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Flashcards in Ex. Phys. Respiratory System Deck (48):

main purposes of respiratory system and ventilation

delivery of O2 to blood
removal of CO2 from blood
maintain acid-base balance in blood


respiratory system structure

thoracic cavity


--those contain

contain network of bronchiole branches with several alveolar sacs
sacs contain pulmonary alveoli, which is where gas exchange occurs


thoracic cavity

visceral pleura: membrane that covers lungs
parietal pleura: membrane that lines thoracic wall
pleural cavity: space between visceral and parietal pleura filled with serous fluid
serous fluid: found inside the pleural cavity; helps adhere lungs to thoracic wall



diaphragm: lowers and elevates the bottom wall of the thoracic cavity
external intercostals: elevate ribs
internal intercostals: depress ribs


ventilation of the lungs
-movement of air is dependent on...

dependent on pressure differences between the atmosphere and the spaces inside the lungs
intrapleural pressure
-air pressure within the pleural cavity
intrapulmonary pressure
-air pressure within the alveoli


Boyle's Law

increased volume = decreased pressure
decreased volume = increased pressure


process of ventilation

1. contraction of diaphragm and external intercostals to increase volume of the thoracic cavity
2. intrapleural pressure decreases, which drops intrapulmonary pressure
3. atmospheric air pressure is now HIGHER than intrapleural and pulmonary pressures, which creates a vacuum inside the lungs
4. atmospheric air is sucked inside, inflating the lungs and supplying O2



1. elastic nature of lungs and thoracic cavity, relaxation of diaphragm, and possible contraction of internal intercostals (and abdominals during exercise) decrease volume of the thoracic cavity
2. intrapleural and intrapulmonary pressures increase…
3. atmospheric pressure is now LOWER than intrapleural and pulmonary pressures…
4. air is forced out of lungs – see ya CO2!


air composition
-inspired (ambient/atmospheric) air

N2 = 79
O2 = 20.9
CO2 = 0.03
H2O = the rest (around 0.5)


air composition

N2 = 75
O2 = 15-17
CO2 = 3-6
H2O = the rest (around 6)


total/atmospheric air pressure

760 mmHg


partial pressure inspired air (atmospheric air pressure)

PIO2 = 760 x .209 = 150 mmHg
PICO2 = 760 x .0003 = 0 mmHg


alveolar blood PP

PAO2 = 102
PACO2 = 40


arterial blood PP

PaO2 = 102
PaCO2 = 40


venous blood PP

PvO2 = 40 mmHg
PvCO2 = -46 mmHg


pertinent lung volumes

breathing frequency (f)
tidal volume (VT)
ventilation (VE)
Total Lung Capacity (TLC)
Residual Volume (RV)
Forced Vital Capacity (FVC)
Forced Expiratory Volume 1, 2, 3


breathing frequency
-what is it

number of breaths taken per minute
resting: 8-12 bpm
aerobic: up to 50-60 bpm
resistance: slightly elevated from rest


tidal volume
-what is it

the volume of air inspired/expired each breath
resting: 0.5 L/breath
aerobic: up to 2-4 L/breath
resistance: slightly elevated from rest


-what is it
-VE =

the volume of expired air per minute
VE = VT x f
resting: 6 L/min
aerobic: up to 150-200 L/min
resistance: slightly elevated from rest


Total Lung Capacity
-what is it

the maximun lung volume (not entirely usable)
average: 5-6 L


residual volume
-what is it

amount of air left in the lungs after a maximum exhalation (reserve air supply)
average - 1.0 L


forced vital capacity
-what is it
-FVC =
-greatly affected by

largest volume of air you can possibly expire in a single exhalation
greatly affected by gender, age, height, and restrictive pulmonary diseases


FEV 1, 2, 3
-what is it
-greatly affected by

the volume of your FVC that can be expired in 1, 2, or 3 seconds
FEV is greatly affected by gender, age, height, and obstructive pulmonary diseases


success of gas exchange is dependent upon

adequate total ventilation (VE) and alveolar ventilation (VA)


VE vs. VA

VE: it is the volume of air that enters the lungs each minute
VA: volume of air that enters the actual alveoli each minute


what accounts for the difference between VA and VE

remember that EV = VT x f
about 150 ml of VT is dead space (DS)
-air in the bronchial pathways that does not participate in gas exchange
VA = (VT - DS) x f
VA is important, then, in terms of pulmonary function


depth of breathing has a large impact on VA

shallow, rapid breathing minimizes VA
slow, deep breathing maximizes VA
aerobic exercise is a balance between the rate and depth of breathing to obtain an adequate VA


gas exchange and transport

integrated processes that sustain metabolism


what processes are included in gas exchange and transport

-loading O2 into the blood on hemoglobin from the alveoli
-removing CO2 from the blood to the alveoli
-transporting O2 to the tissues and unloading in onto myoglobin
-loading CO2 from the tissues into the blood and transporting it to the alveoli


roles of hemoglobin (Hb)

