Respiratory System, Lecture 1

Question 1

4 Components of Respiratory System

Answer 1

ventilation
- air exchange between atmosphere (air surrounding the body) and alveoli (where exchange takes place)

gas exchange:
- external respiration: gas exchange between alveoli and pulmonary capillaries (lung level)
◦ can move both ways alveoli <-> pulmonary capillaries
- internal respiration: gas exchange between tissue capillaries and tissue cells (tissue level)
◦ interstitial fluid that will take it to the tissue cell that can be considered two exchanges

gas transport:
- gas movement via pulmonary and systemic circulations

Question 2

Ventilation - general

Answer 2

• at sea level atmospheric pressure varies; typically ~760mmHg (not always that value as it fluctuate daily)
• often report pressure changes relative to sea level value (if a value is not given use 760 as your zero value where things add or subtract from there)
• air moves by pressure gradient:
  ◦ breath in - inspiration/inhalation - atmosphere (high pressure) to lungs (low pressure)
  ◦ breath out - expiration/exhalation - lungs (high pressure) to atmosphere (low pressure)
  ◦ between breaths - pressures equalize between lungs and atmosphere; no air movement for a moment
• atmospheric pressure variable and not in control of
• need to manipulate pressure at lung level to give needed pressure gradient

Question 3

Ventilation - Boyle’s law

Answer 3

• in a closed system at constant temperature, pressure (P) and volume (V) are inversely proportional (P ∝ 1/v)
  ◦ decrease volume - increase pressure
  ◦ increase volume - decrease pressure
• volume changes - pressure changes - pressure gradient - air flow

Question 4

Ventilation - pressures

Answer 4

pressures:
- atmospheric (Patm):
◦ environment surrounding body/also known as air or barometric pressure
- alveolar (Palv):
◦ within alveoli
- intrapleural pressure (Pip)
◦ inside intrapleural space (pleura that layers outer/inner of lungs (o) and inner chest wall (i) and this is the space between it) /always subatmospheric (lower than Patm) (always a negative value - not a consistent negative (more or less))
do not have to memorize numbers but can be helpful (roughly -4)
* subatmospheric pressure is what allows for the recoils to stay in a position instead of doing what they want to do

Question 5

Ventilation - inspiration (normal, quiet breathing)

Answer 5

normal, quiet breathing:
- diaphragm (75% responsible)
◦ contraction - downward flattening (~2cm)
- external intercostals (25% responsible)
◦ contraction - outward movement of chest wall

Question 6

Ventilation - inspiration (more forceful breathing)

Answer 6

more forceful breathing:
- diaphragm
◦ contraction - stronger; more downward flattening (up to 10 cm)
- external intercostals
◦ contraction - stronger; more outward movement of chest wall
- accessory muscles of inspiration recruited (scalenes, sternocleidomastoid, pectoralis minor)
◦ contraction - more outward movement of chest wall
- result
◦ greater increase in lung volume
◦ Palv decreases below atmospheric to greater extent (larger pressure gradient)
◦ even more air flows to lungs

Question 7

Ventilation - expiration (normal, quiet breathing)

Answer 7

normal, quiet breathing:
- muscle stop contracting; recoil to pre-inspiration positions/pressures
- diaphragm
◦ no contraction - rises back to dome shape
- external intercostals
◦ no contraction - inward movement of chest wall

Question 8

Ventilation - expiration (more forceful breathing)

Answer 8

more forceful breathing
- diaphragm
◦ no contraction - rises back to dome shape
- external intercostals
◦ no contraction - inward movement of chest wall
- accessory muscles of expiration recruited (internal intercostals, abdominals)
◦ contraction - more inward movement of chest wall
result
- greater decrease in lung volume; more compression of alveoli
- Palv increases beyond atmospheric to greater extent (larger pressure gradient)
- even more air flows out of lung