Respiratory Physiology (Part 1) Flashcards
What is the function of the respiratory system?
To exchange oxygen and carbon dioxide between the environment and the cells of the body
The structures of the respiratory system are subdivided into 2 zones, what are they?
- The conducting zone
- The respiratory zone
What structures are included in the conducting zone?
- nose
- nasopharynx
- larynx
- trachea
- bronchi
- bronchioles
- terminal bronchioles
What are the funcitons of the conducting zone?
Bring air into and out of the respiratory zone for gas exchange and to warm, humidify, and filter the air before it reaches the critical gas exchange region
What is the main conducting airway?
the trachea
The trachea divides into how many different divisions?
23
What lines the conducting airways and what are their function?
Mucus-secreting and ciliated cells that function to remove inhaled particles
Do the walls of the conducting airways contain smooth muscle?
yes
Describe sympathetic innervation of smooth muscle in the conducting airways
Sympathetic adrenergic neurons activate beta2 receptors which leads to relaxation and dilation of the airways
Describe parasympathetic innervation of smooth muscle in the conducting airways
Parasympathetic cholinergic neurons activate muscarinic receptors, which leads to contraction and constriction of the airways
How are beta2-adrenergic agonists help treat asthma?
They are used to dilate the airways
The alveoli lined structures of the respiratory zone participate in what?
gas exchange
What structures are included in the respiratory zone?
- respiratory bronchioles
- alveolar ducts
- alveolar sacs
Why are the respiratory bronchioles considered transitional structures?
They have cilia and smooth muscle like the conducting airways, but are also considered part of the gas exchange region because alveoli occasionally bud off their walls
What lines the alveolar ducts and alveolar sacs?
alveloi
What are alveoli?
Pouchlike envaginations found in the walls of the respiratory zone in which gas exchange occurs
Why can the exchange of oxygen and carbon dioxide between alveolar gas and pulmonary capillary blood occur rapidly and efficiently?
Because the alveolar walls are thin and have a large surface area for diffusion
What are the epithelial cells that line the alveolar walls called?
type I and II pneumocytes
What do the type II pneumocytes synthesize?
Pulmonary surfactant which have regenerative capacity for the type I and II pneumocytes
What are the phagocytic cells in the alveoli called?
alveolar macrophages
Why is pulmonary blood flow not distributed evenly in the lungs?
Because of gravitational effects
When a person is standing, blood flow is ____ at the apex and _____ at the base of the lungs
lowest
highest
What happens to the gravitational effects when a person is supine?
They disappear
How is the regulation of pulmonary blood flow accomplished?
by altering the resistance of the pulmonary arterioles
What controls changes in pulmonary arteriolar resistance?
local factors, mainly oxygen
What is bronchial circulation?
The blood supply to the conducting airways (which do not participate in gas exchange) and is a very small fraction of the total pulmonary blood flow
Static volumes of the lungs are measured with what?
a spirometer
What does normal tidal volume equal?
500 mL
What does normal tidal volume include?
The volume of air that fills the alveoli plus the volume of air that fills the airways
What is inspiratory reserve volume?
The additional volume that can be inspired above tidal volume
What does inspiratory reserve volume equal?
3000 mL
What is expiratory reserve volume?
The additional volume that can be inspired below tidal volume
What does expiratory reserve volume equal?
1200 mL
What is residual volume?
The volume of gas remaining in the lungs after a maximal forced expiration
What does residual volume equal?
1200 mL
Describe inspiratory capacity (IC)
It is the lung capacity composed of the tidal volume plus the inspiratory reserve volume
What does inspiratory capacity normally equal?
3500 mL (500 +3000)
Describe functional residual capacity (FRC)
It is the lung capacity composed of the expiratory reserve volume plus the residual volume
What does functional residual capacity normally equal?
2400 mL (1200 + 1200)
Functional residual capacity can be thought of as what? Explain why
The equilibrium volume of the lungs, because it is the volume remaining in the lungs after a normal tidal volume is expired
Describe vital capacity (VC)
It is the lung capacity composed of the inspiratory capacity plus the expiratory reserve volume
What does vital capacity normally equal?
4700 mL (3500 + 1200)
Vital capacity is the volume that can be expired after maximal ______.
inspiration
What does total lung capacity include? What does it equal?
All of the lung values
Vital capacity (4700) + residual volume (1200) = 5900 mL
What is dead space in the lungs considered?
The volume of the airways and lungs that does not participate in gas exchange.
What are the 2 types of dead space?
- anatomic
- physiologic
What is anatomic dead space?
The volume of the conducting airways
What does the volume of the conducting airways or anatomic dead space equal?
1/3 of each tidal volume, which is approximately 150 mL
What is physiologic dead space?
The total volume of the lungs that does not participate in gas exchange
What does physiologic dead space include?
Anatomic dead space of the conducting airways plus functional dead space in the alveoli
Physiologic dead space can be thought of as what?
Ventilated alveoli that do not participate in gas exchange
What is the most important reason that alveoli do not participate in gas exchange?
There is a mismatch of ventilation and perfusion, in which ventilated alveoli are not perfused by pulmonary capillary blood
Ventilation/perfusion defect
What does a ventilation/perfusion defect indicate?
Physiologic dead space is larger than anatomic dead space
What does physiologic dead space equal?
Tidal volume (500 mL) multiplied by a fraction the represents the dilution of alveolar CO2 partial pressure by dead space air
What is ventilation rate?
The volume of air moved into and out of the lungs per unit time
What is minute ventilation?
The total rate of air movement into and out of the lungs
How do you calculate minute ventilation?
multiple tidal volume by the number of breaths per minute
What is the difference between minute and alveolar ventilation?
Alveolar ventilation corrects for the physiologic dead space
How do you calculate alveolar ventilation?
Multiple tidal volume minus physiologic dead space by the number of breaths per minute
What is the alveolar ventilation equation?
An equation that describes the inverse relationship between alveolar ventilation and alveolar CO2 partial pressure
State the alveolar ventilation equation
Alveolar ventilation = (CO2 production rate x 863) / alveolar CO2 partial pressure
What determines alveolar CO2 partial pressure if CO2 production is constant?
alveolar ventilation
Increases in alveolar ventilation cause _____ in alveolar CO2 partial pressure
increases
and vice versa, decreases cause decreases
When CO2 production doubles from 200 mL/min to 400 mL/min, what happens to alveolar ventilation and why?
It must double to maintain the alveolar CO2 partial pressure at 40 mmHg
What is forced vital capacity?
The total volume of air that can be forcibly expired after a maximal inspiration
Describe the concept of FEV1, FEV2, and FEV3
- FEV1 is the volume of air that can be forcibly expired in the first second
- FEV2 is the cumulative amount of air that can be forcibly expired in 2 seconds
- `FEV3 is the cumulative amount of air that can be forcibly expired in 3 seconds
Why is there no FEV4?
Because the entire vital capacity can be forcibly expired in 3 seconds
What 2 lung volumes can useful indices of lung disease?
FVC and FEV1, specifically the fraction of the vital capacity that can be expired in the 1st second
Describe how FVC and FEV1 are affected in a patient with asthma
They are both decreased, however FEV1 is decreased more than FVC is
Describe how FVC and FEV1 are affected in a patient with fibrosis
They are both decreased, however FEV1 is decreased less than FVC is
The FEV1/FVC ratio ______ in asthma patients and ______ in fibrosis patients
decreases
increases
What is normal FEV1/FVC ratio? Why does this indicate?
0.8, meaning 80% of the vital capacity can be expired in the first second of forced expiration
