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Phys Exam 3 lungs


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Where does gas exchange occur?
In alveoli
movement of air from the external environment into the alveoli
refers to movement of air from the alveoli to the external environment
what conducts air between the external environment and the alveoli?
describe airway composition
a continuous branching network of tubes that terminate in the alveolar sacs
How many generations of branching occur in the airways?
What does upper airway consist of?
nose mouth, pharanx, larynx
What does larynx lead into?
trachea which divides into multiple generations of bronchi
walls of trachea and bronchi are composed of what? what is its function?
cartilage which allows structural support and helps keep the airway open
first airways that do NOT contain cartilage
bronchioles. This is the level alveoli appear at
Where do terminal airways end?
at alveoli clusters
two functional zones of respiratory tract
1. conducting zone- it begins at the trachea and ends ant the begining of the respiratory bronchi. NO gas exchange occurs here.

2. Respiratory Zone- extends from the repiratory bronchioles down through the alveoli. ALL gas exchange occurs here.
In what zone does gas exchange occur?
Respiratory Zone
What surrounds alveoli?
rich supply of blood vessels so respiratory gases like CO2 and O2 are rapidly exchanged across the repiratory membranes
3 types of protection respiratory system has from particulate matter
1. Cilia
2. mucus
3. water fluid
4. macrophages
Describe cilia location and function in respiratory tract
epithelial surfaces of airways to the end of the repiratory bronchioles contain cilia that beat upward toward the pharanyx. These epithelial cells also have glands that secrete mucus. mucus traps particulate matter and is moved by cilia toward pharynx and swallowed.
Function of watery fluid secreted by epithelial surfaces of airways
mucus rides on it. Without the watery substance mucus layer becomes thick and dehydrated.
Cystic fibrosis
defect in the chloride channels. no watery fluid for mucus to ride on so causes drying
When are macrophages and cilia drastically impaired?
By smoking
hollow sacs whose open ends are continuous with the airway lumens. Usually lined in single, continuous layer with type I and interspered with Type II
Type I alveoli
lined continuous in single layer. Most alveoli
Type II alveoli
interspersed in monolayer. They produce surfactant
Total surface area available for gas exchange
70 squarre meters
repiratory membrane
entire pathway over which oxygen and carbon dioxide must travel. It consists of the alveoli wall epithelial cells, the interstiitial fluid, and the capillary wall. these are all v. closely related so that gas exchange can occur
What promotes rapid exchange of the repiratory gases between the alveoli and the blood?
combination of large surface area and a short diffusion path
Where are lungs?
in closed thorax
What surrounds lungs?
pleural sac, a thin sheet that consists of two membranes really close to each other (inner and outer membrane)
inner membrane of pleural sac
attached to thesurface of lung by connective tissue
Outer membrane of pleural sac
attached to the inner thoracic wall and the diaphragm by connective tissue
what seperates the inner and outer membrane of the pleural sacs?
intrapleural fluid to lubricate the pleural surfaces. changes in the hydrostatic pressure of this fulid are directly related to the movements of the lungs and the thoracic wall
Are the pleural sacs for each lung the same?
no the pleural sac for each lung is seperate
are inner and outer pleural membrane attached?
NO. they are seperated by intrapleural fluid
steps of respiration
1. ventilation: exchange of air between atmosphere and alveoli by bulkflow.
2. exchange of O2 and CO2 between alveolar air and blood in lung caps by diffusion
3. transport of O2 and CO2 through pulmonary and systemic circulation by bulk flow
4. Exchange of O2 and CO2 between blood in tissue caps and cells in tissue by diffusion
5. cellular uses O2 and makes CO2
What causes pressure gradient at periphery?
Cells use Oxygen and produce carbon dioxide. so puts hi CO2 and low O2 in blood that ways after blood goes through right heart (lungs) O2 will have gradient to move in and CO2 will have gradient to move out to alveoli
exchange of air between the external environment and the alveoli
Bulk flow equation
F = (Patm - Palv)/(R)

reistance to flow by lungs in v. low so the flow has lo pressure
What is the MOST important factor for determing airway resistance
diameter or radius of the air passages.

remember that resistance is inversely proportional to the fourth power of the radius
Boyles law
at constant temp, pressure exerted by fixed number of gas molecules varies inversely with the volume of the container.

