ch 22 part 2
what do external intercostals do during contraction?
-elevate the ribs -Increases thoracic volume in addition to that of the diaphragm contraction -Responsible for ~25% of the air entering the lungs during quiet breathing
during Pneumothorax Intrapleural pressure goes from -4 to 0 thus doing what?
-eliminating the transpulmonary pressure that keeps a lung open -Inward forces dominate and lung collapses in on itself -chest wall moves outward because its elastic recoil is no longer opposed by coupling to the inward pulling forces of the lungs
when inspiratory muscles, diaphragm, and external intercostals relax, this decreases what in the thoracic cavity?
-the anteroposterior, vertical, and lateral diameters of the thoracic cavity
During each breath, the pressure gradients move ____ liter of air into and out of the lungs.
0.5
Two _____ forces promote lung collapse
inward -These want lungs to assume the smallest possible size
the ______ the diameter of an airway, the less the airway resistance and the greater the flow
larger
For air to flow into the lungs, the pressure in the alveoli must be _______ than atmospheric
less
Just like blood flow through the circulatory system, air flow depends upon:
pressure difference and resistance
Elasticity of chest wall does what to thorax?
pulls thorax outward -This outward pull is coupled to the lungs by the pressure in the sealed intraplerual space.
Surface tension of alveolar fluid _______ alveolar size
reduces -The water lining the alveolar surface in the lungs doesn't want to pull apart when they are slightly inflated, or are inflating
Boyle's law
states that volume and pressure are inversely related. -Thus if there is a decrease in a container's volume, there will be an increase in the pressure within. V ∝ 1/P P1V1 = P2V2
Physiological (total) dead space
sum of anatomical and alveolar dead space
respiratory volumes
tidal volume (TV), inspiratory reserve volume (IRV),expiratory reserve volume (ERV) and residual volume (RV)
respiratory capacities
total lung capacity (TLC), vital capacity (VC), inspiratory capacity (IC), functional residual capacity (FRC)
5 steps to inhalation
1. Inspiratory muscles contract (diaphragm descends; rib cage rises). 2. thoracic cavity volume increases 3. lungs are stretched; intrapulmonary volume increases. 4. Intrapulmonary pressure drops. 5. r (gases) flows into lungs down its pressuregradient until intrapulmonary pressure is 0 (equal to atmospheric pressure).
how much of the tidal volume reaches the respiratory zone? what happens to the rest
70%. the other 30% remains in the conducting zone (called the anatomic dead space).
at sea level air pressure is
760 mmHg = 1 atmosphere
transpulmonary pressure
=(P_pul - P_ip) -Keeps lungs open -Greater transpulmonary pressure larger lungs
surfactant
A mixture of phospholipids and lipoproteins present in the alveolar fluid
what muscles are required in active exhalation?
Abdominals -Moves the inferior ribs downward and compresses the abdominal viscera -Forces the diaphragm superiorly Internal intercostals -Pulls the ribs inferiorly
what can obstruct diaphragm flattening?
Advanced pregnancy, excessive obesity, and confining abdominal clothing
tidal volume
Amount of air inhaled or exhaled with each breath under resting conditions
expiratory reserve volume
Amount of air that can be forcefully exhaled after a normal tidal volume expiration
inspiratory reserve volume
Amount of air that can be forcefully inhaled after a normal tidal volume inspiration
obstructive disorders
Any pathological condition that narrows, or obstructs, airways
Pressure is measured as
Force applied per unit Area, P = F/A.
what is active exhalation and when does it occur?
Forceful exhalation -Playing a wind instruments, yelling, or exercise
compliance
How easily the something stretches
anatomical dead space
No contribution to gas exchange
Pneumothorax
air, or liquid (blood or Interstitial fluid), in pleural cavity caused by either wound in parietal or rupture of visceral pleura
The surface tension of alveolar fluid is found at when air tries to fill the alveoli, the fluid on the alveoli doesn't want to pull away from itself and produces an inward pull resisting expansion Causes the alveoli to assume the smallest possible diameter Accounts for 2/3 of lung elastic recoil. If unopposed, this force would cause the alveoli would close with each expiration and make our "Work of Breathing" insupportable
all air-water interfaces
what is the most important muscle for inhalation (inspiration)?
diaphgram
In obstructive diseases (asthma, COPD, chronic bronchitis, emphysema) FEV1 is ________ because of increased airway resistance to expiratory flow
diminished -Harder for air to be exhaled thus less air comes out in 1 second when compared to normal individual
If the bronchioles dilate even a little, the resistance _________
drops by a power of 4
how is Infant Respiratory Distress Syndrome (IRDS) treated?
