Pulmonary Flashcards
Describe the processes of ventilation.
ventilation = breathing
it is a mechanical process that moves air into and out of the lungs
Take a breath and describe the path that the inhaled gases took to reach the alveoli.
nasal cavity
pharynx
nasopharynx = passageway for air
upper part of throat
oropharynx = passageway for food, water, and air
communicates w/ trachea and esophagus
epiglottis covers trachea during swallowing
hypopharynx → connects larynx to esophagus
larynx (through glottis and vocal cords)
the larynx directs air to the trachea
closes to protect trachea during swallowing
trachea
R & L primary bronchi
secondary bronchi
tertiary bronchi (more branching)
terminal bronchioles
respiratory zone (respiratory bronchioles)
terminal alveolar sacs
Describe the anatomy of the capillaries and alveoli in the lungs. How does this anatomy facilitate gas exchange?
- alveoli = air sacs in the lungs where gas exchange occurs
- connected to each other by connective tissue
- ducts/pores allow alveoli to communicate with each other
- when one alveolus contracts/expands, it brings about contraction/expansion of its neighboring alveoli
- grape clusters do not accurately represent alveoli because you can’t “pluck” one alveolus away from the others
- large surface area increases the rate of gas diffusion
- the membrane of each alveolus is one cell layer thick, plus a basement membrane
- capillary beds surround the alveoli
- there is very little tissue between the alveoli and the lumen of the capillaries
- important bc more tissue/greater distance between them = slower diffusion of gases
Describe pulmonary edema and processes that might contribute to it.
- pulmonary edema - vasculature of the lungs becomes very porous and fluid moves out of the bloodstream in large quantities and fills up the alveoli
- feels like you’re “breathing through water”
- processes that might contribute to it (see lecture 1 slide 22) (Do not need to memorize this slide)
- injury to alveolar-capillary membrane → triggers an inflammatory response
- – increase in cell membrane permeability
- – increased movement of fluids out of the vasculature
- – the only place it has to go is into the alveoli
What structures are found in the mediastinum?
heart
trachea
great vessels
Describe the anatomy of the double layered membrane that surrounds each lung and the relationship of that anatomy to respiration.
parietal pleura - lines the cavity and is attached to the thoracic wall, the mediastinum, and the diaphragm
visceral pleura - covers and adheres to the lungs
pleural space - fluid filled space between the parietal and visceral pleura
Does any part of this double layered membrane attach to the thoracic wall. If so, why?
Yes, the parietal pleura attaches to the thoracic wall
The thoracic cage expands when we inhale and the parietal pleura is pulled while the visceral pleura stays stationary
What is the function of parietal and visceral pleura membrane?
this membrane allows the volume of the pleural cavity to expand, thus making respiration possible
Why is it essential = double layered membrane
Enables the thoracic cavity to expand/contract volume as a unit -> if not airtight the pressure gradient driving alveoli gaining O2
What role does the diaphragm play in ventilation?
expands and contracts the thoracic cavity
“fatigue resistant”
ambient pressure
ambient pressure - pressure of air outside the body (760mmHg, fairly constant)
Please tell the class about the events of inspiration.
- thoracic cavity expands
- diaphragm contracts and moves inferiorly toward the abdominal cavity
- external intercostals move ribs upward and outward → rib cage expands → volume of thoracic cavity increases
- increased volume of pleural cavity
- the adhesive force of the pleural fluid forces the lungs to stretch and expand as the thoracic cavity expands
- decreased inta-pleural pressure
- increased transpulmonary pressure gradient
- expansion of alveoli and a further decrease in intra-alveolar pressure (falls further below atmospheric pressure)
- ambient air flows down the pressure gradientthese steps are reversed during exhalation
What is needed to drive the gas exchange between the blood and the alveoli?
the change in partial pressure from the alveoli to the capillaries drives oxygen into tissues and CO2 into the blood
Tidal volume
- tidal volume (TV) - amount of air expired or inspired in quiet breathing
How does the tidal volume change as one increases aerobic exercise intensity to near max?
When we maximally exercise, respiration rates go up and the depths of respiration go up
Tidal volume and breathing frequency will increase
Explain the concept of compliance. How does a decrease in compliance impact ventilation? How does an increase in compliance impact ventilation?
lung compliance = lung stretchability or elasticity
defined as the change in lung volume per change in transpulmonary pressure
ease with which the lungs expand under changes in pressure
greater compliance = greater change in volume per change in pressure
easier for the lungs to expand, lower work, and energy cost type
lower compliance = more difficult for lungs to expand
muscles have to work harder to contract and expand the chest and alveoli
compliance is reduced by factors such as:
fibrosis (scarring) which reduces elasticity
reduced surface tension of the water layer on the alveolar surfaces
decreased compliance = increased stiffness
Explain surface tension to the class. Why do we care about surface tension under normal situations, under pathological situations?
