Lecture 16 Breathing / Ventilation Flashcards
Boyle’s Law
P = 1 / V
inverse relationship between pressure and volume
decrease volume = increase pressure
increase volume = decrease pressure
Between breaths – pressure inside the thoracic cavity =
pressure outside (no pressure gradient in to out) – No air movement
Change the pressure in one
air will move to lower pressure space
to breathe what do we need to establish to make air move?
pressure gradient
Changing the dimensions (volume) of the thorax, will change
pressure in the thorax, pressure in alveoli, and air will move
increase vol - air in
decrease vol - air out
Body Cavities
Pressure within a cavity
Change volume of the thorax
Change pressure
Greater or less than external air pressure
Air flows in or out
How is the volume of the thoracic cavity changed?
Boundaries of thorax
Movement of parts
- muscles
- joints
Thoracic cavity movement - pleura
what is Pleural fluid – thin film?
– Moist slippery surface – lung surface moves against other structures (diaphragm, thoracic wall)
– Holds lungs tight against thoracic wall – fluid bond between visceral and parietal pleura
thoracic wall movement results in lung movement
- Increase volume of thorax
- increase volume of lung
- decrease pressure in lung
- air flow in
Thoracic joints - anterior
- Sternum to ribs
- via costal cartilage (hyaline)
- Synovial joints
- Cartilaginous joints
sternocostal
costochondral
interchondral
Sternocostal
whats the joint?
- Synovial
- Except 1st = cartilaginous
Costochondral
whats the joint?
- cartilaginous
Interchondral
whats the joint?
- synovial
Thoracic joints – posterior
costotransverse
vostovertebral
- Articulation between thoracic vertebrae and ribs
- Synovial joints = movement
Muscles of Respiration - inspiration
- Diaphragm (main)
- Intercostals
- Accessory muscles
Quiet inspiration
active
• Diaphragm + external intercostals
• Active inspiration
- Add in accessory muscles
* Muscles which elevate ribs further
Muscles of Respiration - expiration
- Diaphragm
- Intercostals
- Accessory muscles (internal intercostal, abs)
Quiet expiration
passive
• diaphragm + external
intercostals relax
• elastic tissue recoil
• Active exhalation
Cough, if airway resistance is high, e.g. narrow airways in asthma
Muscles of Respiration - expiration
Add in accessory muscles
– Muscles which reduce depth + width of thoracic cavity
– Abs muscles contract – decrease volume of abdominal cavity – push diaphragm up
Inhalation –
volume increases (alveolar volume) Pout > Pinside - air flows in
Exhalation
volume decreases (alveolar volume) Pout < Pinside - air flows out
Summary: Breathing – thoracic volume changes
Contraction of diaphragm thoracic cavity length (75%)
Muscle (skeletal) - contract
Central tendon
