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Respiratory tree

Created: 10/9/2010
Updated: 6/8/2021
• C6 – T4
• 10cm long
• D shaped in cross section, reinforced anteriorly by C shaped cartilages
• Bifurcates at T4 to main Bronchi


☼ Relations of trachea (MCQ knowledge, SAQ diagram for e.g. Perc Trache)
• Anterior relations
o Skin, thyroid isthmus at 2nd – 4th tracheal rings
o Jugular arch with anterior jugular vein
o Strap muscles
o Manubrium and remnants of the thymus
o Inferior thyroid veins with brachiocephalic artery
• Lateral relations
o Carotid sheath and RLN in tracheooesophageal groove
o Right lung and pleura
o Brachiocephalic artery
o Azygous veins
o Posterior
o Oesophagus


• Nerve supply to the bronchial tree
o Cardiac plexus around the bifurcation of the trachea
 SNS T2 – T4 contributions
 PNS Vagus (

• Trefoil central tendon
☼ Anteriorly arises from 6 lowest ribs and attached to sternum
• Strong muscular attachments peripherally
☼ Crura (big muscular slings) from L1/2/3 on right and L1/2 on Left
o Left crus forms a loop around the oesophagus to for the lower oesophageal sphincter at T10
☼ Right phrenic and IVC passes through at T8 (no muscle therefore vein not squashed)
☼ T1O=Oesophagus with 2 x vagi applied to its surface providing peristalsis
☼ Aorta, thoracic duct and azygous vein through at T12


• ~T5
• Right= 3cm long and vertical cw
• Left= 5 cm long and horizontal over the heart
• In children these angles are equal so technically a foreign body can go either way

☼ Motor and sensory innervation via phrenic nerves C3/4/5 keeps the diaphragm alive
• Moves < 2cm on quiet breathing
• Moves 10 cm on forced inspiration

☼ Spinal cord injuries at C2/3  respiratory tertaplegia
☼ < C4 25% loss in vital capacity

Blood supply to thorax
• Pulmonary arteries and veins
• Bronchial arteries from the aorta and intercostals supply the bronchi
o Part of the true physiological shunt together with Thebseian veins of the heart



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