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6.4 Gas Exchange (lung capacity (factors affect (location, lifestyle,…
6.4 Gas Exchange
lung capacity
residual volume
Volume of air that is always present in the lungs (~ 20% of total lung capacity)
tidal volume
Volume of air that is exchanged via normal breathing (~ 500 ml per breath)
vital capacity
Volume of air that can be exchanged by the lungs via a maximal inhalation and exhalation
ventilation rate
breathing frequency
total lung capacity
Volume of air in the lungs after a maximal inhalation (~ 6 litres in a normal adult male)
factors affect
location
lifestyle
height
VO2 max
The maximum rate at which oxygen can be absorbed and supplied to body tissues
VO2
The volume of oxygen absorbed by the body per minute and supplied to the tissues
lung disorders
lung cancer
symptoms
coughing up blood, wheezing, respiratory distress and weight loss
factors
radiation, ageing, pollution,environments,diseases,genetics,occupation,asbestos,tobacco,smoke
uncontrolled proliferation of lung cells lead to tumour
emphysema
abnormal enlargement of the alveoli, leading to a lower total surface area for gas exchange
walls of the alveoli lose their elasticity due to damage
degradation of the alveolar walls can cause holes to develop and alveoli to merge into huge air spaces
major cause: smoking
The damage to lung tissue leads to the recruitment of phagocytes to the region, which produce an enzyme called elastase
This elastase, released as part of an inflammatory response, breaks down the elastic fibres in the alveolar wall
Elastase activity can be blocked by an enzyme inhibitor (α-1-antitrypsin), but not when elastase concentrations are increased
A small proportion of emphysema cases are due to a hereditary deficiency in this enzyme inhibitor due to a gene mutation
symptoms
shortness of breath, phlegm production, expansion of the ribcage, cyanosis and an increased susceptibility to chest infections
asthma
chronic inflammation of the airways to the lungs (i.e. bronchi and bronchioles)
pneumothorax
abnormal collection of gas in the pleural space that causes an uncoupling of the lung from the chest wall
VENTILATION :continually cycling fresh air into the alveoli from the atmosphere
GAS EXCHANGE:The exchange of oxygen and carbon dioxide between the alveoli and bloodstream (via passive diffusion)
CELL RESPIRATION : The release of energy (ATP) from organic molecules – it is enhanced by the presence of oxygen (aerobic)
measuring ventilation
simple observation
Chest belt and pressure meter
spirometer
breathing mechanism
Boyle's Law
pressure inversely proportional to volume
e.g :volume of the thoracic cavity , :arrow_up:: pressure in the thorax :arrow_down: (INHALATION) & vice versa for EXHALATION
effect of exercise
oxygen deficit :arrow_right: oxygen debt
:arrow_up:
ventilation rate
tidal volume
pneumocytes
pneumocyte I
involved in the process of gas exchange between the alveoli and the capillaries
minimising diffusion distance for respiratory gases
flattened) in shape and extremely thin (~ 0.15µm)
connected by occluding junctions(prevents leakage into alveolar air space
unable to replicate
pneumocyte II
cuboidal in shape & possess many granules (for storing surfactant components)
can differentiate into type I cells if required
secretion of pulmonary surfactant, which reduces surface tension in the alveoli
respiratory muscles
inspiration
core muscles
external intercostals
diaphragm
accessory muscles
pectoralis minor
sternocleidomastoid
mechanism
External intercostals contract, pulling ribs upwards and outwards (expanding chest)
Additional muscle groups may help pull the ribs up and out
Diaphragm muscles contract, causing the diaphragm to flatten and increase the volume of the thoracic cavity
expiration
core muscles
diaphragm
internal intercostals
accessory muscles
abdominal
quadratus lumborum
mechanism
vive versa to INSPIRATION :heavy_plus_sign:abdominal muscles contract and push the diaphragm upwards during forced exhalation
lung structure
