L21: Respiratory System II Flashcards
airway resistance
refers to the resistance of the entire system of airways in the respiratory tract
when resistance increases, ___
a larger pressure gradient is required to produce air flow
three parameters contributing to resistance
the system’s length, the viscosity, and the radius of tubes
resistance formula
R = (8Ln)/(pi*r^4)
in healthy lungs, resistance to air flow is __
low
why is resistance low in the conducting zone?
radii of tubes are large
why is resistance low in the respiratory zone?
extensive branching
factors affecting viscosity of air
humidity and altitude
factors affecting diameter of upper airways
physical obstruction by mucus or other objects
factors increasing diameter of bronchioles
carbon dioxide, epinephrine
factors decreasing diameter of bronchioles
parasympathetic neurons, histamine, leukotrienes
spirometry
a technique for measuring the volumes of inspired and expired air
how does spirometer work?
an individual breathes into and out of tube and transducer converts the volume of air to electrical signal
what lung volumes can be measured by spirometer?
tidal volume, inspiratory, expiratory reserve volumes
inspiratory reserve volume (IRV)
the maximum volume of air that can be inspired from the end of a normal inspiration
what’s the average IRV?
3000 mL
tidal volume (Vt)
the volume of air that moves into and out of the lungs doing a single, unforced breath
what’s average Vt?
500 mL
residual volume (RV)
the volume of air remaining in lungs following a maximal expiration
expiratory reserve volume (ERV)
the maximum volume of air that can be expired from the end of a normal expiration
what’s the average RV?
1200 mL
what’s the average ERV?
1000 mL
lung capacities
sums of two or more of the lung volumes
inspiratory capacity (IC)
Vt + IRV = 3500 mL
vital capacity (VC)
Vt + IRV + ERV = 4500 mL
functional residual capacity (FRC)
FRC = ERV + RV = 2200 mL
total lung capacity (TLC)
TLC = Vt + ERV + IRV + RV = 5700 mL
minute ventilation is ____ than alveolar ventilation because of ___
greater; dead space
minute ventilation formula
minute ventilation = tidal volume x respiratory rate
dead space
a fraction of fresh air left in upper airways that does not get to the alveoli
what’s the average dead space volume?
150 mL
alveolar ventilation formula
alveolar ventilation = (tidal volume - dead space) x respiratory rate
restrictive pulmonary diseases
involve an interference with lung expansion
obstructive pulmonary diseases
involve increases in airway resistance
restrictive disorders involve
structural damage to lungs, plura or chest
what effect do restrictive disorders have on lung capacities?
decrease of the total lung capacity
what effect do obstructive disorders have on lung capacities?
increase of the functional residual capacity and total lung capacity
why do residual volumes increase in the case of obstructive disorders?
an increase in resistance makes both expiration and inspiration difficult
gas exchange in lungs and tissues involves __
diffusion of O2 and CO2 from regions of higher to lower partial pressure
partial pressure of dry air
760 mm Hg
partial pressure of oxygen in the air
160 mm Hg
partial pressure of carbon dioxide in air
0.25 mm Hg
alveolar partial pressure of oxygen
100 mm Hg
alveolar partial pressure of carbon dioxide
40 mm Hg
oxygen partial pressure in venous blood
40 mm Hg
carbon dioxide partial pressure in venous blood
46 mm Hg
oxygen partial pressure in arterial blood
100 mm Hg
carbon dioxide partial pressure in arterial blood
40 mm Hg
oxygen partial pressure in tissues
less than 40 mm Hg
carbon dioxide partial pressure in tissues
more than 46 mm Hg
each liter of systemic arterial blood contains __ oxygen
200 mL
out of 200 mL, __ are physically dissolved, while ___ bound to hemoglobin
3 mL; 197 mL
hemoglobin
protein made of four subunits bound together
each subunit of hemoglobin consists of ___
heme molecular group and a polypeptide attached to the heme
each of the four heme groups contains ___
one iron atom to which molecular oxygen binds
percent Hb saturation formula
O2 bound to Hb/Maximal capacity of Hb to bind O2
the combination of O2 with Hb is an example of
cooperativity
cooperativity
binding just one oxygen molecule to deoxyhemoglobin increases the affinity of remaining sites of the Hb molecule
shift left
more O2 affinity, more loading, less unloading
shift right
less O2 affinity, less loading, more unloading
increase in DPG causes
shift to the right
increase in temperature causes
shift to the right
increase in acidity causes
shift to the right
increased DPG levels, acidity, temperature are associated with
increased metabolic activity
% Hb saturation at 100 mm Hg P(O2)
98%
% Hb saturation at 60 mm P(O2)
more than 90%
molecules with greater O2 affinity
fetal Hb (exchange of bloods), myoglobin (increased supply of oxygen in muscles)
Hb has a higher affinity for ___ than O2
CO
Hb is __ saturated at venous P(O2) of 40 mm Hg
75%
__% of oxygen dissociates from Hb into the tissues
25%
DPG is synthesized by ___
erythrocytes
DPG increases in situations ___
associated with inadequate oxygen supply and helps maintain oxygen release in the tissues
