Mechanics of Breathing Flashcards
what is respiration?
the exchange of oxygen and co2 w the external environment.
Respiration requires what both systems?
cardiovascular and respiratory systems
the respiratory system consists of those structures that move air into and out of the body. What are the systems called?
upper airways, conducting zone, and respiratory zone
what do the upper airways include?
nose, mouth, pharynx, and larynx
what does the conducting zone include?
trachea, primary bronchi, and bronchi and bronchioles within the lungs
what does the respiratory zone include?
respiratory bronchioles, alveolar ducts, and alveolar sacs (all within the lungs)
how do the systems function?
the upper airways and conducting zone function to transport air to and from the respiratory zone
in which system does gas exchange occur?
within the respiratory zone
gas exchange occurs in tiny, thin-walled sacs called
alveoli
how is the wall of an alveolus structured? what do they consist of?
very thin, consist of a single layer of flat cells called type I cells.
what else also makes up the alveolar wall? besides type I cells.
type II cells are interspersed among the type I cells
what do type II cells produce? what else do they do?
pulmonary surfactant; are also stem cells that produce new type I and II cells
what does pulmonary surfactant do?
prevents collapse of the alveolar wall
what are the outer surfaces of the alveoli covered by?
pulmonary capillaries
what separates the capillary walls from the alveolar walls? what does it consist of?
thin interstitial space; ISF and loose connective tissue
what makes up the respiratory membrane?
alveolar wall, interstitial space, and capillary wall
what occurs across the respiratory membrane? what is the total distance bw the air and plasma?
gas exchange; (very thin) 0.2 micrometers
what is the chest? what is located here?
a closed compartment separated from the neck and abdomen by bone, connective tissue, and muscle; the lungs
each lung is surrounded by what?
a double-walled pleural sac
what is the outer wall of the pleural sac called? what is it attached to?
parietal pleura; attached by connective tissue to the chest and diaphragm muscle
what is the inner wall of the pleural sac called? what is it attached to?
visceral pleura; attached to outer surface of the lung
what are the two pleura layers separated by? what is the hydrostatic pressure of this fluid called?
thin layer of intrapleural fluid; intrapleural pressure
what pressure is important in the process of ventilation?
intrapleural pressure
the exchange of air bw the atmosphere and the alveoli
ventilation
what are the two phases of ventilation?
inspiration and expiration
movement of air from the atmosphere to the alveoli
inspiration
movement of air from the alveoli to the atmosphere
expiration
what does ventilation depend on?
the contraction and relaxation of respiratory muscles
ventilation occurs by what? and what is it?
bulk flow; movement down a pressure gradient higher to lower pressure
because pressures in the chest are set relative to the atmospheric pressure, atmospheric pressure is set at???
0mmHg
what does a negative value for alveolar pressure mean?
that the pressure is lower than atm pressure
what does a positive value for alveolar pressure mean?
the alv pressure is higher than atm pressure
occurs when alveolar pressure is negative
inspiration
occurs when alveolar pressure is positive
expiration
how is airflow calculated?
F= (Palv-Patm)/R
created by changes in the dimensions of the chest wall and lungs
pressure differences
how are alveolar pressure and lung vol related?
inversely related (lung vol increases alv press decreases)
how are pressure changes created?
contraction and relaxation of respiratory muscles
what is the most important respiratory muscle at rest? what does it look like at rest?
diaphragm; dome shape
what happens to the diaphragm when it contracts? what does it do to chest vol and alv press?
flattens the muscle, compressing the abdomen, expands the rib cage up and out; increasing the vol of the chest cavity and lungs, decreasing alveolar pressure.
what happens to the diaphragm when it relaxes? what does it do to chest vol and alv press?
allows the abdomen to expand, compresses the rib cage down and in; decreases the vol of chest cavity and lungs, increases alveolar pressure.
what connects the lungs to the chest wall?
pleural sac
what does the magnitude of vol change depend on?
transpulmonary pressure (Ptp) and lung compliance
the pressure difference bw the alveolar pressure and the intrapleural pressure. what is the formula?
transpulmonary pressure; Ptp= Palv-Pip
transpulmonary pressure is a what kind of pressure? what does that mean?
transmural press; is acts across a barrier (wall of lung and pleural sac)
driving force for expansion or recoil of the lungs? what does an increase in this cause? decrease?
transpulmonary pressure; inc press causes lungs to expand; dec press causes lungs to recoil
measure of the stretchability of the lungs. the higher the more stretch, the higher this value is.
compliance
compliance affects how much ____________ will change with ______________________ changes. what is the formula?
volume; transpulmonary pressure; change in vol= C x change in Ptp
for any given change in transpulmonary pressure, ___________ compliance will cause a _____________ change in vol
higher; greater
which lungs will expand more, the lungs with higher or lower compliance?
higher
what are the two determinants of lung compliance?
stretchability and surface tension
what does stretchability depend on?
amount of elastic connective tissue present
what is surface tension referring to?
the air-water interfaces within the alveoli; surface tension of water resists stretching, making it harder to stretch
how does pulmonary surfactant produced by type II cells affect surface tension?
reduces surface tension, increases compliance, reducing energy needed to expand the lungs
how is airflow affected by resistance?
increases in resistance decreases airflow, decreases in resistance increase airflow
what is the formula for airflow?
F= change in P/R
what is resistance influenced by? what is the formula for it?
length, radius, and viscosity. R=8Ln/pi r^4
what is the most important resistance factor in the lungs? how does it produce change?
radius; small changes in radius produce large effects on resistance
normally, resistance in the airways is low, but it can be affected by what?
chemical signaling
where do chemical signals primarily act on?
smooth muscle in the bronchiole wall
decreases radius and increases resistance
bronchoconstriction
increases radius and decreases resistance
bronchodilation
examples of bronchoconstrictors?
parasympathetic stimulation and paracrine histamine
examples of bronchodilators?
increased sympathetic stimulation and carbon dioxide