Ex: Increase in volume of container decreases the pressure of the gas.

decrease vol. increase press.
increase vol. decrease press.
What alters the pressure gradient between the alveoli and the external environment?
changes in alveolar pressure do to volume of lungs changing. Air flows into or out of the alveoli depending on direction of pressure gradient
what does it depend on for air to go in or out of alveoli?
Pressure gradient
transpulmonary pressure
measured between inside and outside of the lungs (NOT between the alveoli and outside the chest) Pal-Pip
Inside pressure
pressure of air in the alveoli (Palv)
Outside pressure
pressure of the intrapleural fluid (Pip)
Transpulmonary equation
alveoli P - intrapleural f. P
For air to get into system what must have most pressure?
For air to get in system atmospheric pressure must be greater in atmosphere than in intrapelural fluid
What happens to lungs at the end of expiration?
the lungs expand bc of the positvie transpulmonary pressure is exactly balanced by the elastic recoil force of the chest wall
What allows diaphragm and inspiratory intercostals to contract?
neurally induced. controlled by midbrain pacemaker cells
chain of events that happens when the diaphragm and inspiratory intercostals contract
thorax expands

Pip becomes subatmospheric bc vol increases so P decreases

Increase in traspulmonary P

Lungs expand

Palv becomes subatomospheric bc pressure decreases when vol. increases

Air flows into the alveoli
is inhalation active or passive?
Inhalation is active while exhalation is passive
inspiration process
neurally induced contraction of the diaphragm and inspiratory intercostal m. between the ribs which increase vol. in thorax, the decrease in vol. increases transpulm. P. Lungs expand. Expanded lungs increase vol of alveoli and decrease the P causing movement of air into lungs
Expiration process flow chart
diaphragm and inspiratory intercostals stop contraction

chest wall recoil inward

Pip moves to preinspiration value

Transpulmonary pressure moves beack toward preinspiration

lungs recoil to reg. size

air in alveoli is compressed

Palv becomes greater than Patm

Air leaves lungs
Expiration proccess
expiration is initiated by relaxation of diaphragm and inspiratory intercostal m. the chest wall is no longer being pulled out so vol. decreases due to elastic recoil

transpulm. P decreases bc vol of lungs decreases

vol of alveoli decrease and pressure in alveoli increase

increase in alveolar P increases the P gradient between the alveoli and the environment and air leaves lungs
Lung compliance
magnitude of the change in lung volume produced by a given change in the transpulmonary pressure
Compliance equation
Change in lung vol./Palv-Pip
What does lo lung compliance meant
greater than normal transpulmonary pressure must be generated to produce a gain amount of lung expansion. Basically you need a greater Pip to increase the work of breathing
2 determinants of lung compliance
1. elasticity of connective tissue

2. alveolar surface tension
Purpose of surfactant
reduces the surface tension forces within the alveoli therefore increasing the lung compliance
What enhance secretion of surfactant by type II cells?
Deep breaths
What is airway resistance determined by
physical, neural, and chemical factors.
What is airways resistance normally/
Very low and therefore there a small pressure gradient can cause large movement of air
What does transpulmonary pressure do to airways?
distends the airways mainly those without cartilage and reduces the resistance to air flow
lateral traction
produced by elastic connective tissue fibers that are attached to the exterior of airways. The forces exerted by there fibers help to destend the airways and further reduce resistance of airway.
What neural factors effect airways?
1. epinephrine relaxes airway smooth m. by binding to beta receptors and reduces airway resistance

2. Leukotrienes produced during inflam. contract airway smooth m. and increase airway resistance
diseae where airway smooth m. contracts strongly and increases resistance. treat with anti inflam drug (glucocorticoids) to reduce inflam or use bronchiodialtors to reduce excessive smooth m. contraction
chronic obstructive pulmonary disease (COPD)
causes difficulties with ventilation and with oxygenatin of the blood. v. common with smokers
is increased smooth m. constriction responsible for COPD?
NO it is due to ventilation
2 types of COPD

chronic bronchitis
results from destruction of alveoli, enlarged alveoli air space which decrease SA, and loss of pulmonary caps. It is thought that lung produces proteolytic enzyme to destroy elastic tissue
Chronic Bronchitis
caused by excessive mucus production in bronchi and chronic inflam changes in small airways
How many exclusive volumes can total lung vol. be divided into?
Tidal vol
(resting vol) volume of air moved in and out of lungs during quiet breathing. Usually about 500 mL
inspiratory reserve vol (IRV)
additional vol of air that can be inspired by maximum exertion of the inspiratory m. following normal inspiration
Expiratory reserve volume (ERV)
additional vol of air that can be exhaled by maximal contraction of the expiratory m. following a normal expiration
residual vol.
amount of air that is left in the lungs at the end of a max expiration.

