Physiology 1 - Respiratory mechanisms Flashcards
4 steps if respiration/gas exchange/external respiration.
1) ventilation
2) gas exchange between atmosphere & alveoli
3) gas transport in the blood
4) gas exchange at tissue level
2 structures where air enters the lung.
1) trachea
2) bronchial tree
property of the trachea that allows swallowing?
elasticity of the trachea
property of hyaline cartilage that prevents trachea from collapsing during inspiration
curved rings of hyaline cartilage
why mucus covers the trachea & bronchial tree?
to trap dirt, dust & inspired particles
describe cilia’s role in the clearance of these particles.
beats the trapped dust & particles upwards towards the larynx.
Once they reach the larynx, larger particles are expelled by coughing, smaller particles are tipped into the oesophagus.
why does air flow from the atmosphere into the alveoli?
due to a difference in pressure created by the contraction & relaxation of respiratory muscles.
What is Boyle’s Law?
the volume of gas is inversely proportional to the pressure of the gas
what is the pressure differences between the atmosphere and intra-alveoli BEFORE INHALATION?
the intra-alveolar and atmospheric pressure are the SAME
what happens to the pressure during inhalation and why?
- for air to flow into the lungs, the intra-alveolar pressure must fall.
- the chest wall and lungs expand
- expansion of the lungs, increases volume of the alveoli & REDUCES the PRESSURE OF THE ALVEOLI
- therefore allowing air to enter the lungs
in order for lungs to expand on inspiration, what muscles contract on inspiration?
1) diaphragm
2) external intercostal muscles
What happens to the diaphragm when you contract it?
the diaphragm flattens
what happens to the vertical diameter of the thoracic cage when the diaphragm is contracted?
the vertical diameter of the thoracic cage is increased
describe the effect of contracting external intercostal muscles to the ribs and lateral and anterior-posterioir diameter of chest.
- ribs are elevated
- lateral and anterior-posterior diameter of the chest increases
name the 2 forces that hold the thoracic wall and lungs in close opposition.
1) intra pleural fluid cohesiveness
2) negative intra pleural pressure
describe intra pleural fluid cohesiveness
- water molecules in the intra pleural fluid are attracted to each other & resist being pulled apart
- hence, pleural membranes end to stick together
Describe the negative intra pleural pressure?
sub-atmospheric intra-pleural pressure creates a transmural pressure gradient across the lung wall & across the chest wall.
- so the lungs are forced to expand outwards while the chest is forced to squeeze inwards
is expiration passive or active?
Describe how expiration works?
PASSIVE
= no contraction necessary
- inspiratory muscles relax,
- recoil of the chest wall and lungs due to elastic connective tissue in the lungs
- alveolar surface tension produces a force which resists the stretching fo the lungs
- pressure in alveoli is higher than atmosphere so air is forced out of lungs as it moves up the trachea
is inspiration passive or active?
ACTIVE
is EXHALATION active of passive?
ACTIVE
what muscles contract during exhalation?
1) internal intercostal muscles
2) abdominal muscles
What does contraction of these muscles cause the ribs and diaphragm to do?
- inferior ribs move down
- diaphragm moves up
- the spaces between the ribs contract, increasing abdominal and thoracic pressure
What does surfactant do?
= reduces the alveolar surface tension, by interspersing between the water molecules lining the alveoli
Do smaller of larger alveoli have higher tendency to collapse?
smaller alveoli
- according to Law of LaPlace
what cells secret surfactant?
type II alveoli
what is alveolar interdependence?
- when one alveolus starts to collapse, the surrounding alveoli stretch & then recoil exerting expanding forces in the collapsing alveolus, causing it to open