by using continuous positive air pressure (CPAP) breathing machines - increases pressure of air going into the lungs - and synthetic surfactant until infant begins producing its own
Low pulmonary compliance
they resist expansion - harder for inflation
Elastic recoil of lungs ______ lung size
decreases
air flows from ____ to _____ pressure
high to low
Intrapleural pressure
(P_ip) -Pressure in pleural cavity -Changes when breathing
Intrapulmonary (intra-alveolar) pressure
(P_pul) -Pressure in alveoli -Changes when breathing -Always eventually equalizes with P_atm
pressures role in airway resistance
*As lungs expand during inhalation, the bronchioles enlarge bc the are being pulled outward in all directions. -This decreases resistance to flow in to the lungs *During exhalation, the increase in pressure compresses the bronchioles -This increases resistance to flow out of the lungs
passive exhalation begins when
- inspiratory muscles relax -The diaphragm relaxes and begins to rise superiorly and regain it's dome shape -external intercostals relax and the ribs are depressed
FEV1 (forced exp volume)
-Amount of vital capacity one can forcibly expel in 1 second -In healthy adults this should be approximately 75-80%
when the anteroposterior, vertical, and lateral diameters of the thoracic cavity are decreased what happens?
-Decreases lung volume - increase in alveolar pressure above that of atmospheric -Air flows from high (lungs) to low (external environment) pressure
Infant Respiratory Distress Syndrome (IRDS)
-Deficiency of surfactant in premature infants -Alveoli collapse due to high surface tension
diaphgram
-Dome-shaped skeletal muscle innervated by the phrenic nerve
Accessory muscles of inhalation role
-Involved in active inhalation -These assist in increasing thoracic volume during exercise or deep, forceful inhalations -Do not really contribute quiet breathing
Earth's atmosphere is composed of what gases?
-Nitrogen (N2) : 78% -Oxygen (O2) : 21% -Carbon Dioxide (CO2): 0.04% -Water Vapor: variable, but on average around 1%
Passive exhalation
-Normal exhalation during quiet breathing -Called passive because no muscular contractions are involved
passive exhalation results from inward forces:
-The elastic recoil of the chest wall and lungs -the inward pull of the surface tension of the alveolar fluid
Lung compliance dependent upon 2 factors
1.Elasticity -Lungs have a high amount of elastic fibers -Allows for greater stretch and recoil 2.Surface tension
3 steps of respiration
1.Pulmonary ventilation 2.External (pulmonary) respiration 3.Internal (tissue) respiration
Differences in air pressure drive airflow, but 3 other factors also affect the ease with which we ventilate:
1.The surface tension of alveolar fluid 2.Compliance of the lungs 3.Airway resistance
total lung capacity
Maximum amount of air contained in lungs after a maximum inspiratory effort: TLC = TV + IRV + ERV + RV
vital capacity
Maximum amount of air that can be expired after a maximum inspiratory effort: VC = TV + IRV + ERV
inspiratory capacity
Maximum amount of air that can be inspired after a normal tidal volume expiration: IC = TV + IRV
Nonrespiratory Air Movements
May modify normal respiratory rhythm Most result from reflex action; some voluntary
atmospheric pressure
P_atm
Respiratory pressures (those in the cavities used for breathing) are described relative to what? what are the negative positive and zero pressues?
P_atm (760) Negative respiratory pressure = less than Patm Positive respiratory pressure = greater than Patm Zero respiratory pressure = Patm
changes in Intrapleural pressure during inhalation and exhalation:
Pleural cavity pressure becomes more negative as chest wall expands during inspiration. Returns to initial value as chest wall recoils.
changes in intrapulmonary pressure during inhalation and exhalation:
Pressure inside lung decreases as lung volume increases during inspiration; pressure increases during expiration.
Accessory muscles of inhalation
Sternocleidomastoid -Elevates the sternum Scaline -Elevates the first two ribs Pectoralis minor -Elevates ribs 3-5
restrictive disorders reduce
TLC due to disease or fibrosis VC, TLC, FRC, RV decline
T OR F: Because the lungs are in separate pleural cavities, one may collapse without interfering with the function of the other
TRUE
Smooth muscle's role in resistance
The diameter of airways is regulated by smooth muscle tone which is dependent upon parasympathetic and sympathetic interaction
functional residual capacity
Volume of air remaining in the lungs after a normal tidal volume expiration: FRC = ERV + RV
Inward pull being opposed by outward pull creates
a lesser pressure between the lungs and the thoracic wall (P_ip) when compared to pressure in the lungs (P_pul)
intrapleural pressue (P_ip) should always be a __________ pressure.
a negative pressure (<Patm and <Ppul) in order to prevent lung collapse
Ventilation, or breathing, is made possible by changes in pressure at the
alveoli relative to the atmospheric pressure -The changes in pressure are due to changes in thoracic volume.
Forced expiratory volume (FEV)
amount of gas expelled during specific time intervals of VC
barometer
an instrument that measures atmospheric pressure.
types of obstructive lung diseases include
asthma, bronchitis, chronic obstructive pulmonary disease (COPD), emphysema, cystic fibrosis, etc.