Cannot get all the air out of lung, EVER! So air remains in lungs even after expiration
inspiratory capacity
tidal vol + inspiratory
reserve vol.

it is amount of air that can be inspired from the end of a normal expiration
Functional residual capacity
expiratory reserve vol
residual volume

amount of air that remain in the lungs at the end of normal expiration
two capacities that make up lung
inspiratory capacity
functional residual capacity
vital capacity
total amount of air that can be inspired after performing a maximal expiration. Total amount of air that can be physiologically controlled

expiratory reserve vol + tidal vol + inspiratory reserve vol

basically its the max expiration to the max inspiration
lung vol that make up the total lung capacity
inspiratory reserve vol
+ resting tidal vol + expiratory reserve vol + residual vol
forced expiratory volume in 1 sec (FEV1)
amount of air an indiviual can exhale in one sec by max respiratory exertion following a max inspriation. Imporant clinically to measure as a percentage to vidal cap (FEV1/Vital Cap)
Normal percentage of FEV1
FEV1 in obstructive lung disease
way less than normal 80% due to narrowing or obstuction or respiratory airways.

These people have barrel chest bc air is traped in lung and have hi resistance with expiration
2 types of pulmonary disease
obstructuve lung disease

restuctuve lung disease
FEV1 with restuctive lung disease
airway resistance is normal by respiratory movements are impaired. Vital capacity is reduced but normal ratio of FEV1 to vital cap.

Seen in people w/ disease of diaphragm or inspiratory m.
minute ventilation
total amount of air moved into and out of lungs over a one min. period
minute vol calculation
tidal vol X respiratory rate
problem with minute vol calculation
it does not tel us alveolus ventilation
volume in conducting airways
about 150 mL where no gas exchange takes place. so this is known as atomic dead space
alveolar ventilaiton
amount of fresh air that moves into the alveoli during a one min period
alveolar ventilation calculation
(tidal vol - dead space)
respiratory rate
How shoud dr find efficacy of repiratory activity?
focus on alveolar ninute ventiation.
Alveolar dead space
vol of air contained in alveoli that have little or no blood supply.
physiological dead space
total dead space. which is the sum of the anatomical dead space and the alveolar dead space
air in dead space at the end of inspiration
fresh air
air in dead space at the end of expiration
alveolar air
In steady state what does O2 consumed by tissues equal?
vol of oxygen added to blood in the lungs. Same for CO2 produced by tissue is equal to rate at which CO2 leaves the blood and enters the lungs
respiratory quotient (RQ)
CO2 production/ O2 consumption
RQ carbs
1 so O2 production = CO2
RQ fat

CO2 producion/O2 consumption
is 7/10
RQ protein
RQ for mixed diet
what is presure exerted by a agas on the walls of its containe due to?
random motion of gas molecules
what is random motion of gas molecules that cause pressure on a gas equal to?
temp and conc of gas mol.
Dalton's law
in mix of gases the pressure exerted by one gas is independent of the pressure exerted by any of the other gases in the mixture. The total pressure of a gas mixture is the sum of the individual partial pressure of the seperate gases
Atmospheric air composition
79% Nitrogen
21% oxygen
henrys law
amount of particular gas dissolved in the liquid is directly proportional to the partial pressure of that gas in the space above the liquid
what will happen if the partial pressure of a gas is higher is the liquid phase than in the gas phase?
gas wil diffuse out of the liquid phase into the gas phase
What is partial pressure of a gas is higher in the gas phase than in the liquid phase?
gas will diffuse into the liquid
Oxygen pressure in atomospher and alveoli
in atmosphere 160 mmHG
in alveolar 105 mmHG
pressure of CO2 in atomosphere and in alveoi
atmosphere = 0.3
alveoli = 40
Pressure of water in atmosphere and in alveoli
atmosphere = 0
alveoli = 46

comes from air and air gets humidified in the lungs
pressure on N2 in atmosphere and in lungs
atmospher 600 mmGH
alveolli is 569 mmHg
What happens to O2 pressure in alveolus if alveolar ventilation decrease?
it will decrease
What happens to alveolar O2 pressure if cellular O2 consumption is increased?
it will be decreased
Factors that determine the value of alveolar CO2 pressure
rate of alveolar ventilation

