18 - anatomy of ventilation Flashcards
pulmonary ventilation definition:
the physical movement of air into and out of the respiratory tract
function of breathing:
to ensure constant supply of oxygen
to prevent build up of CO2 and therefore maintain pH
inspiration
expiration
inhilation
exhalation
what two principles does pulmonary ventilation rely on?
- Boyles law (pressure of a gas is inversley proportional to its volume (and so the containers volume) at a constant temperature)
- Air flows from an are of low pressure to an area if high pressure
In a syringe
- plunger pulled back
- volume inside increases
- pressure decreases
- fluid/gas moves in
air will enter the lungs when
atmospheric pressure is greater than pressure within the lungs (intraalveolar pressure or intrapulmonary pressure)
air will leave the lungs when
atmospheric pressure is less than pressure in the lungs
how do we change the pressure in the lungs?
by changing the volume of the lungs and thoracic cavity
atmospheric pressure is
760mmHg
pressure in the lungs differs by how many mmHg during inspiration and expiration
-1=759
+1=761
Thoracic volume can be increased by:
-increasing the vertical diameter (diaphragm)
-increasing the anterior posterior diameter (ribs)
-increasing the transverse diameter (up and out) (ribs)
not horizontal diameter
contracting the diaphragm
- flattens the diaphragm
- causes vertical diameter to increase
- increases thoracic capacity by 75%
Elevation of the ribs
- increases the AP diameter and the transverse diameter
- responsible for 25% of thoracic capacity increase
How is AP diameter increased
- pump handle action of the ribs
- elevation of the ribs at the sternal end causes them to become horizontal instead of B\F
How is the transverse diameter increased
The bucket handle - ribs tend to dip in the middle like a sagging bucket handle - during inspiration pick the bucket handle up so its horizontal - this increases the diameter from left to right
How does the thoracic cavity size effect lung size?
The parietal pleura is stuck to the thoracic wall and diaphragm.
the visceral pleura is stuck to the surface of the lungs and moves with the parietal pleura due to surface tension cause by the serous fluid (fills cavities) in the cavity between the two membranes
the pressure in the pleural cavity is
always lower than atmospheric and intrapulmonary pressure because the elastic fibres in the lung tissue are always trying to pull back and cause recoil, causing negative pressure in the pulmonary cavity
If air gets between lung and _____ pleura
- parietal pleura the lung will succeed on pulling back and come free from the pleura and collapse - pneumothroax
- occurs as a result of injury - disease or puncture wound
what causes pneumothorax
- accumulation of air in pleural cavity resulting from disease or puncture wound
- loss of negative intrapleural pressure
- lung collapse
on x-rays what is
- black
- white
- imbetween
- air is black
- connective tissues come up faintly grey
- if the whole lung space is a solid black colour the lung has collapsed
- bone is white
- everything else is imbetween
when one lung collapses
it can push the mediastinum to the other side and cause the other lung to collapse
what to do when someones lung collapses
put a tube into the pleural cavity and put the other end of the tube into water so the air from the space will start bubbling into the water and the lung will re-inflate
what is used in quiet inspiration
active process
- diaphragm 75%
- external intercostal muscles 25%