Hb is the iron-containing O2 transport protein found in all RBCs
-initially accepts O2 during gas exchange at the lungs
-also can transport CO2 from the tissues to the lungs for gas exchange
-each Hb molecule can bind up to 4 O2 molecules
--with each O2 that binds, Hb's affinity for O2 increases


roles of myoglobin

iron-containing O2 transport protein found in all muscle tissue
-accepts O2 during gas exchange at the muscles


oxygen transport process

O2 diffuses from alveoli into RBC
-within RBC, O2 binds to Hb
Hb carries 95% of all the O2 that diffuses into blood
remaining 5% of diffused O2 is dissolved in the blood (PO2)
-although small, this is important because it is used to monitor ventilation (primary)
once carried to the muscles, increases 2,3-Bisphosphoglycerate (2,3-BPG), H+, CO2, and temperature induce O2 loading into the muscles
O2 unloaded into muscles onto Mb for use in mitochondrial respiration


Bohr effect

describes how CO2 and H+ affect the affinity of Hb for O2
high CO2 and H+ concentrations decrease affinity for O2, while low concentrations increase affinity for O2


Bohr effect example

in active muscles, CO2 and H+ levels are high
oxygenated blood that flows past is affected by these conditions, and the affinity of Hb for O2 is decrease, allowing O2 to be more easily transferred to the muscles


carbon dioxide transport process

CO2 diffuses from the muscle into RBC
90% of CO2 is converted to H+ and bicarbonate (HCO3-) using the following reaction
-CO2 + H2O --> H+ + HCO3-
-HCO3- binds to Hb for transport to lungs
H+ "buffered" via binding to Hb in the RBC and to specific blood plasma proteins
-this reaction is important because sizeable amounts of CO2 can be transported in the blood to the lungs without substantially altering blood pH
-at lungs, the above reaction is reversed to produce CO2 and H2O, which diffuses into alveoli and is expired


CO2 transport cont.

5% of CO2 is directly bound to and carried by Hb
5% of CO2 is dissolved in blood (PCO2). again, this is very important because it is what is monitored for ventilation regulation


haldane effect

describes how O2 concentrations determine Hb affinity for CO2
-high O2 concentrations enhance the unloading of CO2
-converse is true: low O2 concentrations promote loading of CO2 onto Hb
in both situations, it is O2 that causes change in CO2 levels


haldene effect example

in the lungs, when Hb loaded with CO2 is exposed to high O2 levels, Hb's affinity for CO2 decreases


important factors that affect gas exchange

partial pressure gradients
barriers to diffusion
RBC transit time
Hb and Mb concentrations
Bohr and Haldane effects
ventilation/perfusion ratio


barriers to diffusion

alveolar epithelium
interstitial space
capillary basement membrane
capillary endothelium


RBC transit time

within capillary, transit time is 0.75 sec at rest, down to 0.25 sec with maximal exercise
-at maximal exercise, Hb desaturation occurs, which can make the muscles ischemic


Hb and Mb concentrations

the more Hb that is present in the blood (typically due to increased RBC concentrations), the more O2 that can be carried to the muscles
the more Mb that is present in the muscle, the more O2 than can be accepted into the muscles


ventilation/perfusion ratios
-calculated as
--ideal score
-score variation

calculated as VA/Q
represents the relative efficiency of gas exchange from the alveoli to the blood
-an ideal score is around 1.0
score variation
-lung blood flow varies from the base to the apex, so VA/Q changes depending on region
-really high or really low values typically imply some sort of ventilatory pathophysiology, such as chronic bronchitis, asthma, or COPD


ventilation regulation

ventilatory centers (medulla and pons) in the brain initially adjust ventilation via a feed forward system
sensory receptors through the body adjust ventilation via feedback systems


ventilatory centers
-primary responsibility
-SNS function

primary responsibility for an anticipatory rise in VE
SNS dilates bronchioles to increase airflow into lungs


sensory receptors

mechanoreceptors in muscles often elicit rapid rises and sudden drops in VE due to increases or absence of physical motion
chemoreceptors in the blood vessels are responsible for slow plateaus and gradual declines in VE during sustained exercise or periods of rest


main things monitored by chemoreceptors
-which is primary determinant of ventilation

PCO2, blood pH, LA, epinephrine and norepinephrine, temperature, etc.
-PCO2 is the primary