Mechanics Of Breathing 😮💨 Flashcards
Respiration refers to 2 things
- Cellular respiration: binding glucose with oxygen to produce ATP within the cell
- External respiration: movement of gases from the external environment into cells of the body
Ventilation includes
Inspiration and expiration which is responsible for the bulk flow of air
Primary functions of the respiratory system includes
- Gas exchange (oxygen and carbon dioxide) between the external environment and body
2. Homeostatic regulation of pH to retention/excretion of CO2.
*(When you hearCO2 think pH) - Protection from inhaled pathogens and irritants
- Vocalization
What is another important function of the respiratory system
Conditioning the inhaled air by humidifying and warming it to match the internal conditions. Example air outside the body is 24°C and 30 to 50% humidity, air in the lungs is 37 degrees Celsius and 100% humidity. This is best that she by inhaling through the nasal cavity with help of the nasal concha that swirl the air
What are some similarities in the respiratory system with the cardiovascular system
- Air, like fluids flow from areas of high pressure to low pressure
- A muscular pump creates the pressure gradient
- Resistance to flow is primarily influenced by the diameter of the tubes
The conducting portion of the respiratory tract
Carries air into the lungs towards the alveoli in the respiratory portion where gas exchange happens. The conducting portion does not take part in gas exchange as such is considered anatomic dead space
The lungs are located within
Pleura sacks in the thoracic cavity.
Outside the lungs is covered by
Visceral pleura
The pleural cavity’s are lined with
Parietal pleura
Between the plural of membranes is the plural space that is filled with
Pleural fluid about 25 to 30 ML‘s that keeps the two functionally stuck together
Respiratory muscles pull on the
Parietal pleura which in turn pulls on the visceral pleura and opens the lungs creating a low pressure space and air flows into the lungs
Respiratory epithelium is made of
Pseudostratified ciliated columnar epithelium cells and goblet cells
A thin layer of
Saline fluid covers the epithelium, with a mucus layer over that. Together these trap in hell dust/pathogens and move them towards the pharynx termed mucociliary escalator. For swallowing or spitting out.
The Saline layer is created by
Movement of chlorine ions by epithelial cell transporters/channels, sodium diffusion, and osmosis.
Without the Saline layer
The escalator does not function and is the cause of cystic fibrosis
Alveoli are surrounded by
- Capillaries carrying blood to exchange gases.
- Elastic and collagen connective fibers that help prevent over inflation (they provide elastic recoil).
- There is not muscle around Alveoli therefore they do not constrict, like there is around bronchioles. 
Alveoli are made of
Two simple squamous epithelium cells types, plus free macrophages that clean up alveolar tissue
•type 1 and type 2
Type one alveolar cells
95%, make up the blood air barrier and allow gas exchange
Type 2 alveolar cells
5% produce surfactant that reduces surface tension within Alveoli and helps keep them inflated/open
The blood air barrier is composed of
Type one alveolar cells and endothelial cells simple squamous epithelium of capillaries, connected by a thin basement membrane. All three layers together are about 0.5 micro meters thick which allows very easy and fast diffusion across it.
(Compare mature erythrocytes are seven micro meters diameter)
Air is a mixture of
Gases and water vapor that follow similar rules as the flow of liquids
Table 17.1 p. 542
Pressure is measured in
Millimeters of mercury, tour, or centimeters of water or kilopascals
We will use mmhg
At sea level normal atmospheric pressure is (Patm)
760 mmHg. As a convention this value is scaled 0 mmHg for simplicity. 
Dalton’s law describes
The relationship of partial pressure (Pgas) of gases in a mixture. The contribution of each individual gases pressure in a mixture of the total pressure.
Partial pressure is related to
The concentration of the individual gas and changes with concentration of water vapor in the mixture 
Fig. 17.6c p. 541
Example air is composed of 21% oxygen at sea level with dry air what is the partial pressure of oxygen
760 mmHg x 0.21 = Po2 of 160mmhg
(In dry air at sea level)
However if there is water vapor it needs to be
First be subtracted from the atmospheric pressure (Patm)
Example at 100% humidity 25°C
PH2O = 24mmHG: (760mmHG-24mm HG) x 0.21= Po2 of 155mm HG.
***ask
At 100% humidity
Temperature is the primary determinant of water vapor pressure
Partial pressure applies individually to
EACH each gas, so our bodies can exchange oxygen based on the partial oxygen pressure Po2, independent of, for an example CO2 which is regulated by its partial pressure PCO2
Boyles law describes
The changes in a gases pressure as the volume of the gas changes, it is an inverse relationship p1v1=p2v2
Fig. 17.6b p. 541
Boyles law example
1 L of air in a container it has Pair equals 100 MMHG, if volume increases to 2 L then P air equals 50 MMHG, if volume decreases to 0.5 L, the P air equals 200 MMHG
Boyles law is relevant because at higher altitudes
The volume of air increases so the total pressure decreases, but the concentration of gases that make up air do not change just the partial pressure of the gases which is one of the reasons why it’s harder to get oxygen at elevation
Barometric pressure has
No virtually effect on the partial pressure of water vapor
As it relates to the bulkk flow of air in and out of the lungs the movement of air goes passively from
High pressure to low pressure
As lung volume increases
Pressure inside the lungs decrease (compared to outside) > causing airflows into lungs 🫁 
As lung volume decreases
Pressure inside the lungs increases (compared to outside) > causing air to flow out.
