TRACHEA

1. ANATOMY OF TRACHEA &
BRONCHI
Dr. Ramya. C
PG 1st year
Department of ENT

2. THE TRACHEA
 A cartilaginous and membranous tube , 11 cm in length.
 Extends from the lower border of cricoid cartilage to the
carina, where it bifurcates into the left and right main bronchi.
 Bifurcation is at the level of T5 posteriorly and the
manubriosternal angle anteriorly.
 Moves upwards during swallowing and down and forwards
during inspiration.
 D-shaped in cross-section with incomplete cartilaginous rings
anteriorly & laterally and a straight mucous membrane
posteriorly.
 In children, the trachea is smaller and more mobile than in the
adult and the bifurcation is higher until the age of 10-12 years.

4. RIGHT MAIN BRONCHUS & IT’S
BRANCHES
• 5 cm long and extends to its division into the right middle and
lower lobe bronchus.
• Wider, shorter and more vertical, making an angle of 25-30°
with the carina.
More likely that food, fluid & foreign bodies aspirated into the
airway will enter this side.
• Diameter: 17mm (±4mm) in men
15mm (±4mm) in women
• Right pulmonary artery is at first below and in front of it.
• Azygos vein arches over it.

6. LEFT MAIN BRONCHUS & IT’S
BRANCHES
• Extends from carina to its division into the upper and
lower lobe bronchi.
• Narrower than the right main bronchus & more horizontal,
making an angle of 45° with the trachea.
• Extends laterally beneath the aortic arch and crosses
anterior to the oesophagus, thoracic duct and descending
aorta.
• Left pulmonary artery lies first anterior then superior to it.
• Enters the hilum and divides into an upper and lower lobe
bronchus at the level of T6.

7. THE LUNG
• Divided functionally into a series of
bronchopulmonary segments, each with its own
bronchus and its own blood supply from the
pulmonary artery.
• Each segment is surrounded by connective tissue
continuous with that of visceral pleura and
forms a separate respiratory unit of lung.

8. STRUCTURE OF TRACHEA & BRONCHI
• Consists of a framework of incomplete rings
of hyaline cartilage united by fibrous
tissue and nonstriated muscle.
• Lined by mucous membrane.

9. The Cartilages:
• Incomplete rings which stiffen the wall anteriorly and laterally.
• Tube is flat & deficient behind, and is completed by fibrous & elastic tissue
and nonstriated muscle.
• 4 mm high and 1 mm thick.
• They are highly elastic, but may become calcified with age.
• In extrapulmonary bronchi, they are shorter, narrower and less regular, but
similarly arranged.
• The 1st tracheal cartilage is broader than the rest & is sometimes joined with
the cricoid cartilage through the cricotracheal ligament.
• The last tracheal ring is thick and broad in the middle and its lower border
is prolonged into a triangular process which curves downwards and
backwards between the two bronchi forming a bridge which underlies the
carina.

10. The Fibrous Membrane:
• Each of the cartilages is enclosed in perichondrium.
• Fibrous layer of the perichondrium and fibrous membrane are composed mainly of
collagen intermingled with some elastic fibres.
• Fibres cross each other diagonally allowing a change in diameter.
• Elastic component provides elastic recoil when the membrane is stretched.
• Non-striated muscle fibres present at the back are transverse and are inserted into the
perichondrium of posterior extremities of the cartilage.
• They constitute the trachealis muscle which on contraction reduces the cross-section of
the trachea & bronchi.
• Few longitudinal muscle fibres lie external to the transverse fibres.
• The relative thickness of the muscle increases as the branching bronchi become narrower.
• The outer fibrous and muscular layers of the continuous with the fascial planes of the
surrounding muscle and the oesophagus and with the loose areolar tissue of the
mediastinum.

12. The Mucous Membrane:
• Pseudostratified, ciliated, columnar epithelium with numerous goblet cells resting on
a broad basement membrane.
• Deep to the epithelium & basement membrane is lamina propria, rich in longitudinal
elastic fibres.
• Next is submucosa of loose irregular connective tissue in which are situated larger
blood vessels, nerve trunks and most of the tubular glands and lymphoid patches.
• Deep to the submucosa is the perichondrium and fibrous layer.

