Ventilation and perfusion Flashcards
Describe the conducting zone of the respiratory system
trachea to the bronchioles
where there is no gas exchange
Describe the respiratory zone of the respiratory system
respiratory bronchioles to the alveoli
where there is gas exchange
How does inspiration occur
- Diaphragm contracts and flattens and moves caudally
- Ribs are pulled cranially and outwards by contraction of the external intercostal muscles
- Together these increase the volume of the thoracic cavity, decreasing the pressure of the air in the alveoli and causing air to be sucked in as air flows from high to low pressure
How does expiration occur
- Is a passive response except during exercise
- The diaphragm relaxes and raises
- intercostal muscles relax and ribs and sternum go down
Describe the composition of the diaphragm
central part= tendinous
Peripheral = muscular
What is the diaphragm attached to
- xiphoid process
- lower costal cartilages
- ribs
- vertebral column
Describe the crura of the diaphragm
right and left crus or fibromuscular bands arising from the ;lumbar vertebrae, insert into the central tendon of the diaphragm
Name the 3 things that pass through the diaphragm
- oesophagus
- aorta
- vena cava
What nerve innervates the diaphragm
phrenic nerve
Where do external intercostal muscles lie
superficially and the fibres run caudoventrally between ribs
where do internal intercostal muscles lie
lie underneath and fibres run in the opposite direction
Name the 2 components of internal intercostal muscles
interosseous
interchondral
Describe the interosseous part of the internal intercostal muscles
expiratory muscles between bones
describe the interchondral part of the internal intercostal muscles
inspiratory muscles between cartilage
Describe the parietal pleura
outer layer of pleura lying closer to the ribs and chest wall
Describe the visceral pleura
inner layer of pleura lying closer to the lung tissue
Describe the pleural cavity
the space between the folds of the pleura
how does locomotion affect ventilation
stride cycle and ventilation cycle of galloping animals are synchronized, piston pendulum theory, movement of the limbs influences inspiration and expiration, inspiration only when the body is extended due to negative pressure in the thorax
What are the factors influencing ventilation
- resistance to flow in the airways
- lung compliance
- alveolar surface tension
What is the calibre or airways
internal diameter
What are the smooth muscles of the airway walls
bronchial muscle- musculus spiralis
describe the laminar flow
a smooth pattern of flow
describe turbulent flow
irregular flow with random variations in pressure
Where is turbulence greatest
in trachea and bronchi
what is compliance
change in volume of a structure for eac unit change in pressure
what is elastance
retractive (recoil) force that the distension of a structure generates
How is surface tension in the alveoli reduced
surfactant
how is the pressure inside the alveolus determined
by the surface tension of the lining fluid and the radius of the alveolus
Why is surfactant more concentrated in smaller alveoli
the surface tension is higher in smaller alveoli
Define tidal volume
Is the amount of air breathed in or out during a respiratory cycle. It can increase or decrease from normal depending on ventilation requirements
Define inspiratory reserve volume
is the amount of air that can still be inspired after inhaling the tidal volume
Define expiratory reserve volume
is the amount of air that can still be expired after exhaling the tidal volume
Define residual volume
is the amount of air remaining in the lungs after the most forceful expiration
Define inspiratory capacity
is the sum of the tidal and inspiratory reserve volumes
Define vital capacity
the greatest volume of air that can be expelled from the lungs after taking the deepest possible breath
Define functional residual capacity
Is the sum of the expiratory reserve volume and the residual volume
Define total lung capacity
Is the entire gas volume of the maximally spontaneously inflated pulmonary parenchyma and airways in the thorax
Define respiratory rate
Is the rate at which breathing occurs. This is usually measured in breaths per minute
Define minute ventilation
Is the total volume of gas moved in or out of the airways and alveoli in 1 minute
Define dead space
Is the volume of air that is inhaled that does not take part in the gas exchange, because it either remains in the conducting airways or reaches alveoli that are not perfusion or poorly perfused
Define alveolar ventilation
Is defined as the volume of air entering and leaving the alveoli per minute
Describe the regional differences in ventilation
lower portions of the lung are ventilated more than upper zones
What is pulmonary perfusion
blood flow to the alveoli allowing uptake of oxygen and removal of carbon dioxide
list 4 factors affecting perfusion
- hypoxic vasoconstriction
- disease
- posture
- cardiac function
Describe hypoxic vasoconstriction
reduces blood flow to the alveoli that aren’t being ventilated in order to send blood to ventilated areas
What is ventilation and perfusion mismatch
where the ventilation and perfusion don’t match and aren’t even across the lung
Describe the V/Q at base of lung
low as there is more blood flow than ventilation
Describe the V/Q at apex of the lung
high as there is more ventilation than blood flow
Describe mismatching of ventilation due to posture
ventilation is less in dorsal areas and can become restricted when the animal is lying down due to the lungs becoming crushed
Explain how ventilation is regulated
Is regulated by the respiratory centre in the medulla, which generates action potentials, modulated by feedback from:
- Chemorecptors
- Mechanorecptors