Lung function maybe analyze through
Pulmonary function test a.k.a. spirometry which measures various volumes associated with ventilation
Tidal volume (Vt)
Amount of air moved during normal resting breath about 500 ML
Inspiratory reserve volume (IRV)
Air in a forced inhalation beyond title volume about 3000 ML
Expiratory reserve volume (ERV) 
 Air in a forced exhalation about 1100 ML
Adding these three volumes together gives (tidal volume, inspiratory reserve volume, expiratory reserve volume)
The vital capacity ( VC )
Because the lungs never fully empty the amount of remaining air after forced exhalation is called the
Residual volume (RV) is about 1200 ML
(VC) vital capacity and (RV) residual volume added together provide the
Total lung capacity TLC
These simple measurements can be used to help early signs of lung diseases such as COPD emphysema chronic bronchitis and asthma
Airflow requires a
Pressure gradient and flow decreases with resistance

Flow is equal to
Q= pressure change/ R
Respiratory muscles expand the lungs
Diaphragm contraction accounts for 60 to 75% of expansion, scalene, external intercostals and sternocleidomastoid contraction elevate the rib cage and account for the remaining 25 to 40%
As the lungs expand air passively follows 
The pressure gradient that is created in the alveoli but lags slightly simply due to the fact that it takes time for the air to move in and out of the lungs
The intrapleural pressure remains
Negative (relative to atmospheric pressure) throughout the ventilation cycle: -3mmHg between breaths and up to -6mmHg (-8mmHg during forceful inhalation)
The negative pressure between the plural membranes is what allows
The pulling from the outside by muscles to expand the lungs, muscles pull the parietal pleura which is functionally stuck to the visceral pleura through negative pressure and expands the lungs
Pneumothorax is a condition when
- The negative intrapleural pressure is removed usually through a puncture wound that allows air into the intrapleural space but can also happen from with in the lung if the tissue ruptures.
- as the pride all of the syrup pleura no longer have a functional attachment the lungs collapse under its own weight/recoil. To fix this the intrapleural air needs to be sucked out and the puncture sealed in order to reestablish the negative intrapleural pressure
What are two opposing forces that interact when considering the work/energy required to ventilate the lungs
Compliance and elastance
Compliance
Refers to the ability to stretch, with higher compliance it takes less energy to stretch and expand the lungs.
Compliance is equal to change in volume/change in pressure.

So that a change in volume is influenced by the energy/pressure required to cause that volume to change.
What percent of the bodies energy budget is spent on routine breathing in order to overcome lungs compliance
3 to 5% which would be even higher without the help of surfactants.
Pulmonary fibrosis is a condition in which Alviola develop stiffness loose compliance making it harder to fill them with air
Elastance
Refers to the ability to recoil after being stretch the inverse of compliance so if the lungs have high compliance the elastance will be low.
• compare the ease of blowing air into a plastic veggie bag which does not require much when you stop blowing, to a rubber balloon which is less compliant hearted and play but stretches back much easier.
*Emphysema is a condition in which lungs or lose elastance so they do not require as easily making it harder to breathe
The law of Laplace
P=2T/r
P is pressure T is surface tension R is radius.
*If the radius is small and surface tension is constant the pressure required to inflate it increases.
*Small Alveoli are harder to inflate the larger ones
Type to alveolar cells produce
Surfactant surface active agents, a mix of proteins and phospholipids that help break down the surface tension and make the Alviola easier to inflate.
Without surfactant the energy required to breathe increases dramatically example and premature babies bodies do not begin producing surfactant mortality rate is up to 50% without treatment
Resistance is the other component affecting airflow defined by
Poiseuilles law: R = Ln/r4.
L is length , n is viscosity, r as radius.
Length and viscosity do not change much unless it’s really humid it so that leaves the airway radius or diameter as the main determinant one considering airflow in and out of the lungs
In the upper respiratory tract nasal passages trachea and bronchi
Physical obstructions can affect airflow, mucus dust/dirt
The bronchioles in the lower respiratory tract have
Smooth muscle around them and may be constricted bronchoconstriction to protect your lungs from inhaled particles or relaxed bronchodilation to meet metabolic means
Paracrine signals exert minute to minute control over construction/dilation primarily in response to
Increase in CO2> smooth muscle relaxation> Bronchodilation> increase ventilation
Histamine has the
Opposite affect causing bronchoconstriction in response to allergic reaction or tissue damage
ANS control is mainly through
- Parasympathetic input on muscarinic receptors which exert tonic bronchoconstriction.
- Sympathetic input directly influences through circulating epinephrine not directly through norepinephrine which stimulates beta 2 receptors on smooth muscles causing bronchodilation
Local control mechanisms attempt to match
Ventilation and perfusion
Perfusion at the Alviola changes with
Activity levels depending on pressure in Vessels capillaries can collapse were not perfused
When alveolar oxygen decreases and carbon dioxide increase is detected locally
Blood is diverted through vasoconstriction to other capillaries where alveolar oxygen is higher. At the same time these levels of oxygen and carbon dioxide cause bronchodilation to increase oxygen and decrease carbon dioxide and help alleviate the problem
WTF
Note that the response by systemic capillaries are the
The exact opposite as pulmonary capillaries
The main control of these affects is through local paracrine signals. neural autonomic nervous system controls has some but limited influence
