Respiratory Physiology I Flashcards
*Describe the following components of respiration: the conducting zone, the respiratory zone, alveoli, blood vessels, elastic connective tissue, pleural sac
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*Describe the anatomic function that makes the lung ideally suited for gas exchange
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*Describe the relevant pressures for airflow. Identify the forces that generate the negative intrapleural pressure and the implications of air introduced into pleural activity.
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What is the main function of lungs?
GAS EXCHANGE
What are the 4 processes required for optimal gas exchange?
- Ventilation- getting gas to alveoli
- Perfusion- removing gas from the alveoli by the blood
- Diffusion- getting gas across alveolar walls
- Control of breathing- regulating gas exchange
What are the components of airways and how do they change as they go further into lungs?
Airways consist a series of branching tubes that become NARROWER, SHORTER and more NUMEROUS as they penetrate deeper into the lung
Compare and contrasts the conducting zone, respiratory zone.
Conducting zone- contain Trachea, bronchi and terminal bronchioles(0-16); NO Alveoli, NO Gas exchange occurs
Respiratory Zone- contain respiratory bronchioles(transitionary; small amount of alveoli) , alveolar ducts and Alveolar sacs(17-23); contain Alveoli
What part of airways represent anatomical dead space?
Conducting zone (since they have no alveoli, no gas exchange
How many alveoli are present in alveoli, how much of this comprises of surface area?
300 million alveoli in lungs, creating total surface area of 75 m^2
Describe what alveoli are, compared to an alveolus.
Alveoli are small, thin-walled inflatable sacs encircled by pulmonary capillaries
Alveolus- single layer of thin exchange epithelium that is site of Gas exchange.
What is the role of Pores of Kohn?
Pores of Kohn is what allows air to flow between adjacent alveoli
pore of Kohn also allow air pressure throughout lung to to be equalized
Where in the airways is velocity of air flow highest?
Velocity of air flow is highest in trachea (conducting zone) and Lowest in terminal bronchioles
What are the three main types of cells in alveoli?
- Type I alveolar cells: Very thin, allowing Gas exchange
- Type II alveolar cells; Thicker, secrete surfactant to ease lung expansion
- Alveolar macrophage- protect and defend
What is the importance of intrapleural fluid?
Intrapleural sac in lung secretes small fluid that has great cohesiveness to hold opposing pleural layer together and create slippery surface, allow movement of membranes as lungs move.
Describe the different pressures involved in air flow movement
- Atmospheric pressure (P B)=760 mmHg at sea level; Decreases as altitude increases
- Intra-alveolar pressure (P A)- total gas pressure in alveoli of lungs; *will equillibriate with atmospheric pressure
- Intrapleural pressure- (Pip)= 756 mmHg; recoil forces create a vaccum (4); closed cavity
- Transmural pressure (P L)- pressure across the lungs (PA - Pip); Key to INFLATING Lungs.
What are the important factors that hold lungs and thoracic wall together in tight place?
The Intrapleural fluid’s COHESIVENESS and TRANSMURAL pressure (most importantly) hold the lungs and thoracic wall in Tight apposition, even though the lungs are smaller.
Which pressure has a slightly negative pressure and why?
Intrapleural pressure or PLEURAL SPACE has a slightly negative pressure because the chest is pulling out, lungs are pulling in and there is no extra fluid to fill expanded space .
What is Pneumothorax?
Pneumothorax: Air enters pleural cavity, interpleural pressure equalizes with atmospheric pressure, transmural pressure gradient is gone, lungs collapse and thoracic wall springs out.
*Explain how pleural pressure, alveolar pressure, airflow and lung volume change during normal quiet breathing cycle. Describe how differences in pressure between the atmosphere and alveoli can cause air to move in and out of lungs
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*Identify the muscles utilized for breathing and whether the process is active or passive
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*Describe the importance of airway radius on resistance. List the factors that control cross-sectional area
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*Explain the effect of a reduction in elastic recoil pressure (emphysema) on the location of the equal pressure point
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*Draw the normal lung volume spirogram, labeling the four lung volumes and four capacities. List the volumes that make up each of the four capacities. Identify which volume and capacities is higher or lower than normal.
