Respiratory - Anatomy and Physiology Flashcards

Question 1

Q

Respiratory tree:
Conducting zone

Structures
Functions
Characteristics

Answer

A

Structures
- Large airways consist of nose, pharynx, larynx, trachea, and bronchi.
- Small airways consist of bronchioles and terminal bronchioles
  - Large numbers in parallel –> least airway resistance
Functions
- Warms, humidifies, and filters air but does not participate in gas exchange –> “anatomic dead space.”
Characteristics
- Cartilage and goblet cells extend to end of bronchi.
- Pseudostratified ciliated columnar cells (beat mucus up and out of lungs) extend to beginning of terminal bronchioles, then transition to cuboidal cells.
- Airway smooth muscles extend to end of terminal bronchioles (sparse beyond this point).

Question 2

Q

Respiratory tree:
Respiratory zone

Structures
Functions
Characteristics

Answer

A

Structures
- Lung parenchyma
- Consists of respiratory bronchioles, alveolar ducts, and alveoli.
Functions
- Participates in gas exchange.
Characteristics
- Mostly cuboidal cells in respiratory bronchioles, then simple squamous cells up to alveoli.
- No cilia.
- Alveolar macrophages clear debris and participate in immune response.

Question 3

Q

Pneumocytes

For each
- Functions
- Characteristics
Type I cells
Type II cells
Club (Clara) cells

Answer

A

Type I cells
- Functions:
  - 97% of alveolar surfaces.
  - Line the alveoli.
- Characteristics:
  - Squamous
  - Thin for optimal gas diffusion.
Type II cells
- Functions:
  - Secrete pulmonary surfactant –> decreased alveolar surface tension and prevention of alveolar collapse (atelectasis).
  - Also serve as precursors to type I cells and other type II cells
  - Proliferate during lung damage
- Characteristics:
  - Cuboidal
  - Clustered.
Club (Clara) cells
- Functions:
  - Secrete component of surfactant
  - Degrade toxins
  - Act as reserve cells
- Characteristics:
  - Nonciliated
  - Low-columnar/cuboidal with secretory granules.

Question 4

Q

Pneumocytes

Collapsing pressure equation
Law of Laplace
Pulmonary surfactant
Surfactant synthesis

Answer

A

Collapsing pressure
- P = [2 * (surface tension)] / radius
Law of Laplace
- Alveoli have increased tendency to collapse on expiration as radius decreases
Pulmonary surfactant
- A complex mix of lecithins, the most important of which is dipalmitoylphosphatidylcholine.
Surfactant synthesis
- Begins around week 26 of gestation
- Mature levels are not achieved until around week 35.
Lecithin-to-sphingomyelin ratio
- > 2.0 in amniotic fluid indicates fetal lung maturity.

Question 5

Q

Lung relations

Right lung
Left lung
The relation of the pulmonary artery to the bronchus at each lung hilus
Where an aspirated peanut travels
- While upright
- While supine

Answer

A

Right lung
- Right lung has 3 lobes
- Right lung is more common site for inhaled foreign body because the right main stem bronchus is wider and more vertical than the left
Left lung
- Left has Less Lobes (2) and Lingula (homologue of right middle lobe).
- Instead of a middle lobe, the left lung has a space occupied by the heart.
The relation of the pulmonary artery to the bronchus at each lung hilus
- Described by RALS—Right Anterior; Left Superior.
Where an aspirated peanut travels
- While upright—lower portion of right inferior lobe.
- While supine—superior portion of right inferior lobe.

