Lectures 1 & 2 Flashcards
What is the Physiological definition of Respiration?
The transport of Oxygen from ambient air to cells in the tissues and the transport of CO2 out of the tissues into ambient air
Why do we need a respiratory system?
Anything bigger than a cubic millimeter needs blood supply due to limited diffusion because of size
What are the 4 Phases of Respiration?
- Ventilation
- Diffusion (Alveoli to Pulmonary Capillaries)
- Transport
- Diffusion (O2 to Tissue and CO2 to blood)
What jobs do the lung do?
- Conduction of air
- Diffusion of gas
- Transport
- Metabolism (in Epithelial cells)
- Defense
What is the Conducting Zone and what parts of the lung are included here?
The Anatomical Dead SpaceParts AKA parts of the lung that conduct inspired air but DO NOT take part in gas exchange (diffusion):
- Trachea (0)
- Bronchi (1-3)
- Bronchioles (4-5)
- Terminal Bronchioles (6-16)
Why is branching of the lungs important?
Branching of the Lungs INCREASES the Cross-Sectional Area of the Airways which DECREASES Pressure Change which DECREASES Flow and FACILITATES Gas Exchange
What is the equation for Change in Pressure (∆P)?
∆P= Force/Area
How does ∆P effect Flow (equation and relationship)?
Flow= Volume/Time
AND
Flow= ∆P/Resistance
So decreased Pressure Change also decreases flow
Where is Flow the fastest?
Trachea and Bronchi (Upper parts of the Conducting Zone) since they have the smallest area
What is the relationship between Cross-Sectional Area and Velocity?
Inversely Proportional
As Cross-Sectional Area goes up, Velocity goes down
What is the definition for the diffusion of gas?
Passive movement of molecules/particles DOWN their concentration gradient
What factors would increase the Rate of Diffusion for a gas across a permeable membrane?
- (A) Increase in Surface Area of the Membrane
- (T) Decrease in Thickness of Membrane
- (∆P) Increase in Partial Pressure gradient across the membrane
- (D) Increase the Diffusion Coefficient of the Gas
What is the formula for the Diffusion Coefficient?
D= Solubility Coefficient/ Square Root(Molecular Weight of the gas)
What is the one exception to the Diffusion Coefficient being greatest for small molecules?
Helium, it is the smallest gas molecule but it diffuses very slowly.
CO2 vs. O2 Diffusion
CO2 is very soluble and diffuses 20x faster than O2
What are the constituents of the Alveolus?
- Type I Pneumocytes (majority of lung Surface Area)
- Type II Pneumocytes (make surfactant)
- Very thin Alveolo-Capillary Membrane (0.3-0.5 micrometers)
What is usually not impacted by a thickened Alveolo-Capillary Membrane, unless you are in a state of very serious disease?
CO2 diffusion because it is so soluble
What are some facts about Pulmonary Circulation?
- Lung is reservoir for blood
- Lung receives almost all CO
- Low Resistance Circuit
- Good Flow (Even though Resistance is low, so is ∆P)
- Alveoli are bathed in blood for efficient gas exchange
Describe Vascular Resistance in Extra-Alveolar Vessels
J-Shaped curve where Vascular Resistance drops then increases greatly when Volume is increased
What is Pulmonary Vascular Resistance?
A U-shaped curve that is the Sum of Resistance in Alveolar Blood Vessels and Resistance in Extra-Alveolar Blood Vessels
What is Functional Residual Capacity?
Resting state or the “Sweet spot” where blood resistance is the lowest
What happens to vessels in the lung during LOW lung volumes?
- INCREASED Extra Alveolar Vessel Resistance
2. DECREASED Alveolar (Capillary) Vessel Resistance
What happens to vessels in the lung during HIGH lung volumes?
- DECREASED Extra Alveolar Vessel Resistance (due to expanding lung pulling vessels apart)
- INCREASED Alveolar (Capillary) Vessel Resistance
What is Recruitment?
- Occurs during exercise
2. Blood vessels that are usually occluded in the resting state become active which increases blood flow
What are some factors that affect Pulmonary Circulation?
- Pressures around the Vessels?
- Recruitment (increased blood flow)
- Hypoxemia (Vasoconstriction in the lung)
- Nitric Oxide (Vasodilation)
- Acid-Base Status (Alkalemia VASODILATES the lung)
Why don’t the Alveoli Collapse at LOW Lung Volume?
Surfactant (an amphipathic molecule) inhibits Surface Tension’s force to collapse the lung at low volume
What cells produce Surfactant, where does it work best, and what does it do?
- Type II Pneumocytes produce Surfactant
- Surfactant works best in the Alveoli when there is LOW LUNG VOLUME because they are closer together
- Reduces Surface Tension
- Contributes to Hysteresis (more pressure to inflate lungs than deflate)
When do babies start to produce Surfactant?