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*Define surface tension and discuss the role of surfactants.
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What is Boyle’s Law? What is the relationship[ between the two variables?
Boyle’s Law- Describes the relationship between the pressure and volume of a gas (P1xV1=P2xV2). As Volume decreases, pressure increases (vice versa)
Explain the changes in volume of chest cavity and how that can affect pressure.
Changes in volume of chest cavity during ventilation cause PRESSURE GRADIENTS. An INCREASE in chest volume causes decrease in pressure, air moves IN from atmosphere
A decrease in chest volume ,causes increase in pressure, air moves OUT from the body
What occurs during inspiration? What kind of process is this?
Inspiration- contraction of diaphragm and intercostal muscles (ACTIVE process). The rib cage swings Upward and Outward. The enlarged cavity, housing lungs undergoes pressure REDUCTION (with respect to pressure outside body)
What occurs during expiration? What kind of process is this?
Expiration: Relaxation of diaphragm and intercostal muscles (PASSIVE) process. The rib cage moves Inward and downwards. The ELASTIC recoil of lungs creates HIGHER intralveolar pressure compared to atmospheric pressure, forcing air out lungs
What are the two different types of airflow and how can they be distinguished?
Airflow can be LAMINAR ,(LOW flow rate; usually in SMALL airways) or TURBULENT (Fast flow rate usually in LARGE airways).
Describe the resistance, cross-sectional area and resistance for terminal bronchioles.
although, Each terminal bronchiole has a HIGH resistance to flow, their total-cross sectional area is LARGE and the tubes are in PARALLEL, so overall contribution to total resistance R is less low.
How does airflow in respiratory system compare to blood flow?
Air flow in the respiratory system obeys the same rules as blood flow; Air flow= change in P/R.
Flow increases as pressure gradient increases and flow decreases as Resistance increases.
When is Airway resistance greatest and how can it be calculated?
Airway resistance is greatest in MEDIUM sized airways and can be measured using Poiseuille’s Law: R= 8nl/pir^4
r= radius, n= viscosity, l= length
What is the primary determinant of resistance? How does this compare to length and viscosity?
Airway RADIUS is the primary determinant of resistance.
Length and viscociy are CONSTANT in respiratory system, (as in CV system)
Describe the diameter of the bronchiole. Also discuss the effect of Co2 on bronchioles and how it affects resistance, airflow.
The diameter of the bronchiole is Adjustable (no cartilage, but has smooth muscle).
- Low Co2 leads to BronchoCONSTRICTION which increases resistance and DECREASES Airflow
- High Co2 leads to bronchoDILATION and INCREASED Airflow (less resistance)
What is the equal pressure point?
The equal pressure point- when the airway pressure is equal to intrapleural pressure
What is the use of Pulmonary Function Tests? How are they beneficial?
Pulmonary Function Tests- measure the lung volumes, lung capacities and flow rates. These tests can detect ABNORMALITIES in Lung function before diseases become symptomatic.
Describe the four lung volumes that describes the air that moves during breathing?
Four lung volumes:
- Tidal Volume (VT): Air volume moving in a single normal inspiration or expiration
- Inspiratory Reserve Volume (IRV): Additional Volume inspired ABOVE Tidal volume
- Expiratory Reserve Volume (ERV): Air Exhaled BEYOND the end of normal expiration
- Residual Volume (RV): Air in respiratory system after MAXIMAL Exhalation
Describe what lung capacity is and list all the main ones.
Lung capacities- sums of 2 or more lung volumes.
four lung capacities;
1. IRV + ERV+ VT= Vital capacity (VC); MAXIMUM volume of air voluntarily moved through respiratory systems.
2. VC + RV= Total Lung Capacity (TLC)
3. VT + IRV= Inspiratory Capacity
4. ERV + RV: Functional Residual Capacity
Discuss what occurs in obstructive lung disease and provide an example.