Question 6

Q

Diaphragm structures

Structures perforating diaphragm
- At T8
- At T10
- At T12
Diaphragm
- Innervation
- Pain referral

Answer

A

Structures perforating diaphragm
- At T8: IVC
- At T10: esophagus, vagus (CN 10; 2 trunks)
- At T12: aorta (red), thoracic duct (white), azygos vein (blue)
  - “At T-1-2 it’s the red, white, and blue”
- Number of letters = T level:
  - T8: vena cava
  - T10: “oesophagus”
  - T12: aortic hiatus
- I (IVC) ate (8) ten (10) eggs (esophagus) at (aorta) twelve (12).
Diaphragm
- Innervation
  - Innervated by C3, 4, and 5 (phrenic nerve).
  - C3, 4, 5 keeps the diaphragm alive.
- Pain referral
  - Pain from diaphragm irritation (e.g., air or blood in peritoneal cavity) can be referred to the shoulder (C5) and the trapezius ridge (C3, 4).

Question 7

Q

Lung volumes

Inspiratory reserve volume (IRV)
Tidal volume (TV)
Expiratory reserve volume (ERV)
Residual volume (RV)

Answer

A

Inspiratory reserve volume (IRV)
- Air that can still be breathed in after normal inspiration
Tidal volume (TV)
- Air that moves into lung with each quiet inspiration
- Typically 500 mL
Expiratory reserve volume (ERV)
- Air that can still be breathed out after normal expiration
Residual volume (RV)
- Air in lung after maximal expiration
- Cannot be measured on spirometry
Lung volumes (LITER):
- IRV
- TV
- ERV
- RV

Question 8

Q

Lung capacities

Inspiratory capacity (IC)
Functional residual capacity (FRC)
Vital capacity (VC)
Total lung capacity (TLC)
Capacity

Answer

A

Inspiratory capacity (IC)
- IRV + TV
Functional residual capacity (FRC)
- RV + ERV
- Volume in lungs after normal expiration
Vital capacity (VC)
- TV + IRV + ERV
- Maximum volume of gas that can be expired after a maximal inspiration
Total lung capacity (TLC)
- IRV + TV + ERV + RV
- Volume of gas present in lungs after a maximal inspiration
Capacity
- A capacity is a sum of ≥ 2 volumes.

Question 9

Q

Determination of physiologic dead space

Definition
Equation

Answer

A

Definition
- Anatomic dead space of conducting airways plus functional dead space in alveoli
- Apex of healthy lung is largest contributor of functional dead space.
- Volume of inspired air that does not take part in gas exchange.
Equation
- VD = VT × [(Pa_CO2 – Pe_CO2) / Pa_CO2]
  - Taco, Paco, Peco, Paco (refers to order of variables in equation)
- VT = tidal volume
- Pa_CO2 = arterial P_CO2
- Pe_CO2 = expired air P_CO2

Question 10

Q

Ventilation

For each
- Definition
- Equation
Minute ventilation (VE)
Alveolar ventilation (VA)

Answer

A

Minute ventilation (VE)
- Total volume of gas entering the lungs per minute
- VE = VT × respiratory rate (RR)
Alveolar ventilation (VA)
- Volume of gas per unit time that reaches the alveoli
- VA = (VT - VD) × RR

Question 11

Q

Lung and chest wall

Tendencies
- Lungs
- Chest wall
- What determines their combined volume
At FRC
- System pressure
- Airway and alveolar pressures
- Intrapleural pressure
- Pulmonary vascular resistance (PVR)
Compliance
- Definition
- Decreased in…
- Increased in..

Answer

A

Tendencies
- Lungs to collapse inward
- Chest wall to spring outward.
- Elastic properties of both chest wall and lungs determine their combined volume
At FRC
- Inward pull of lung is balanced by outward pull of chest wall, and system pressure is atmospheric.
- Airway and alveolar pressures are 0
- Intrapleural pressure is negative (prevents pneumothorax).
- Pulmonary vascular resistance (PVR) is at minimum.
Compliance
- Change in lung volume for a given change in pressure
- Decreased in pulmonary fibrosis, pneumonia, and pulmonary edema
- Increase in emphysema and normal aging.