Around 32 weeks
-babies born before 32 weeks have Respiratory Distress Syndrome
What is one cure for Persistent Pulmonary Hypertension in Newborns?
Inhaled Nitric Oxide
Is Pulmonary Circulation a HIGH or LOW Resistance Circuit?
Pulmonary Circulation is a LOW Resistance Circuit
What does Lung Expansion do to Extra-Alveolar Resistance?
Extra-Alveolar Resistance DECREASES as the Lung expands
What are some metabolic processes carried out by the lung?
- Produces ACE which in turn generates Angiotensin II (Vasoconstrictor)
- Metabolizes Bronchoactive substances and Xenobiotices
- Reservoir of CYPs
- Contain Mast cells (make anticoagulants like Heparin)
How does the lung act as a line of defense?
- Produces IgA
2. Cilia on the cells that line the airway provide a moving carpet of mucous to get pathogens out of the lung
What is Boyle’s Law and how does it explain how air moves as we breathe?
- Pressure (P) x Volume (V) = Contant (K)
At constant temperature, the product of a gas’s Pressure and Volume is Constant - As V INCREASES, P DECREASES
Is Inspiration Active or Passive and why?
Inspiration is Active because as you increase Volume you decrease the pressure in the lungs causing air to move down its concentration gradient and into the lungs
Why is Expiration Passive?
Elastic Recoil of the Chest Wall decreases the Volume of the chest therefore increasing Pressure so air flows out passively down the pressure gradient
When is Expiration active?
- Playing a wind instrument
- Asthma
- Exercise
In the lungs, what is the air flow considered?
Transitional which means that it is not quite Laminar but not quite Turbulent
What is the equation for Resistance?
R=η8L/πr^4
How would the Resistance of an airway be affected if the radius was cut in half?
Since the equation is (R=η8L/πr^4), cutting the airway in half would increase Resistance by 16
How can airway inflammation be treated?
Administering Heliox: 80% He and 20% O2 which converts Turbulent Flow to Laminar Flow by decreasing Fluid Density (decreases Reynold’s Number)
Where does the most airway resistance occur?
Around the 7th Generation
What is the relationship between Lung Volume and Airway Resistance (AWR)?
Greater the Lung Volume the Lower the Airway Resistance
What happens at the Choke Point?
Flow Volume is INDEPENDENT of Effort
What determines flow at Dynamic Compression?
The gradient between Alveolar Pressure and Pleural Membrane Pressure as the airway is compressed
What is the Choke Point
Point where pressure difference between Alveoli and Pleural Membrane causes airways to collapse making the movement of air INDEPENDENT of effort
What is Lung Compliance, what is the formula for Compliance, and what is an example of something that is compliant?
- How much the Volume changes for a given Pressure
- Compliance = ∆V/∆P
- Party balloon is Compliant
- Hot Water Bottle is NOT Compliant
Does the Lung require more pressure to inflate or deflate?
Lung requires more pressure to INFLATE
Does a person with Emphysema or Asthma have more or less Compliant lungs?
MORE Compliant, meaning less Pressure is required to change Lung Volume
Does a person with Fibrosis or Smoker’s Lung have more or less Compliant lungs?
LESS Compliant, requires much greater Pressure to change the Lung Volume because lungs are stiffer
Does an older person have more or less Compliant lungs and why?
MORE Compliant, because degraded tissue has reduced the recoil of lungs
What are some factors that Increase Compliance (less Pressure)?
- Aging
2. Emphysema
What are some factors that Decrease Compliance (More Pressure)?
- Pulmonary Fibrosis
- Alveolar Edema (fluid in lungs)
- Hypoventilated Lung
- High Pulmonary Venous Pressure
What is Pneumothorax and how is it treated?
- Loss of Negative Pressure in the Pleural Space causing it to go from a potential space to an actual space (i.e. stab wound
- Chest tube sucking air out to reinflate the space
What is Functional Residual Capacity?
- Volume of the lung where elastic recoil pulling it inwards is equal to the tendency for the chest wall to spring out
- This Volume in the lung KEEPS THE LUNG OPEN and acts as O2 reservoir
What would adding Saline to the lungs prove?
- That Surfactant contributes to Hysteresis (more pressure required to inflate lung than deflate)
- Adding Saline makes the inflation and deflation pressure the same
What is the difference between Type I and Type II Pneumocytes?
- Type I non replicating and involved in gas exchange
2. Type II secrete surfactant and can differentiate into Type I
The Apex of the lung has…
Think of holding wet dish sponge up in the air between two fingers:
- High Volume
- Low Pressure
- Not much room for expansion
The Base of the lung has…
Think of holding wet dish sponge up in the air between two fingers:
- Low Volume
- High Pressure
Is Ventilation (change in Volume with inspiration) greatest in the Apex or the Base of the Lung?
Base
At very low lung volumes what happens to Recoil and Ventilation?
- Recoil is reduced at the Base of the Lung
2. Ventilation is better at the Apex (only situation)
