Pulmonary Structure & Function Flashcards
Functions of the lungs and the respiratory system
- Gas exchange
- Filter blood - the lungs are a massive capillary bed
-
Metabolize active substances from one form to another
- Angiotensin I –> Angiotensin II
- Bradykinin inactivation
- Prostaglandins, sertonin, and leukotrienes are removed
- Provide a reservoir for blood for the left ventricle
- Generate positive pressure airflow -> phonate
What happens when these things pass through the pulmonary capillary bed?
Blood clots
Bacterial vegetations on the heart valve
Cancers
Blood clots -> pulmonary emboli
Bacterial vegetations -> pulmonary abcesses
Cancers -> metastatic tumors
What is the sequence of layers gasses must pass through to get to hemoglobin?
- Surfactant layer
- Type 1 pneumocytes (epithelial cell)
- Basement membrane of epithelial cell
- Interstitial space between epithelial and ENDOthelial cell
- Basement membrane of endothelial cell
- Endothelial cells of alveolar capillaries
- Plasma of blood
- RBC membrane
- Hemoglobin
What is the function of FB?
What is pulmonary fibrosis?
Fibroblasts: produce collagen to repair damaged tissue when the lungs are injured.
Pulmonary fibrosis: excessive scar tissue from proliferating fibroblasts forms in a lung injury, impairing gas exchange -> hypoxemia
Epithelial vs Endothelial cells
Epithelial cells are in contact with the air outside the body -> vulnerable to inhalational injury & infection
Endothelial cells are in contact with the blood inside the body –> vulnerable to blood-borne substances
The thickness of the barrier between the alveolar air and hemoglobin in RBCs is
0.3
Air moves from high pressure to low pressure.
How do we lower the pressure within the chest below atmoshperic pressure to cause inspiration?
Move the diaphragm down
Move the ribcage out
What has to happen to cause passive exhalation?
Respiratory muscles relax, pushing abdominal contents back up into the thoracic cavity
Elastic recoil of chest wall
What is the purpose of branching of the airways so much from the bronchioles and forward?
Total cross-sectional area increases so much that the forward velocity of the gas slows to a standstill at the alveoli –> gas diffusion takes over
The area of the lungs where gas moves by diffusion and not by bulk flow is …
Respiratory zone
Respiratory bronchioles, alveolar ducts, alveolar sacs
The total volume of the conducting zone (trachea -> terminal bronchioles) is
~150 mL
Anatomic dead space - define it & quantify
The fixed volume of tubing it takes for oxygen to get from the nose/mouth to the alveoli / The conducting zone
~1 mL per pound of ideal body weight –> ~150mL
The maximum volume of the respiratory zone (volume of lungs that contain alveoli) is
Maximum: ~2.5-3L
However, unlike the anatomic dead space, the respiratory zone is highly variable depending on the size of breath!
Volume of an average breath is
0.5L
Minute ventilation
Amt of air that enters and leaves the body per minute
Volume of each breath x Respiratory rate per min
Normal: ~6L/min
Dalton’s law: The sum of all the partial pressures in a gas mixture equals
the atmospheric pressure
=amt of pressure it would take to push up a column of Hg in a tube
= 1 atm
=760mmHg
=14.7ppi (pounsd-per-square-inch)
What’s the proportion of oxygen in the air?
Oxygen = 21%
[FiO2] = .21
(Nitrogen is 78%)
As you go higher in the atmosphere, what happens to pressure?
It decreases.
The proportion of oxygen in the air stays the same, but its pressure decreases.
What is the partial pressure of oxygen in air in mmHg at sea level?
0.21 x 760 mmHg = 160mmHg
Warmer air has more ___ in it than cooler air.
Water vapor
What is the partial pressure of water vapor in the inspired air at body temperature at sea level?
47 mmHg
What is the effective atmospheric pressure of air once it reaches the alveoli, since it gets warmed and humidified in the body?
760 - 47 = 713
(47mmHg is the partial pressure of water vapor in inspired air at body temperature at sea lvl)
What happens to the partial pressure of oxygen as air moves into the trachea? The alveoli?
It decreases because of humidification and addition of CO2.
(760-47) x 0.21 = 150 mmHg after humidification in the trachea
100mmHg after addition of CO2 in the alveoli
Bronchial circulation
small branches off the aorta (so it’s systemic) that supply the conducting airways (bronchi) of the lungs, nerves, and lymph nodes of the lungs
Pressure in bronchial circulation is the same as the ___.
Pulmonary circulation is much ___
bronchial circulation = systemic circulation (~120mmHg)
Pulmonary circulation (~25mmHg) is lower than systemic circulation
What is the purpose of surfactant? What cells produce it? What cells take it up?
Decreases surface tension of the air-liquid interface to prevent alveolar collapse
Produced by type 2 alveolar pneumocytes
Taken up by alveolar macrophages
Atelectasis
Collapsed alveoli
May occur if you lack surfactant
Smaller alveoli are easier to collapse than larger ones
Compliance
How much volume changes in response to changes in pressure
As you decrease surface tension, what happens to compliance?