Obstructive lung disease (obstruct air flow)- characterized by Increases in Lung volumes and airway resistance, DECREASE in Expiratory FLow rates (FEV1/FVC)
Emphysema- is a specific type of COPD (coronary obstructive pulm. disorder) that has INCREASED lung COMPLIANCE and decreased diffusion capacity for Carbon Monoxide.
Asthma- another obstructive lung disease
Discuss what occurs in restrictive lung disease.
Restrictive lung disease- characterized by Decreases in Lung Volume, Normal expiratory flow rates and resistance, and DECREASE in Lung compliance
restrictive- also due to resistance in expansion of lungs
What diseases are examples of obstructive lung disorders vs restrictive?
Obstructive lung disorders: Emphysema, Asthma
Restrictive lung disorders: fibrosis
Define the term compliance and how a slope curve is used to describe it. What indicates a steep vs flat curve?
Compliance- ability of lungs to STRETCH. It is defined by the slope of pressure-volume curve for lungs: When curve is STEEP at low and Normal lung volumes. Curve FLATTENS at very HIGH Lung volumes.
Differentiate between what happens to lungs in high vs low compliance. Why is there a different compliance for expiration and inspiration?
High compliance lungs- lungs are EASILY stretched
Low compliance lungs- require MORE FORCE to stretch lungs (more work).
Different compliance for expiration and inspiration because of surfactant, Hysteresis (surfactant can change surface tension more rapidly upon expiration)
Explain what the usual cause of decreased compliance vs increase compliance is and what factors may cause it or lead to.
Decreased compliance- usually due to increase in amount of FIBROUS tissue in lung. reduced compliance can also be due to PULMONARY EDEMA (decreases ability to inflate alveoli)- cause breathing difficulties ass. with heart failures
Increased compliance occurs in EMPHYSEMA or Aged lung, due to decrease in amount of elastic tissue.
What is elasticity (elastance)? how does this relate to a normal lung?
Elasticity (elastance) or elastic recoil means the lung is able to Return to its original shape after the force stretching lung has been removed
The normal lung is COMPLIANT and ELASTIC
What are the various differences in an upright lung, and why does this occur?
In upright lung, there are Ventilation differences due to effects of GRAVITY. Gravity causes weight of lung to pull down on alveoli. Alveoli at the Apex are LARGER and LESS Compliant, and receive less of each tidal volume breath than alveoli at the base
Greater compliance at base of lung.
Describe what occurs in the emphysema and how compliance and elastin are affected.
Emphysema- condition in which elastin fibers are destroyed. These lungs have HIGH Compliance and LOW ELASTANCE. They exhibit poor recoil during expiration.
With the changes of emphysema, lung becomes even more compliant, but Less Elastic, resulting in HYPER-Inflated lung and the “Barrel-chest” associated with chronic emphysema.
Explain the possible causes of restrictive lung diseases and how compliance impacted.
Restrictive lung diseases- show REDUCED compliance. More work must be expended to stretch a stiff lung. decreased elastance.
Possible causes- Inelastic scar tissue, Insufficient surfactant production.
what are the two components that generate Pulmonary elasticity?
Pulmonary Elasticity generated by:
1) Elastic Fibers: the natural tendency of these fibers to RECOIL facilitates passive expiration
2) Surface Tension- Surface tension on alveolar surface arises due to strong attractive force that water has for itself. Surface tension tends to make alveoli collapse, particularly in Small alveoli.
What is the role of surfactant?
Surfactant molecules REDUCE Surface Tension
At what point is the chest wall and lung at equilibrium?
The chest wall and lung are in equilibrium at the FRC
FRC- the volume when the elastic recoil of the lung balanced by tendency of Chest wall wanting to Expand
