2. The trachea is a tube formed of cartilage
and fibromuscular membrane, lined
internally by mucosa.
The anterolateral portion is made up of
incomplete rings of cartilage, and the
posterior aspect by a flat muscular wall. It
is C shaped.10-11 cm long, and descends
from the larynx.
5. from the level of the sixth cervical
vertebra to the upper border of the fifth
thoracic vertebra, where it divides into
right and left principal (pulmonary)
bronchi.
It lies approximately in the sagittal plane,
but its point of bifurcation is usually a little
to the right.
6.
7.
8. The trachea is mobile and can rapidly alter
in length: thus, during deep inspiration, the
bifurcation may descend to the level of the
sixth thoracic vertebra .
Its external transverse diameter is c.2 cm
in adult males, and 1.5 cm in adult
females.
In children it is smaller, more deeply
placed and more mobile.
9. The lumen in live adults is c.12 mm in
transverse diameter, although this
increases after death as the smooth
muscle making up its posterior aspect
relaxes.
In the first postnatal year, the tracheal
diameter does not exceed 4 mm, while
during later childhood its diameter in
millimetres is approximately equal to age
in years.
10. The transverse shape of the lumen is
variable, especially in the later decades of
life, and may be round, lunate or
flattened.
At bronchoscopy the posterior wall of the
trachea bulges into the lumen and this is
exaggerated in expiration and coughing.
11. The distal end of the trachea is visible as a
concave spur.
A tracheal bronchus may occasionally
arise from the lateral wall of the trachea,
more frequently from the right side:
it may be supernumerary or it may
represent a displaced upper lobe airway.
12.
13.
14.
15. Cervical part of the trachea:
Anterior relations.
The cervical trachea is crossed anteriorly
by skin and by the superficial and deep
cervical fasciae.
It is also crossed by the jugular arch and
overlapped by sternohyoid and
sternothyroid.
16. The second to fourth tracheal cartilages
are crossed by the isthmus of the thyroid
gland, above which an anastomotic artery
connects the bilateral superior thyroid
arteries;
below this and in front are the pretracheal
fascia, inferior thyroid veins, thymic
remnants and the thyroid ima artery.
17. In children the brachiocephalic artery
crosses obliquely in front of the trachea at,
or a little above;
the upper border of the manubrium; the
left brachiocephalic vein may also rise a
little above this level.
18. Behind the cervical trachea is the
oesophagus, which runs between the
trachea and the vertebral column.
The recurrent laryngeal nerves ascend
on each side, in or near the grooves
between the sides of the trachea and
oesophagus.
19. The lateral relations of the trachea are the
paired lobes of the thyroid gland,
which descend to the fifth or sixth
tracheal cartilage, and the common
carotid and inferior thyroid arteries.
20. Anterior relations :
As it descends through the superior
mediastinum, the thoracic trachea lies
behind the manubrium of sternum;
the attachments of sternohyoid and
sternothyroid, the thymic remnants and
the inferior thyroid vein.
21. The brachiocephalic and left common
carotid arteries come to lie on the right
and left respectively of the trachea as they
diverge upwards into the neck.
At a lower level the aortic arch, the
brachiocephalic and left common
carotid arteries, left brachiocephalic
veins, deep cardiac plexus and some
lymph nodes are all anterior to the
trachea.
22.
23. The oesophagus is posterior to the
trachea and separates it from the vertebral
column.
24. Laterally and on the right are the right lung
and pleura, right brachiocephalic vein,
superior vena cava, right vagus nerve
and azygos vein.
On the left are the arch of the aorta, left
common carotid and left subclavian
arteries.
25. The left recurrent laryngeal nerve is at
first situated between the trachea and
aortic arch, and then lies in, or just in front
of, the groove between the trachea and the
oesophagus.
26. Trachea splits into a left &
right primary bronchus which
enters into the hilus of each
lung
Within the lung, the primary
bronchi branch into secondary
(lobar) bronchi (3 in right lung/2
in left lung)
Secondary bronchi then
branch into 10 tertiary
(segmental) bronchi
Tertiary bronchi then continue
to branch into smaller &
smaller bronchi & then into
very narrow bronchioles
27.
28. The right principal bronchus is wider,
shorter and more vertical than the left,
being c.2.5 cm long:
this explains why inhaled foreign bodies
enter it more often than the left.
These events are more common in
children and they may present with
breathlessness, unilateral wheeze or
recurrent aspirations.
29. A chest radiograph may show air trapping
in the affected lobe.
The right main bronchus gives rise to its
first branch, the superior lobar bronchus,
then enters the right lung opposite the fifth
thoracic vertebra.
The azygos vein arches over it and the
right pulmonary artery lies at first
inferior, then anterior, to it.
30. After giving off the superior lobar bronchus,
which arises posterosuperior to the right
pulmonary artery;
the right main bronchus crosses the
posterior aspect of the artery, enters the
pulmonary hilum posteroinferior to it,
and divides into a middle and an inferior
lobar bronchus.
31. Normal variants in the bronchial anatomy
are occasionally seen and consist of either
displaced or supernumerary airways.
Abnormalities include a common origin of
right upper lobe and right middle lobe;
an accessory cardiac bronchus; and a
right lower lobe bronchus that may arise
from the left main stem bronchus.
32.
33. These anatomic variants are largely
asymptomatic, but occasionally may cause
haemoptysis, recurrent infection and
development of bronchiectasis of the
airway.
34. There are 10 bronchopulmonary segments
in the right lung divided into the 3 lobes:
36. The right superior lobar bronchus arises
from the lateral aspect of the parent
bronchus and runs superolaterally to enter
the hilum; c.1 cm from its origin it divides
into three segmental bronchi.