Decrease surface tension -> increased compliance
Ex) The saline-filled lung has no surface tension –> more compliant than air-filled lung
Hysteresis
The pressure-volume curve changes depending on whether the pressure goes up or down.
How are big particles cleaned out?
Small particles?
Particles that make it all the way down to the alveoli?
Big particles/dust gets mixed with mucus -> boogers that are swallowed or cleared out
Small particles are trapped in the mucus layer lining the airways -> respiratory cilia move them up and out the lungs
Particles that make it to the alveoli are taken up by alveolar macrophages & neutrophils -> lymph nodes for antigen presentation to lymphocytes OR push them up to the conducting zone where cilia transport them up an dout
Which is emphysema?
The leftmost picture.
It has less fibers; tissue destruction; big spaces of air and you can’t get it out.
Chronic bronchitis: productive cough with airway inflammation from long-standing irritation of inhaled substances; can lead to heartfailure, metaplasia, and dysplasia of respiratory epithelium -> cancer
- Increased mucus secretion in large airways due to hypertrophy of submucosal glands + increased goblet cells
- Increased inflammation and fibrosis narrows bronchioles
Which image is chronic bronchitis?
The leftmost picture
It has more mucosal glands & thickened bands of smooth muscle.
Where are the axons in teh submucosa of this olfactory epithelium?
Axons in teh submucosa are a defining characteristic of olfactory epithelium
Nasal cavity should have tall respiratory epithelium, which is bottom right
In the basal lamina!
Which respiratory structure is most involved in an asthma attack? What type of stimulation is involved?
Bronchioles - they have a lot fo smooth muscle and no cartilage. So it’s much mroe responsive to parasympathetic stimulation.
Increased pulmonary resistance and hemosiderin laden macrophages
Blood is getting backed up into pulmonary circulation
Bottom left.
it has no cartilage and the top pic is an alveolar space.
What would you NOT see in an intralveolar septum?
- reticular fiber
- elastic fiber
- pneumocyte type II
- colagen fiber
- fibroblast
- sinusoidal capillary
- basal lamina
- macrophage
There are no sinusoidal capillaries in the lungs.
Which structure assists in adding humidity to inspired air?
Bowman’s glands in the lamina propria secrete mucus.
Is this respiratory or conducting portion?
Conducting
The volume of anatomic dead space is about __mL per pound ideal body weight
1mL per pound ideal body weight
(Obese people’s lungs don’t get any bigger)
Bronchi are defined by the presence of
cartilage, which keeps the airways open
As you go from nose > trachea > alveoli, what happens the partial pressure of O2, H2O, CO2, and N2?
O2 & N2 decrease
H2O & CO2 increase
pO2 =
Patm x FO2
Ex) In Denver, where the barometric pressure is 619mmHg, pO2 = 619 x .21 = 130mmHg
Going from trachea to bronchi, cross sectional area ___
DEcreases
But from bronchi to bronchioles and onwards, it starts increasing
If you haev a high heartrate or the lungs are damaged, then blood will spend ___ time in the pulmonary capillaries.
LESS time in the pulmonary capillaries –> not enough time to equilibrate w/the alveolar gas –> hypoxemia
What is the A-a gradient? Do we want it to be high or low?
The gradient between the alveolus (A) and the pulmonary arteriole (a). (age/4)+4
The lower, the better.
The partial pressure of oxygen
At the nose
At the trachea
At the alveolus
Nose = 160mmHg
Trachea = 150mmHg
Alveolus = 100mmg
Smoking
damages cilia
The pressure inside a distensible sphere (like an alveolus) is determined by
wall tension (directly proportional)
radius of sphere (indirectly)
Usually, small alveoli are higher pressure bc of their small radius, so they would blow up the larger ones and collapse themselves. With surfactant, T is reduced so that P in the smaller alveoli is decreased and equalized w the larger ones.
3 advantages of surfactant
- Lower surface tension & increase compliance –> less work to breathe
- Reduces the tendency of smaller alveoli to collapse and blow up the larger ones
- Reduces hydrostatic pressure in the tissue outside the pulmonary capillaries (keeps the lungs dry)
A premature infant in gestational wk 25 has neonatal respiratory distress syndrome. Which is expected in this infant?
- Arterial pO2 of 100mmHg
- collapse of small alveoli
- Increased lung compliance
- Normal breathing rate
25wk old neonates don’t have surfactant.
So compliance would increase and the small alveoli would collapse.
Increased work to breathe –> shallower breaths
What is the PO2 (in mm Hg) of moist inspired gas of a climber on the summit of Mt. Everest (assume barometric pressure is 247 mm Hg)?
FiO2 x (Barometric pressure-water vapor)
= 0.21 (247-47)
= 42 mm Hg