rate of cellular CO2 production
what happens to alveolus CO2 pressure if alveolar ventilation is decreasedd?
It increases
What happens to alveolus CO2 pressure if rate of production of CO2 by cells increases
it will increase
What is alveolar O2 pressure determined by at any particular atmospheric O2 pressure?
ratio of O2 consumption by tissues to alveolar ventilation
What is alveolar CO2 pressure determined by at any particular atmospheric CO2 pressure?
ratio of CO2 production by tissues to alveolar ventilation
increase in ratio of CO2 production to alveolar ventilation that causs increase in alvolar CO2 pressure above normal value of 40 mmHg
decrease in ratio of CO2 production to alveolar ventilation that causs decrease in alvolar CO2 pressure below normal value of 40 mmHg
In normal circumstances, where does O2 and CO2 equilibrate?
between the alveoli and pulmonary caps before the blood leaves the caps
what does effient use of the lungs to supply oxygen to the blood in pulmonary caps and remove CO2 depend on?
ensureing that alveoli have good blood supply and are well ventilated. Any mismatch is called a ventilation-perfusion ratio
If alveoli is not well ventilated, what is optimum blood supply?
it must be reduced as well
what happens when alveolus is under ventilated?
lack of oxygen in the alveolus and surrounding tissue casue vasoconstiction of pulmonary bv in that region in order to maintain normal ventilation perfusion ratio
What does ventilation perfusion abnormalities cause?
lower oxygen pressure in the systemic arterial blood. Elevation of CO2 pressure in the systemic arterial blood too sometimes
2 forms of oxygen in arterial blood
dissolved in blood plasm

reversibly bound to hemoglobin contained in the RBS
% of total O2 in arterial blood that is dissolved plasma
3% bc its low solubility in water so majority of O2 (97%) is bound to hemoglobin and carried.
How many oxygens can one hemoglobin carry/
percent saturation of O2
amount of O2 bound to Hb/ maximal capacity of Hb to bind O2
x 100
oxygen hemolglobin dissociation curve
relationship between the oxygen pressure in arterial blood and percent saturation of Hb.

S shape curve steepest portion between partial pressure of O2 of 10-60 mmHg.

plateus at O2 pressure of 60 mmHg
What initiates inspiration?
action potentials in motor nerves to inspiratory m.
only time expiratory m. are activated by action potentials
forced expiration
where is control of AP for respiratory m.?
in medulla oblongata. medulary inspiratory neurons provide the rhythmicinput to motor neurons
What is rhythmic activy of respiration result of?
interactions w/ other medually neurons and intrinsic pacemaker potentials in inspiratory neurons themselves. these fire to start inspiration process
what modulateds output of inspiratory neurons and may terminate inspiration by inhibiting the nuerons?
the lower pons (apneustic center)

The upper pons (pneumotaxic center) modulates the lower pons
purpose of pulmonary stretch receptors
limit inspiration. safety mechanism so you dont over inflate the lungs. ONLY IMPORTANT WHEN TIDAL VOL IS LARGE LKE W/ EXCERCISE
What can be changed to control ventilation?
respiratory rate and tidal volume
most important inputs to medullary inspiratory neurons at rest come from where?
come from periphereal chemoreceptors and central chemoreceptors
peripheral chemoreceptors
consist of carotid bodies and aortic bodies. their afferent fibers give excitatory input to the medullary inspiratory neurons

These receptors are primarily stimulated by decreases in arterial O2 pressure and increase in arterial H+ conc.
central chemorecptors
in medulla and give excitatory input to medullary inspiratory neurons. They are stimulated by increases in the H+ conc of the brain's extracelluar fluid, largely as a result of changes in blood Co2 Pressure
when does pulmonary ventilation increase significantly?
when arterial Oxygen PRessure fall below 60 mmHg. the low Oxygen pressure increase the rate of firing of the peripheeral chemorectors which stimulates the medullary inspiratory neurons. the increase in ventilation increases the delivery of oxygen to the alveoli and increases the arterial Oxygen
are small reduction of arterial oxygen a major stimuls for increasing ventilation?
Flow chart. what happens when inspired oxygen pressure decreases?
decrease alveolar oxygen pressure

decrease arterial oxygen pressure

increase firing of peripheral chemoreceptors

reflex via medulllary respiratory neurons to increase contractions of resp. m.

increase ventilation

return of alveolare nad arterial oxygen pressure to normal
Does a small icrease in arterial CO2 pressure cause a big increase in ventilation?

differs from O2
what does control of ventilation related to changes in CO2 caused by
H+ conc. Increase H+ conc. increases rate of fining of both central and peripheral chemoreceptors
decrease production of non CO2 acid (H+ w/o CO2)

increase arterial H+

peripheral chemoreceptors fire

reflex via medulalry respiratry neurons cause respiratory m. to increase contraction

increase ventilation

decrease alveolar PCO2

decrease arterial PCO2

Return of aterial H+ to normal
How to distinguish where H+ comes from.
metabolic acidosis does not stimulate central chemorectors bc H+ cant cross blood brain barrrier but Respiratory acidosis does stimulate central rectors bc CO2 can cross blood brain barrier

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