Question 12

Q

Hemoglobin (Hb)

Hemoglobin
- Composition
- Forms
- Effect of increased Cl-, H+, CO2, 2,3-BPG, and temperature
Fetal Hb
- Composition
- Difference

Answer

A

Hemoglobin
- Composed of 4 polypeptide subunits (2 α and 2 β)
- Exists in 2 forms
  - T (taut) form has low affinity for O2.
    - Taut in Tissues.
  - R (relaxed) form has high affinity for O2 (300×).
    - Hb exhibits positive cooperativity and negative allostery.
    - Relaxed in Respiratory tract.
- Effect of increased Cl-, H+, CO2, 2,3-BPG, and temperature
  - Increased Cl-, H+, CO2, 2,3-BPG, and temperature favor taut form over relaxed form
  - Shifts dissociation curve to right, leading to O2 unloading).
Fetal Hb
- 2 α and 2 γ subunits
- Has lower affinity for 2,3-BPG than adult Hb and thus has higher affinity for O2.

Question 13

Q

Hemoglobin modifications

Lead to…
Methemoglobin
- Definition
- Methemoglobinemia
- To treat cyanide poisoning
Carboxyhemoglobin
- Definition
- Causes…

Answer

A

Lead to tissue hypoxia from decreased O2 saturation and decreased O2 content.
Methemoglobin
- Definition
  - Oxidized form of Hb (ferric, Fe3+) that does not bind O2 as readily, but has increased affinity for cyanide.
  - Iron in Hb is normally in a reduced state (ferrous, Fe2+).
    - Just the 2 of us: ferrous** is Fe_2+_.**
- Methemoglobinemia
  - May present with cyanosis and chocolate-colored blood.
- To treat cyanide poisoning
  - Use nitrites to oxidize Hb to methemoglobin, which binds cyanide.
    - Nitrites cause poisoning by oxidizing Fe2+ to Fe3+.
  - Use thiosulfate to bind this cyanide, forming thiocyanate, which is renally excreted.
  - Methemoglobinemia can be treated with methylene blue.
Carboxyhemoglobin
- Definition
  - Form of Hb bound to CO in place of O2.
  - CO has 200× greater affinity than O2 for Hb
- Causes…
  - Decreased oxygen-binding capacity with a left shift in the oxygen-hemoglobin dissociation curve.
  - Decreased O2 unloading in tissues.

Question 14

Q

Oxygen-hemoglobin dissociation curve

Shape
- Hemoglobin
- Myoglobin
Curve shifts
- Right
- Left
- Fetal Hb

Answer

A

Shape
- Hemoglobin
  - Sigmoidal shape due to positive cooperativity
  - i.e., tetrameric Hb molecule can bind 4 O2 molecules and has higher affinity for each subsequent O2 molecule bound.
- Myoglobin
  - Monomeric and thus does not show positive cooperativity
  - Curve lacks sigmoidal appearance.
Curve shifts
- An increase in all factors (including H+) causes a shift of the curve to the right.
  - When curve shifts to the right, decrease affinity of Hb for O2 (facilitates unloading of O2 to tissue)
  - Right shift—BAT ACE:
    - BPG (2,3-BPG)
    - Altitude
    - Temperature
    - Acid
    - CO2
    - Exercise
- A decrease in all factors (including H+) causes a shift of the curve to the left
- Fetal Hb has a higher affinity for O2 than adult Hb, so its dissociation curve is shifted left

Question 15

Q

Oxygen content of blood

Hb
- Normal
- Cyanosis
O2 content vs. saturation
Equations
- O2 content
- O2 delivery to tissues

Answer

A

Hb
- Normal
  - Normally 1 g Hb can bind 1.34 mL O2
  - Normal Hb amount in blood is 15 g/dL.
  - O2 binding capacity ≈ 20.1 mL O2/dL
- Cyanosis
  - Results when deoxygenated Hb > 5 g/dL.
O2 content vs. saturation
- O2 content of arterial blood decreases as Hb falls
- O2 saturation and arterial Po2 do not
Equations
- O2 content = (O2 binding capacity × % saturation) + dissolved O2
- O2 delivery to tissues = cardiac output × O2 content of blood

