Respiratory system functions: Muscles of respiration (all skeletal) Inspiration = active process
- Gaseous exchange Diaphragm: most powerful, biggest Expiration = normally passive
- Acid-base balance (7.4) contributor to tidal volume (1/3 – ½ Air flow determined by pressure
- Phonation around 0.5 L) differences resulting from an
- Pulmonary defence mechanism upstream rise or a downstream
- Pulmonary metabolism Intercostals: between ribs, less fall. Humans = negative pressure
powerful, responsible for rib breathers – downstream fall.
Structure: movement.
Upper respiratory system – pharynx, Inspiration
oral & naval cavities Accessory muscles: mostly neck Cause a -ve pressure in relation
Lower respiratory system – trachea, muscles, only used in extreme to the atmosphere. Inspiratory
bronchi, alveoli distress or in forced expiration muscles contract, diaphragm
(In forced expiration, when it is contracts, ribs up & out, thoracic
Bronchial tree: necessary to empty the lungs of cavity volume increases. Pip
Consists of the trachea and the more air than normal, the abdominal becomes more negative ->
lobar bronchi ( left = 2 lobes – muscles contract and force the increases Ptp, alveolar volume
inferior and superior; right = 3 lobes diaphragm upwards and contraction increases, Palv decreases. Air in.
– inferior, middle & superior), as of the internal intercostal muscles
well as segmental bronchi. Each actively pulls the ribs downwards. Expiration
segment has its own blood supply. the equal pressure point moves Cause a +ve pressure in relation
toward the alveoli and collapsible to the atmosphere. Inspiratory
Tracheal bifurcation – the division of small airways. The lung volume muscles relax, chest recoils, Pip
the trachea into the right and left decreases, leading to smaller alveoli becomes less negative, decreases
main bronchi at the level of the with less alveolar elastic recoil. Ptp, alveolar volume decreases,
sternal angle/angle of Louis/ carina. Palv increases. Air out.
Airways: conduction zone =
Anatomy and
Alveolar interdependence
generations 1-16. Gets air from one
point to another
physiology of the The pulling of the parietal pleura
pulls on the visceral pleura,
Respiratory zone = generations 17- lungs which then pulls on the outer
alveoli. This then affects the next
23. Focused on gas exchange Pleura alveoli and so on, due to the
The parietal pleura continues alveoli being physically
Work of breathing
beyond the lungs down to the connected (connective tissue).
1) Resistance: the resistance of the
diaphragm (12th rib). Space This also prevents alveoli
respiratory tract to airflow during
between the pleura layers (costal collapsing as they are supported
inspiration & expiration.
& mediastinal) = by surrounding alveoli. This is
Poiseuille’s law. Predominantly
costodiaphragmatic recess. also aided by a surfactant
an expiration issue, affected by
Pathophysiology can cause excess (lipoprotein of type II alveolar
the diameter of airways
fluid to collect here. cells) which lowers surface
2) Compliance/distensibility :
Cervical pleura extend for 2.5 cm tension (reduced H20 attraction
measure of the lung’s ability to
above the clavical/collarbone. between alveoli). This increases
stretch and expand (note
difference to elasticity) compliance.
Resistance Vs compliance. Pneumothorax- shows Pip
Resistance increase = obstructive importance. When seal broken
disease. Airway narrowing, e.g. parietal & visceral pleura
asthma, -> increases respiratory rate. separate -> elastic recoil of
Children are at a greater risk as they alveoli.
have smaller airways & higher
respiratory rates
Compliance increase = restrictive
disease. Increases thickness of tissue.
Low compliance = very thick tissue.
(fibrosis).High compliance = very thin
tissue -> rupture (emphysema)
