Respiratory physiology Flashcards
Upper respiratory system includes
Nose Naval cavity Sinuses Pharynx Larynx
What are trachea ?
Approx 20 horse shoe shaped cartilage
Trachealis muscle lines posterior wall for flexibility
Lined by columnar epithelial cells
Mucous stream upwards to carry debris
Cystic fibrosis
Multi system disease
Autosomal recessive inheritance
Causes mutation in cystic fibrosis transmembrane conductance regulator
Difference between right and left lung?
Right lung has 3 lobes
Left has 2
What are lungs lined with?
Pleura
Visceral pleura surround lungs
Parietal pleura attached to thoracic cavity
23 airway divisions from trachea to alveoli
Type 1 alveolar cells
Thin, flat accounting for wall lining
Microvilli
aid gaseous exchange
Type 2 alveolar cells
Thicker and less in number
Secrete surfactant
Surfactant
phospholipid and protein mixture
decreases surface tension
prevents alveoli collapsing
Respiratory membrane
Comprised of:
Squamous epithelial cell lining alveolus
Endothelial cell lining of capillaries
Gap membrane
Blood supply to lungs
Pulmonary artery
Lungs
Pulmonary Vein
Quiet breathing
Expiration results from passive recoil of lungs
External intercostal muscles
Found between ribs with fibres running downwards
Pull ribs together raising ribs up during inspiration
Internal intercostal muscles
Between ribs
Fibres run at right angles to external fibres
Depress rib cage during forced expirations
Boyle’ Law
The pressure of gas changes inversely with a change in volume
increased vol = decreased pressure
Pressure = 1 / volume
Atmospheric pressure
Variations will alter the amount of inspired oxygen available
Intra alveolar pressure
Pressure within alveoli
For air to flow in, pressure gradient must exist between atmosphere and alveoli
Intrapleural pressure
Pressure within pleural sac, usually less than atmospheric
Caused by recoil of lungs pulling on parietal pleura
Interpleural pressure
Elastic fibres try to collapse lung
parietal pleura pulled away from visceral
increased volume so decreased pressure
fluid bonds prevent total recoil
Pulmonary ventilation
Completely mechanical process dependent on volume change occurring in thoracic cavity
Mechanism of breathing
Air flows from region of high pressure to low pressure
Factors affecting ventilation
Gas flow - the ease which the lungs can be expanded
Lung compliance
Lung elasticity
Work of breathing
About 3% of total energy expenditure (100kcal per day)
COPD
Chronic Obstructive Pulmonary Disorder
caused by smoking
Includes bronchitis, emphysema
Bronchitis
Chronic cough
low PaO2 promotes desaturation
Emphysema
Prolonged expiration
Weight loss
Asthma
Characterised by intermittent periods of reversible airway obstruction leading to air flow problems
Type 1 hypersensitivity
allergen binds to IgE on surface of mast cells
Degranulation
Total lung capacity
70kg adult male
6L
Functional residual capacity
3L
Inspiratory capacity
3L
Residual volume
1.5L
Expiratory reserve volume
1.5L
Tidal volume
0.5L
Inspiratory reserve volume
2.5L
Minute volume
= VT x BR
Hypoventilation
inadequate removal of CO2 = acidosis
Hyperventilation
Excessive removal of CO2 = alkalosis
FVC
Forced vital capacity
FEV1.0
Forced expiratory volume
FER
Forced expiratory ratio
PEFR
Peak expiratory flow rate
Henry’s Law
The quantity of a gas that will dissolve in a liquid is proportional to the partial pressure of the gas
Factors that affect rate of diffusion
V = volume of gas diffusing through membrane A = surface area of respiratory membrane D = diffusion coefficient of the gas T = thickness of membrane P1-P2 = partial pressure difference of the gas across the membrane
V = ( A x D x (P1-P2) ) / T
Partial pressure
pressure of a component of a gas mixture in air
Gas movement
Gas moves from an area of high pressure to an area of low pressure
Hb increases carrying capacity of blood by how much?
70 X
Hb composed of
Iron core
4 Haem groups
each group binds 1 O2
each Hb carries 4 O2
Bohr effect
H+ bind to Hb and alter shape, decreasing affinity for O2
Decreased pH leads to decreased saturation
curve shifts right
CO2 primary cause
2,3 diphosphoglycerate
metabolite of CHO metabolism in RBCs
Acts as inhibitor, binds to Haem
Foetal Hb has poor binding of 2,3 DPG hence greater affinity for O2
Foetal Hb causes curve to shift…
right
Myoglobin
Only binds 1 O2
Higher affinity for O2 so only releases it at very low PO2
What controls breathing?
Medulla and Pons
What fine tunes inspiration ?
Pneumotaxix centre
What fine tunes expiration?
Apneustic centre
Medulla oblongata has 2 centres
Dorsal respiratory group: controls diaphragm and external muscles
Quiet breathing
Ventral respiratory group
Controls accessory inspiratory and expiratory muscles
Forced breathing
Respiratory reflexes brought about by:
Chemoreceptors
Baroreceptors
Central Chemoreceptors
monitor composition of CSF
respond to rude in [H+] and PCO2
stimulation increases depth and rate of respiration
Baroreceptors
Afferent fibres stimulated by a rise in BP
fall in BP = increased ventilation
rise in BP = decreased ventilation
Hering Breuer reflexes
Inflation reflex
overexpansion of lungs stimulates stretch receptors in bronchioles
DRG inhibited, VRG stimulated
Active exhalation
Deflation reflex
stimulated by decreased alveolar vol
VRG inhibited, DRG stimulated
Inhibition of expiration
