Structure of the respiratory system, Lung volumes and capacities Flashcards
What are the conducting airways of the respiratory system?
- trachea
- bronchi
- bronchioles
- terminal bronchioles
What are the functions of the conducting system of the lungs?
- Bring air in/out
- Warm air
- Humidify air
- filter air
What do the walls of all conducting airways contain?
SMooth muscle
What impact do sympathetic adrenergic neurons have on the conducting system?
They stimulate relaxation and dilation of the airways via B2 receptors
What do parasympathetic cholinergic neurons do to the conducting system?
activate muscarinic receptors which leads to contraction and constriction of airways
What are the components of the respiratory zone of the lungs?
- Respiratory bronchioles
- Alveolar Ducts
- Alveolar Sacs
- Alveoli
The respiratory bronchioles are transitional structures. In what way are they like the conducting zone? In what way are they like the respiratory zone?
They are like the conducting system because they have cilia and smooth muscle.
They are like the respiratory zone because they occasionally have alveoli branching off their walls and participate in gas exchange.
Describe alveolar ducts. What do they terminate into?
They are completely lined with alveoli, have NO cilia and little smooth muscle.
They terminate into alveolar sacs.
Alveolar Sacs are lined with?
Alveoli
Alveolar walls are rimmed with elastic fibers and lined with epithelial cells. What types of epithelial cells will we find here?
Type I and Type II pneumocytes
What is important about Type II pneumocytes?
- They synthesize surfactant
- have regenerative capacity for type I AND II pneumocytes
Where do we find Dust cells?
What do they do?
Dust cells, AKA alveolar macrophages are found in the alveoli.
They keep alveoli free of dust/debris since alveoli have no cilia to perform this function.
Pulmonary arteries travel with? They divide into?
The bronchi.
Divide into increasingly smaller arteries until the pulmonary capillaries.
What impact does gravity have on blood flow in the lungs?
It prevents even distribution of blood in the lungs, when standing the apex of the lung will recieve less blood than the base. Laying supine, we see the effects of gravity dissapear.
How is regulation of pulmonary blood flow accomplished?
Through alteration of the resistance of the pulmonary arterioles
What is inspiratory capacity composed of?
Tidal volume plus inspiratory reserve volume
Functional residual capacity is composed of?
What is it?
FRC = Expiratory reserve volume + Residual volume
The volume remaining in the lungs after a normal tidal volume is expired. (can be considered the equilibrium volume of the lungs)
What is vital capacity? What is it composed of?
The volume that can be expired after maximal inspiration.
VC = Inspiratory capacity + expiratory reserve volume
What are the two methods used to measure FRC?
Helium dilution
Full body plethysmography
What is PaO2?
Partial pressure of O2 in arterial blood
What is PaCO2?
Partial pressure of CO2 in arterial blood
What is PIO2?
Partial pressure of O2 in dry inspired air
What is PICO2?
Partial pressure of CO2 in dry inspired air
What is PAO2?
Partial pressure of O2 in alveolar air
What is dead space?
The volume of the airways that does not participate in gas exchange
hat is the anatomic dead space?
The volume of the conducting airways (usually 150 ml for a 150 lb person)
What is functional dead space? What is the most important cause of this?
Ventilated alveoli that do not participate in gas exchange. Most imp.: is mismatch of ventilation and perfusion (or ventilation/perfusion defect), where ventilated alveoli are not perfused by capillary blood.
What is physiologic dead space? What volume of phsyiologic dead space should you (ideally) see in a healthy person?
This is the sum of the anatomic dead space (conducting zone volume) and the functional dead space (non-perfused alveoli).
In normal persons, the physiologic dead space should be nearly equal to the anatomic dead space.
What is the formula for the ratio of physiologic dead space to tidal volume?
VD/VT= ?
VD/VT = (PaCO2 - PeCO2)/PaCO2
What is minute ventilation? What is the formula for it?
The total rate of air movement into and out of the lungs
Minute ventilation - VTx breaths/min
What is alveolar ventilation? What is the formula?
Minute ventilation corrected for the physiologic dead space
Alveolar Ventilation (VA) = (VT - VD) x breaths/min
If CO2 production is constant, then what is PACO2determined by?
Determined by alreolar ventilation
because CO2 always equilibrates between pulmonary capillary blood and alveolar gas, the arterial PCO2 always equals…
This is important because…
The alveolar PCO2
This allows us to use PaCO2 which can be measured, in calculations
When alveolar ventilation is halved, what happens to PCO2? Why?
PCO2 doubles.
Because less CO2 is being removed from the alveoli
What is forced vital capacity?
FVC - the total volume of air that can be forcibly expired after a maximal inspiration.
What is FEV1?
The amount of air that can be forcibly expired in one second.
(can also be FEV2 or 3, but no 4 is needed since normally full volume can be exhaled in 3 seconds)
What would you expect to see in the ratio of FEV1/FVC for a patient with an obstructive disease such as asthma?
Reduced ratio
What would you expect to see in the ratio of FEV1/FVC for a patient with an restrictive disease such as fibrosis?
Increased ratio, due to more substantial decrease in FVC than the decrease in FEV1
