural pressure is between the: Visceral Pleura and Parietal Pleura
Pleural pressure is generally: Subatmospheric (Ppl = -5 cm H2O)
Changes in pleural pressure can be measured by: Esophageal Balloon
Driving force for airflow in and out of lungs is: Alveolar Pressure (PA)
Alveolar pressure during inspiration is: PA < 0 (Subatmospheric pressure)
Alveolar pressure during expiration is: PA > 0
Alveolar pressure with no airflow is: PA = 0 (Atmospheric pressure)
Pressure difference between inside and outside lungs is: Transpulmonary Pressure (PL)
PL = ? PL = PA – Ppl
Transpulmonary pressure determines: Degree of Inflation in the Lung
Pleural pressure equals ___ when the thorax or lung is punctured. atmospheric
During pneumothorax: Lung collapses, hemi-thorax expands, and other lung decreases because of mediastinum shift
What are the PA, Ppl, and PL after a normal expiration? PA = 0, Ppl = -5, PL = +5
What are the PA, Ppl, and PL after a normal inspiration? PA = 0, Ppl = -10, PL = +10
Created by: emyang



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