Question 16

Q

Oxygen content of blood

For each (increased/decreased)
- Hb level
- % O2 sat of Hb
- Dissolved O2 (PaO2)
- Total O2 content
CO poisoning
Anemia
Polycythemia

Answer

A

CO poisoning
- Hb level: Normal
- % O2 sat of Hb: Decreased (CO competes with O2)
- Dissolved O2 (PaO2): Normal
- Total O2 content: Decreased
Anemia
- Hb level: Decreased
- % O2 sat of Hb: Normal
- Dissolved O2 (PaO2): Normal
- Total O2 content: Decreased
Polycythemia
- Hb level: Increased
- % O2 sat of Hb: Normal
- Dissolved O2 (PaO2): Normal
- Total O2 content: Increased

Question 17

Q

Pulmonary circulation (599)

System
- Normally…
- Po2 and Pco2
- A decrease in PAo2 causes…
Limitations
- Perfusion limited
- Diffusion limited

Answer

A

System
- Normally a low-resistance, high-compliance system.
- Po2 and Pco2 exert opposite effects on pulmonary and systemic circulation.
- A decrease in PAo2 causes a hypoxic vasoconstriction that shifts blood away from poorly ventilated regions of lung to well-ventilated regions of lung.
Limitations
- Perfusion limited
  - O2 (normal health), CO2, N2O.
  - Gas equilibrates early along the length of the capillary.
  - Diffusion can be increased only if blood flow increases.
- Diffusion limited
  - O2 (emphysema, fibrosis), CO.
  - Gas does not equilibrate by the time blood reaches the end of the capillary.

Question 18

Q

Pulmonary circulation (599)

A consequence of pulmonary hypertension
Diffusion equation
Diffusion pathologies
- Area
- Thickness

Answer

A

A consequence of pulmonary hypertension
- Cor pulmonale
- Subsequent right ventricular failure (jugular venous distention, edema, hepatomegaly).
Diffusion equation
- Vgas = (A / T) × Dk (P1 – P2)
- A = area
- T = thickness
- Dk (P1 – P2) ≈ difference in partial pressures
Diffusion pathologies
- Area decreased in emphysema.
- Thickness increased in pulmonary fibrosis.

Question 19

Q

Pulmonary vascular resistance

PVR equation
Resistance equations

Answer

A

PVR = ( P_{pulm artery} – P_{L atrium} ) / cardiac output
- P_{pulm artery} = pressure in pulmonary artery
- P_{L atrium} = pulmonary wedge pressure
Resistance equations
- ΔP = Q × R
- R = ΔP / Q
- R = 8ηl / πr⁴
  - η = viscosity of blood
  - l = vessel length;
  - r = vessel radius

Question 20

Q

Alveolar gas equation

PAo2 equation
A-a gradient
- Equation
- Definition

Answer

A

PAo2 = PIo2 – (Paco2 / R) ≈ 150 – (Paco2 / 0.8)
- PAo2 = alveolar Po2 (mmHg).
- PIo2 = Po2 in inspired air (mmHg).
- Paco2 = arterial Pco2 (mmHg).
- R = respiratory quotient = CO2 produced / O2 consumed.
A-a gradient
- A-a gradient = PAo2 – Pao2 = 10–15 mmHg.
- Definition
  - Increased A-a gradient may occur in hypoxemia
  - Causes include shunting, V/Q mismatch, fibrosis (impairs diffusion).

