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Organ System Anatomy, Physiology and Pathology - BPT06 > Respiratory Physiology > Flashcards

Respiratory Physiology Flashcards

1
Q

Functions of the Respiratory System

A
  1. Provide oxygen to body tissue
  2. Remove carbon dioxide
  3. Help maintain pH balance
  4. Sensing odors
  5. Voice production
  6. Defense against pathogens
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2
Q

Main Function of Respiratory System

A

Pulmonary ventilation: inspiration and expiration
Gas exchange between air and blood
Transportation of gases to tissues
Gas exchange between the blood and tissues

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3
Q

Systemic Respiration

A

Exchange of O2 and CO2 between atmosphere and body tissues

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4
Q

Aerobic Respiration

A

Takes place in mitochondria and requires oxygen and glucose, producing carbon dioxide, water and ATP.
C6H12O6 + 6O2 → 6CO2 + 6H2O

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5
Q

External Respiration

A 
PalvO2 = 104 mmHg, PcapO2 = 40 mmHg
PalvCO2 = 40 mmHg, PcapCO2 = 45mmHg (small gradient, high solubility)
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6
Q

Internal Respiration

A

PtissueO2 = 40 mmHg, PcapO2 = 100 mmHg

PtissueCO2 > PcapCO2

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7
Q

Medullary Respiratory Centers

A

Clustered neurons in two areas of the medulla oblongata appear to be critically important in respiration:

  • Dorsal respiratory group (DRG)
  • Ventral respiratory group (VRG)
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8
Q

Dorsal Respiratory Group

A

Integrates input from peripheral stretch and chemoreceptors and communicates this info to VRG.

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9
Q

Ventral Respiratory Group

A

Rhythm generating.
When inspiratory neurons fire:
- Impulses travel along phrenic and intercostal nerves to excite diaphragm and external intercostal muscles.
- Thorax expands and air rushes in lungs.
When expiratory neurons fire:
- Output stops
- Passive expiration, inspiratory muscles relax, lungs recoil.

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10
Q

Pontine Respiratory Center

A

Transmit impulses to VRG of medulla.
Modifies and fine tunes breathing rhythms generated by VRG during certain activities such as vocalization, sleep and exercise.

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11
Q

Neural Influences - hypothalamic vs cortical control

A

Hypothalamic Controls: Emotions and pain send signals to respiratory centers, modifying respiratory rate and depth.
Cortical Controls: Breathing normally regulated involuntarily in brain stem, can also exert conscious control over rate and depth.

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12
Q

Respiratory Pressure - Expiration

A
  • Expiration: Alveoli volume decreases, Palv increases.
    Patm < Palv → Air moves out of lungs until pressures are equal again.
  • End of expiration: Patm = Palv → No air movement
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13
Q

Pressure Gradient that Drives Ventilation

A

Palv - Patm

Intrapulmonary pressure - Atmospheric pressure

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14
Q

Respiratory Pressure - Inspiration

A
  • Inspiration: Alveoli volume increases, Palv decreases. Patm > Palv → Air moves in to lungs.
  • End of inspiration: because of the airflow into lungs Patm = Palv → No air movement.
    Diaphragm and external intercostal muscles contract, expansion of thoracic cavity stretches lungs: volume increases, pressure decreases.
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15
Q

Atmospheric Pressure

A

760 mmHg at sea level - constant.

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16
Q

Intrapleural Pressure (Pip)

A

Pressure in pleural cavity.
Decreases with inhalation
Increases with exhalation
Pip < Palv (always negative compared to Palv)
Negative Pip created by: tendency of thorax to expand outwards, tendency of lungs to recoil (elasticity). Intrapleural fluid keeps it from pulling apart.

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17
Q

Transpulmonary Pressure

A

Difference between alveoli pressure and pleura pressure.
Palv - Pip
Increasing transpulmonary pressure → expansion of alveoli

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18
Q

Alveolar Volume

A

Alveoli on top always inflated, on bottom no because: gravity and weight of lung increase pleural pressure (less negative) at the base of the lung and thus reducing alveolar volume.

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19
Q

Dependent Region on Lungs

A

Lowest part of lung in relation to gravity (bottom lung in side-lying position). Alveoli will inflate in this region.

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20
Q

Boyle’s Law

A

Pressure inversely related to its volume (under constant temperature in closed system.
Pressure ↑ → Volume ↓
Pressure ↓ → Volume ↑
Gas moves from high pressure region to low pressure region.

21
Q

Breathing

A

Process in which the respiratory pump creates ventilation.

22
Q

Respiration

A
  1. Exchange of gas between the environment and tissue cells, by external respiration at alveola-capillary level and internal respiration at capillary- tissue level.
  2. Regulation of the acid-base, metabolic and defense functions of the respiratory system.
23
Q

Ventilation

A

Gas movement between the outside and the alveoli.

Ventilation (L/min) = volume (L) x frequency (breaths per minute) → 0,5 L(tidal volume) x 10 (normal frequency) = 5L.

24
Q

Conducting Zone

A

No alveoli. No gas exchange. 150ml out of the 500 will stay in this area. Only 350ml will reach the alveoli.
Dead space ventilation.

25
Q

Alveolar Ventilation (VA)

A

RR x (VT - DSV) : Respiratory rate x (tidal volume - dead space ventilation).
During exercise: VA must increase → increased VT
Determines O2 and CO2 levels
VA ↓ → PaCO2 ↑: acid-base balance disturbance, hypoxemia/hypercapnia.

