Mechanics Flashcards
Result of Muscle Contraction:
descend downward increasing the vertical dimension of the throacic cavity
Diaphragm
Result of Muscle Contraction:
Elevate the lower ribs upward and outward, enlarging the thorax in both the front-to-back and side-to-side dimensions
External Intercostals
Result of Muscle Contraction:
Raise the sternum and elevate the first two ribs, enlarging the upper portion of the thoracic cavity
scalene and sternocleidomastoid
Result of Muscle Contraction:
Maintains patency of the conducting upper airways to reduce airflow resistance
Muscles of the upper respiratory tract
The Inspiratory Muscles include:
diaphragm, external intercostals, scalene and sternocleidomastoid and muscles of the upper respiratory tract
Result of Muscle COntraction:
Increase the intra-abdominal pressure, which exerts an upward force on the diaphragm to decrease the vertical dimension of the thoracic cavity
abdominal muscles
Result of Muscle Contraction:
flatten the thorax by pulling the ribs downward and inward, decreasing the front-to-back and side-to-side dimensions of the thoracic cavity
internal intercostals
The expiratory muscles include:
abdominal muscles and internal intercostals
Timing of Stimulation to Contract:
Only during active (forced) expiration
abdominal muscles and internal intercostals
Timing of Stimulation to Contract:
Only during forced inspiration; accessory inspiratory muscles
Scalene and sternocleidomastoid and muscles of the upper respiratory tract
Timing of Stimulation to Contract:
During active inspiration; the primary muscle of inspiration
Diaphragm
Timing of Stimulation to Contract:
During active inspiration; play a secondary role to the primary action of the diaphragm
external intercostals
Expiration (at rest) to functional residual capacity is ___ due to the elastic recoil of the lungs
passive
Expiration is ___ as needed for exercise or beyond FRC
active
In a person breathing rhythmically while sleeping, the expiration of tidal volume would be due to
a) contraction of the abdominal muscles
b) elastic recoil of the lung tissue
c) elastic recoil of the chest wall
d) contraction of the diaphragm
b
In a person breathing rhythmically while sleeping, the inspiration of tidal volume would be due to
a) contraction of the abdominal muscles
b) elastic recoil of the lung tissue
c) elastic recoil of the chest wall
d) contraction of the diaphragm
d
During forced inspiration, which muscle is not contracting
a) diaphragm
b) external intercostal
c) internal intercostal
d) scalene
c
Intrapleural, pleural, or intrathoracic pressure
pressure within the pleural cavity exerted outside the lungs within the thoracic cavity; usually less than atmospheric pressure
intrapulmonary or alveolar pressure
the pressure within alveoli. bc alveoli communicate with the atmosphere thru conducting airways, air quickly flows down its pressure gradient any time intrapulmonary pressure differs from atmospheric pressure
transpulmonary pressure
difference in pressure between the inside and outside of the alveoli; it is equal to intrapulmonary pressure minus the intrapleural pressure
Pressures During breathing Cycle:
Start inspiration
Diaphragm contracts
chest volume increases
pleural pressure decreases
alveolar pressure decreases
air flows into lungs
volume of air in lungs increases
pressure equilibrate
Pressures During breathing Cycle:
Passive expiration
diaphragm relaxes
chest volume decreases
intrapleural pressure increases
alveolar pressure increases
air flows out of lungs
volume of air in lungs decrease
pressures equilibrate
At the start of inspiration, there is a fall in
a) atmospheric pressure
b) intra-alveolar pressure
c) intra-pleural pressure
d) intra-alveolar and intra-pleural pressure
d
towards the end of inspiration, there is an increase in
a) atmospheric pressure
b) intra-alveolar pressure
c) intra-pleural pressure
d) intra-alveolar and intra-pleural pressure
b
At the end of inspiration, which two pressure are equal?
a) atmospheric & alveolar
b) atmospheric & pleural
c) alveolar & pleural
d) atmospheric, alveolar & pleural
a
Which of the following events occurs first to start the normal sequence of inspiration?
a) intrapulmonary pressure decreases
b) intrapleural pressure becomes more negative
c) air flows into the lungs, causing an increase in intrapulmonary pressure
d) diaphragm contracts
d
Elastic Properties of the Lung:
Elastin primarily contributes to the elasticity
Collagen limits ___
over-expansion
Lung Compliance:
Pulmonary Fibrosis
involves an increase in fibrous material within the lung interstitium. causes the lungs to stiffen which decreases lung compliance; when the elastic recoil fo the lung is increased, normal changes in transpulmonary pressure produce smaller than normal changes in lung volume; lung compliance is also decreased with alveolar edema or if pulmonary venous pressure is increased; these conditions inhibition proper inflation of alveoli
Lung compliance:
Emphysema
degradation of the elastin and collagen framework of the lung parenchyma; results from excessive release of destructive enzymes such as trypsin from alveolar macrophages in response to chronic exposure to cigarette smoke or other inhaled chemical irritants; emphysema markedly decreases the elastic recoil of the lung, thereby increasing the compliance of the lung; reduction of radial traction that keeps small airways stretched open –> leads to airway collapse and increase in airway resistance during expiration
Elastic recoil v radial traction
elastic recoil and radial traction are both caused by the effects of elastin on lung tissue; the elastin that surrounded a single airways produces radial traction that keeps the airway open; overall, the elastin in the lung works to produce inward recoil
Surface tension:
the air-liquid interface exists in the alveoli
the interface generates surface tension that behaves like a thin bubble that is prone towards collapse and resists the expansion of the alveoli during inspiration
- two alveoli of unequal sizes but having the same surface tension are joined together by same terminal airway, the alveolus with a small radius will have a higher pressure and will empty its air into larger alveolus
Surfactant is a…
lipid protein complex that is produced by type II alveolar cells; it contains hydrophobic and hydrophilic regions that allow it to incorporate into the air-liquid interface
Surfactant increases the ___ of the lung by reducing ___ that would draw fluid to the alveolar surface
compliance; surface tension
The second property of surfactant is that as the surface area of a surfactant film is increased…
the surface tension increases
Surfactant Medical Consideration:
Type II alveolar cells produce surfactant at ___ gestation
30 weeks; infants > 10 weeks premature may develop respiratory distress syndrome