Just before each inhalation, the pressure inside the lungs is equal to
atmospheric pressure (760mmhg)
besides obstructive disorders, Airways can also become blocked via
collapse of bronchioles, alveoli, or build-up of excess mucous
boyles law applies to
containers with changeable volume - like our thoracic cage.
examples of non respiratory air movements
cough, sneeze, crying, laughing, hiccups, and yawns
2nd most important muscles for inhalation?
external intercostals
True or false: to understand the mechanics of ventilation and respiration, we need to have a basic understanding of 4 of the 5 common gas laws.
false its 3 out of 5 laws
contraction of the diaphragm causes it to
flatten. This increases the vertical volume of the thoracic cavity
Although P_ip is always less than P_pul, P_ip can sometimes exceed P_atm Although Pip is always less than Ppul, Pip can sometimes exceed P_atm during
forced exhalation such as a cough
gas laws apply equally to what type of gases
gases of the atmosphere, the gases in our lungs, the gases dissolved in the blood, and the gases diffusing into and out of the cells of our body.
In exhalation The pressure in the lungs is ___________ than that of the atmosphere
greater
obstructive pulm. disease
increased airway resistance *TLC, FRC, RV may increase
bronchiole constriction does what to resistance?
increases it by power of 4
This decrease in alveoli pressure is accomplished by
increasing the volume of the lungs through mechanical coupling to a change in thoracic volume
pulmonary ventilation consists of
inhalation and exhalation.
spirometer
instrument for measuring respiratory volumes and capacities
The change in volume of the diaphragm is transferred to the lungs via the
intrapleural cavity and the pressure within it. Intrapleural pressure becomes slightly more negative generating a greater outward pull on the lungs This causes the lungs to expand thus increasing their volume and decreasing the pressure at the alveoli below that of atmospheric
At high altitudes, the atmospheric pressure is _______ ; descending to sea level, atmospheric pressure is __________.
less, greater
High pulmonary compliance
lungs and chest wall are easily expanded - easier for inflation
If P_ip = P_pul or P_atm then
lungs typically collapse
alveolar dead zone
non-functional alveoli due to collapse, poor perfusion, or obstruction
Spirometry can distinguish between
obstructive pulmonary disease & restrictive disorders
Negative P_ip is caused by
opposing forces
To exhale, the pressure difference is _______ that of inhalation
opposite
One _______ force tends to enlarge lungs
outward
how is pneumothorax treated?
removing excess intrapleural air/fluid with chest tubes; restores negative pressure--> lung re-inflates
restrictive disorders
restrict lung expansion resulting in a decreased lung volume, an increased work of breathing, and inadequate ventilation that can lead to reduced blood oxygenation
__________ disorders decrease compliance of lungs
restrictive disorders *Pulmonary fibrosis -Deposition of scar tissue in the lungs -Scar tissue not very elastic *Deficiency in surfactant *Pulmonary edema (excess fluid in the lungs) *Impedance to expansion -E.g. Ventilatory muscle paralysis, broken ribs, obesity
air pressure varies greatly depending on
the altitude and the temperature.
surfactant reduces
the alveolar fluid surface tension below the surface tension of pure water -Allows for easier inflation of the alveoli and helps prevent alveolar collapse during exhalation
Amount of diaphragm contraction (flattening) correlates to
the amount of air entering the lungs * More flattening -> increased volume (thoracic and lungs) -> greater pressure difference -> increased filling to equalize
in diaphgram air rushes in from the higher external atmospheric pressure to the lower internal alveoli pressure causing what to happen?
the lungs to fill in an effort to equalize the two pressures. -This is responsible for about 75% of air that enters the lungs during resting (quiet) breathing
Pulmonary ventilation
the movement of air between the atmosphere and the alveoli of the lungs
The pressure we feel on the surface of the earth is
the weight of the gasses in our atmosphere
T OR F : Breathing out is also due to a pressure difference
true
true or false: the atmosphere exerts a significant force on every object on the planet
true (bc the atmosphere has a mass and weight)
TRUE OR FALSE: Plural fluid helps limit friction between lungs and thoracic wall, but fluid amount must be kept to a minimum
true. Excess fluid is pumped out by lymphatics If accumulates ---> positive Pip pressure ---> lung collapse
During inhalation, the ribs move
upward and outward like the handle on a bucke
Polar water molecules are more strongly attracted to each other than gas in an air, what does this mean?
when air tries to fill the alveoli, the fluid on the alveoli doesn't want to pull away from itself and produces an inward pull resisting expansion. This Causes the alveoli to assume the smallest possible diameter. Accounts for 2/3 of lung elastic recoil. -If unopposed, this force would cause the alveoli would close with each expiration and make our "Work of Breathing" insupportable