13. NERVE SUPPLY
• The muscle fibres of the trachea including the trachealis are
innervated by the recurrent laryngeal nerves which also carry
sensory fibres from the mucous membrane.
• The lungs: Anterior and posterior pulmonary plexuses
situated at the hilum of each lung.
• Efferent sympathetic fibres are post-ganglionic branches of
2nd- 5th thoracic ganglion with an occasional contribution from
stellate ganglion- dilators to bronchi & pulmonary arterioles.
• Parasympathetic fibres to the trachea and bronchi are carried
in the vagus nerve- efferents are bronchoconstrictor to the
bronchial muscles and secretomotor & vasodilator to the
bronchial mucous glands- afferents are involved in cough
reflex.

15. BLOOD SUPPLY
• Trachea is supplied by the superior and inferior
thyroid arteries.
• Thoracic part & bronchi to the respiratory
bronchioles are supplied by the bronchial arteries.
• Left bronchial artery- paired- arise from descending
thoracic aorta.
• Right bronchial artery- single- may arise from the
aorta/ 1st intercostal artery/ 3rd intercostal artery/
internal mammary/ right subclavian artery.

16. Contd… Venous Drainage
• Tracheal veins drain upwards to the thyroid venous
plexus.
• Deep bronchial veins commence as a network in the
intrapulmonary bronchioles  pulmonary veins 
form a single trunk  terminates in main
pulmonary vein / in left atrium.
• Superficial bronchial veins drain the
extrapulmonary bronchi, the visceral pleura & hilar
lymph nodes  terminate in the azygos vein on
right side & left superior intercostal vein / accessory
hemiazygos vein on left side.

17. LYMPHATIC DRAINAGE
• Lymphatics arise in a plexus beneath mucous membrane &
penetrate muscular coat to form a plexus in the outer fibrous
membrane.
• Lymphatics from the smaller bronchi  pulmonary nodes
around the airway  join lymphatics from large bronchi 
bronchopulmonary nodes beneath the points of division of
intrapulmonary airways.
• Lymphatics from trachea  pretracheal and paratracheal
group.
• Lymphatics from right and left paratracheal nodes unite with
vessels from internal thoracic and brachiocephalic lymph
nodes  form the right and left bronchomediastinal trunks 
right lymphatic duct & left thoracic ducts / independently
into junction of internal jugular vein and subclavian veins.

18. RELATIONS OF TRACHEOBRONCHIAL
TREE
• Anteriorly - skin, superficial & deep fascia and by sternohyoid and
sternothyroid muscles in lower part of the neck.
• 2nd to 4th tracheal rings- Isthmus of thyroid.
• Lower in the neck and superior mediastinum - inferior thyroid
veins, thyroid ima artery (when present) & thymus gland.
• Lower in the mediastinum - left brachiocephalic vein, arch of aorta,
brachiocephalic and left common carotid arteries, deep part of the
cardiac plexus and pretracheal & paratracheal lymph nodes.
• The left brachiocephalic vein may project upwards into the neck to
form an anterior relation of cervical trachea - potential surgical
hazard during tracheostomy.

19. • Axial section at C7 showing
relationship of upper trachea
to surrounding structures. 1.
Sternohyoid muscle; 2.
sternothyroid muscle; 3.
sternocleidomastoid muscle;
4. thyroid gland; 5. left vagus
nerve; 6. cervical sympathetic
ganglion; 7. left recurrent
laryngeal nerve; 8.
oesophagus; 9. inferior thyroid
artery; 10. common carotid
artery; 11. internal jugular
vein; 12. trachea.

20. Contd…
• Laterally, right and left lobes of the thyroid
gland which descend to the level of the 5th & 6th
tracheal cartilages lie on either side of trachea,
carotid sheath enclosing common carotid artery,
internal jugular vein and vagus nerve.
• Posteriorly, oesophagus - in the groove
between them is recurrent laryngeal nerve.

21. • Axial section at T4 showing
the 12 relationship of the
thoracic trachea to
surrounding structures. 1.
Second costal cartilage; 2.
aortic arch; 3. left vagus nerve;
4. left recurrent laryngeal
nerve; 5. thoracic duct; 6. 4th
thoracic vertebra; 7. superior
vena cava; 8. right phrenic
nerve; 9. tracheal bifurcation;
10. azygos vein; 11. right vagus
nerve; 12. oesophagus