- surface tension is created by the fluid secreted onto the lining of the alveoli
caused by attractive forces between fluid molecules - this fluid aids in diffusion of gases, but acts to cause the alveolus to favor collapsing and offers resistance to lung expansion/distension
- surfactants are secreted by type 2 alveolar cells and they move into the water layer (alveolar fluid) to reduce surface tension. Meaning that it costs less to inhale
Calculate the partial pressure of O2 in the alveoli assuming a total gas pressure of 760 mmHg and a fraction of O2 of 21%. What law is this question referring to.
Dalton’s Law: atmospheric pressure represents the sum of the partial pressures of the gases in the atmosphere
PO2: 760 mmHg x 21%= 159.6 mmHg
Explain how the uncorking of a bottle of Champagne is similar to the movement of gases in the alveoli.
when you uncork a bottle it fizzes because CO2 moves out of the solution and into the space above
Henry’s Law when liquid is exposed to air containing a particular gas, molecules of that gas will dissolve in the liquid
Explain in excruciating detail this figure.
- shows the linkage between the 3 cog system
- air enters the alveoli, the PO2 is greater than PCO2 in the alveoli and as they are - leaving the alveoli, they go to left heart through the pulmonary veins, out to the body, no change in pressure until it gets to the tissue capillaries, O2 moves into the working cells (mito) and CO2 enters the blood, they go to right heart through the pulmonary arteries.
Why is measuring the oxygen in the venous blood not very useful clinically?
Only tells hemoglobin saturation not how much O2 is dissolved in the blood itself
What actually determines the pressure of O2 in the circulation?
the amount of dissolved O2 in the blood (arterial oxygen, PaO2) has the determining role in moving O2 on and off of the hemoglobin
PaO2, no matter how small, determines the partial pressure of O2
increasing PaO2 → increased PaO2 pressure gradient between arterial blood and tissues
What does Henry’s law have to do with gas exchange in the body?
- the amount of gas dissolved in a solution is directly proportional to the pressure of the gas above the solution
- Partial pressure of O2 is greater in the alveoli than in the venous blood so this difference drives oxygen from the alveoli into the capillary blood and RBC
Describe the anatomy that makes it possible for pulmonary circulation to be a low pressure system.
- blood in the pulmonary circulation travels a shorter distance than the systemic, the pulmonary arteries have larger diameters than the systemic, pulmonary arteries/veins are short, pulmonary vessels are thin and distensible thus compliant.
- the compliance of the vessels in pulmonary circulation is much higher so that means they offer less resistance to flow so the RV does not have to pump against the same challenges that the LV does and that allows the RV to generate and successfully deliver blood at a much lower pressure
- benefit to low circulation is that it reduces the likelihood of pulmonary edema occurring
intrapleural pressure
intrapleural pressure - pressure within the pleural cavity
transpulmonary pressure
transpulmonary pressure - difference between alveolar pressure and pleural pressure
intra-alveolar/intrapulmonary pressure
intra-alveolar/intrapulmonary pressure - pressure within the alveoli
- differences between ambient air pressure and alveolar air pressure are created by changes in volumes of the thoracic and pleural cavities
inspiratory reserve volume
inspiratory reserve volume - amount of air that can be forced in or inhaled after a tidal volume
expiratory reserve volume
expiratory reserve volume - amount of air that can be forced out or exhaled after a tidal volume
forced vital capacity (FVC)
forced vital capacity (FVC) - max amount of air that can be forcefully exhaled after a max inhalation
FVC1 = volume of air that can be exhaled in 1 second
decreased in COPD, emphysema
residual volume (RV)
residual volume (RV) - volume of air remaining in the lungs after maximum forceful expiration
functional residual capacity
functional residual capacity - volume of air present in the lungs at the end of passive expiration
total lung capacity (TLC)
total lung capacity (TLC) - amount of gas in the lungs after max inspiration
TLC = VC + RV
TLC = IRV + TV
IRV = inspiratory reserve volume
what drives movements of air
Pressure differentials
Pulmonary reserves do what with age
decline