26
Q

Dead Space Ventilation

A

Wasted ventilation in conducting zone.
Anatomic dead space: conducting part of respiratory tract. 150 ml of VT.
Physiological dead space: anatomic + alveolar dead space (alveoli not taking part in gas exchange).

27
Q

Collateral Ventilation

A

Network connection between alveoli. If alveoli is not ventilating, the collateral channel will open.

  • Interalveolar pores of Kohn
  • Interbronchial channels
  • Bronchiole-alveolar channels
28
Q

Hyperventilation

A

incresing of the exhaled volume (VE) that eliminates carbon dioxide leading to hypocapnea.
Related to ventilation not respiratory frequency.

29
Q

Hypoventilation

A

Reduce alveolar ventilation due to reduced tidal
volume (VT) followed by hypercapnea. Short breaths.
Related to ventilation, not to respiratory frequency.

30
Q

Tachypnoea

A

increased RR > 20 breaths/min.

Cannot breath slowly.

31
Q

Bradypnoea

A

decreased RR < 10 breaths/min.

32
Q

Apnea

A

Cessation of breathing (more than 30 sec)

33
Q

Laminar Flow

A

Facilitated by slow smooth breath.
In order to overcome peripheral resistance to reach alveoli with least amount of energy.
Fast breath encourages unhelpful turbulence.

34
Q

What are the physical factors influencing pulmonary ventilation?

A
  • Airway resistance
  • Lung compliance
  • Alveolar surface tension (pulmonary surfactant)
35
Q

Airway Resistance - Poiseuille’s law

A 
Resistance (R) through an airway depends on:
• Viscosity (ƞ) of gas
• Length of tube (l)
• Radius of tube (r)
↑ diameter  →  ↑ resistance 
↑ length of tube  →  ↑ resistance
↑ viscosity of gas  →  ↑ resistance
36
Q

Consequences of Increased Airway Resistance

A

↓ airway caliber
↓ airflow
↑ work of breathing
Breathlessness

37
Q

Work of Breathing (WOB)

A

Work done during inspiration to overcome resistive and elastic forces of airways, lungs and chest wall.
Elastic resistance: 80% of WOB (deep breathing)
Airflow resistance: 20% of WOB (rapid breathing)

38
Q

Compliance

A

Willingness of elastic structure to distend (change its state).
Lung is least compliant at either extreme of lung volume.
- Difficult to inflate closed alveoli
- Difficult to hyperinflate those that are fully inflated.

39
Q

Pulmonary Surfactant

A

surface-active lipoprotein complex formed by Type II pneumocytes.
Reduces the surface tension inside alveoli.
Cannot ventilate without it! Alveoli will collapse.

40
Q

Lung Volumes - VT, ERV, IRV, RV

A
  • Tidal Volume (VT): movement of air during quite breathing, 0.5 L.
  • Expiratory reserve volume (ERV): Extra air pushed out of lungs beyond VT after full exhalation. 1.7 L.
  • Inspiratory reserve volume (IRV): extra air drawn in beyond VT after full inhalation. 3 L.
  • Residual volume (RV): air remaining in lungs after full exhalation. 1.3 L.
41
Q

Total Lung Capacity

A

Sum of lung volumes. Total air in lungs after full inhilation.
VT+ERV+RV+IRV

42
Q

Fick’s Law of Diffusion

A 
Diffusion (gas exchange):
• Concentration / pressure gradient
• Gas solubility
• Transit time red blood cells (RBC)
• Surface area of alveolar membrane
• Thickness of alveolar membrane
• Ventilation/perfusion coupling
43
Q

Thickness of Alveocapillary Membrane

A

0.5 - 1 u(mju)m - very efficient

Thicker membrane → impaired diffusion → ↓O2

44
Q

Essential Components for Gas Exchange

A

• V̇ : air which reaches lungs (alveolar ventilation)
• Q̇ : blood which reaches lungs (alveolar perfusion)
V̇ / Q̇ : matching between (alveolar) ventilation and perfusion

45
Q

Zones of Gas Exchange

A
  1. Alveoli (full volume) squeezes capillary. Pressure of alveoli is bigger than pressure of artery and vein.
    PA > Pa > Pv - No gas exchange. Top part of lung.
  2. Depends on cardiac cycle. Psystolic > PA > Pdiastolic.
    Gas exchange possible during systole. 50% efficient. Middle part of lung
  3. Artery and vein pressure more than alveoli.
    Pa > Pv > PA. Gas exchange. 100% efficient. Bottom part, dependent zone.
46
Q

Shunt vs. Dead Space

A

No gas exchange in either.
Dead space: Alveoli ventilating without perfusion (gas exchange).
Shunt: Fraction of blood not getting oxygen (no gas exchange).

47
Q

Pathological Mismatch - Ventilation/Perfusion

A

V/Q should be equal to 1.
Pathological mismatch is due to a high or low ratio
• High ratio : alveoli ventilated but perfusion impaired - V/Q = 5/0 = infinite.
• Low ratio : lung perfused but not adequately ventilated - V/Q = 0/5 = 0.

48
Q

V/Q Regulation

A

V: regulated by diameter airways
Q: regulated by diameter blood vessels

Organ System Anatomy, Physiology and Pathology - BPT06 (34 decks)

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