Question 21

Q

Oxygen deprivation

For each
- Definition
- Due to…
Hypoxemia
- Normal A-a gradient
- Increased A-a gradient
Hypoxia
Ischemia

Answer

A

Hypoxemia
- Definition
  - Decreased Pao2
- Due to…
  - Normal A-a gradient
    - High altitude
    - Hypoventilation
  - Increased A-a gradient
    - V/Q mismatch
    - Diffusion limitation
    - Right-to-left shunt
Hypoxia
- Definition
  - Decreased O2 delivery to tissue
- Due to…
  - Decreased cardiac output
  - Hypoxemia
  - Anemia
  - CO poisoning
Ischemia
- Definition
  - Loss of blood flow
- Due to…
  - Impeded arterial flow
  - Decreased venous drainage

Question 22

Q

V/Q mismatch

Ideal V/Q
V/Q in lung zones
- Apex
- Base
- Comparison
V/Q with exercise
Limits
- V/Q –> 0
- V/Q –> ∞

Answer

A

Ideal V/Q
- Ideally, ventilation is matched to perfusion (i.e., V/Q = 1) in order for adequate gas exchange.
V/Q in lung zones
- Apex
  - V/Q = 3 (wasted ventilation)
- Base
  - V/Q = 0.6 (wasted perfusion)
- Comparison
  - Both ventilation and perfusion are greater at the base of the lung than at the apex of the lung.
  - Certain organisms that thrive in high O2 (e.g., TB) flourish in the apex
V/Q with exercise
- With exercise (increased cardiac output), there is vasodilation of apical capillaries, resulting in a V/Q ratio that approaches 1.
Limits
- V/Q –> 0 = airway obstruction (shunt).
  - In shunt, 100% O2 does not improve Po2.
- V/Q –> ∞ = blood flow obstruction (physiologic dead space).
  - Assuming < 100% dead space, 100% O2 improves Po2.

Question 23

Q

CO2 transport

CO2 is transported from tissues to the lungs in 3 forms:
In lungs
In peripheral tissue

Answer

A

CO2 is transported from tissues to the lungs in 3 forms:
- HCO3- (90%).
  - Majority of blood CO2 is carried as HCO3- in the plasma
- Carbaminohemoglobin or HbCO2 (5%).
  - CO2 bound to Hb at N-terminus of globin (not heme).
  - CO2 binding favors taut form (O2 unloaded).
- Dissolved CO2 (5%).
In lungs
- Oxygenation of Hb promotes dissociation of H+ from Hb.
- This shifts equilibrium toward CO2 formation
- Therefore, CO2 is released from RBCs (Haldane effect).
In peripheral tissue
- Increased H+ from tissue metabolism shifts curve to right, unloading O2 (Bohr effect).

Question 24

Q

Response to high altitude

Atmospheric oxygen
Ventilation
Erythropoietin
2,3-BPG
Mitochondria
Renal excretion of HCO3-
Pulmonary

Answer

A

Decreased atmospheric oxygen –> decreased Pao2 –> increased ventilation –> decreased Paco2.
Chronic increase in ventilation.
Increased erythropoietin –> increased hematocrit and Hb (chronic hypoxia).
Increased 2,3-BPG (binds to Hb so that Hb releases more O2).
Cellular changes (increased mitochondria).
Increased renal excretion of HCO3- (e.g., can augment by use of acetazolamide) to compensate for the respiratory alkalosis.
Chronic hypoxic pulmonary vasoconstriction results in RVH.

Question 25

Q

Response to exercise

CO2 production
O2 consumption
Ventilation rate
V/Q ratio
Pulmonary blood flow
pH
Pao2
Paco2
Venous CO2 content
Venous O2 content

Answer

A

Increased CO2 production.
Increased O2 consumption.
Increased ventilation rate to meet O2 demand.
V/Q ratio from apex to base becomes more uniform.
Increased pulmonary blood flow due to increased cardiac output.
Decreased pH during strenuous exercise (2° to lactic acidosis).
No change in Pao2
No change in Paco2
Increase in venous CO2 content
Decrease in venous O2 content.

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Respiratory - Anatomy and Physiology Flashcards

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