37. The apical segmental bronchus continues
superolaterally towards the apex of the
lung, which it supplies, and divides near its
origin into apical and anterior branches.
The posterior segmental bronchus serves
the posteroinferior part of the superior
lobe, passes posterolaterally and slightly
superiorly and soon divides into a lateral
and a posterior branch.
38. The anterior segmental bronchus runs
anteroinferiorly to supply the rest of the
superior lobe, and divides near its origin
into a lateral and an anterior branch of
equal size
39. The right middle lobar bronchus starts c.2 cm
below the superior lobar bronchus, from the
front of right bronchus intermedius and
descends anterolaterally.
Segmental anatomy
The right middle lobar bronchus soon divides
into a lateral and a medial segmental
bronchus: these pass to the lateral and
medial parts of the middle lobe, respectively.
40. The right inferior lobar bronchus is the
continuation of the principal bronchus
beyond the origin of the middle lobar
bronchus. Segmental anatomy
41. The right inferior lobar bronchus gives off a
large superior (apical) segmental
bronchus posteriorly. This runs posteriorly
to the upper part of the inferior lobe, and
then divides into medial, superior and
lateral branches:
42. the first two usually arise from a common
stem. After giving off the superior
segmental branch, the right inferior lobar
bronchus descends posterolaterally.
The medial basal segmental bronchus
branches from its anteromedial aspect,
and runs inferomedially to serve a small
region below the hilum.
43. The left principal bronchus, which is
narrower and less vertical than the
right, is c.5 cm long, and enters the hilum
of the left lung at the level of the sixth
thoracic vertebra.
Passing to the left inferior to the aortic
arch, it crosses anterior to the
oesophagus, thoracic duct and
descending aorta.
44. The left pulmonary artery is at first
anterior and then superior to it. After it
enters the hilum, it divides into a superior
and an inferior lobar bronchus.
45. The left superior lobar bronchus arises
from the anterolateral aspect of its parent
stem, curves laterally and soon divides into
two bronchi which correspond to the
branches of the right principal bronchus as
it supplies the right superior and middle
lobes
46. However, on the left side both are
distributed to the left superior lobe
because there is no separate middle lobe.
48. The superior division of the left superior
lobar bronchus ascends c.1 cm, gives off
an anterior segmental bronchus, continues
a further 1 cm as the apicoposterior
segmental bronchus and then divides into
apical and posterior branches.
49. The apical, posterior and anterior
segmental bronchi are largely distributed
as they are in the right superior lobe.
The inferior division descends
anterolaterally to the anteroinferior part of
the left superior lobe (the lingula) and
forms the lingular bronchus, which
divides into superior and inferior lingular
segmental bronchi.
50. The left inferior bronchus descends
posterolaterally and divides to supply
territories of the lung that are distributed in
essentially the same manner as they are in
the right lung.
51. The superior (apical) segmental bronchus
arises from the inferior lobar bronchus
posteriorly c.1 cm from its origin. After a
further 1-2 cm, the inferior lobar bronchus
divides into an anteromedial and a
posterolateral stem.
52. The latter divides into lateral and
posterior basal segmental bronchi.
The anterior basal segmental bronchus
is an independent branch of the inferior
lobar bronchus in c.10% of lungs.
A subsuperior (subapical) segmental
bronchus arises posteriorly from the left
inferior lobar bronchus in 30% of lungs
53. The trachea is supplied with blood mainly
by branches of the inferior thyroid
arteries.
The bronchial arteries, whose branches
ascend to anastomose with the tracheal
branches of the inferior thyroid arteries,
also supply its thoracic portion.
54. Veins draining the trachea end in the
inferior thyroid venous plexus. The lymph
vessels pass to the pretracheal and
paratracheal lymph nodes.
55. The bronchial arteries supply oxygenated
blood to maintain the pulmonary tissues.
They are derived from the descending
thoracic aorta either directly or indirectly .
The right bronchial artery is usually a branch
of the third posterior intercostal artery, whilst
there are normally two left bronchial arteries
(upper and lower) that branch separately from
the thoracic aorta.
56. The bronchial arteries accompany the
bronchial tree and supply bronchial glands,
the walls of the bronchial tubes and larger
pulmonary vessels.
The bronchial branches form a capillary
plexus in the muscular tunic of the air
passages, and this supports a second,
mucosal plexus, which communicates with
branches of the pulmonary artery and
drains into the pulmonary veins.
57. The bronchial veins form two distinct
systems. Deep bronchial veins commence
as intrapulmonary bronchiolar plexuses
that communicate freely with the
pulmonary veins and eventually join a
single trunk that ends in a main pulmonary
vein or in the left atrium.
58. Superficial bronchial veins drain
extrapulmonary bronchi, visceral pleura
and the hilar lymph nodes.
They also communicate with the
pulmonary veins and end in the azygos
vein on the right and in the left superior
intercostal or the accessory hemiazygos
veins on the left.
59. The deep lymphatic plexus reaches the
hilum by travelling along the pulmonary
vessels and bronchi.
In larger bronchi the deep plexus has
submucosal and peribronchial parts, but in
smaller bronchi there is only a single
plexus that extends to the bronchioles.
The walls of the alveoli have no lymphatic
vessels.
60. The anterior and posterior pulmonary
plexuses innervate the trachea and the
bronchi
The two plexuses are interconnected.
The nerves enter the lung as networks
that travel along branches of the bronchi
and pulmonary and bronchial vessels as
far as the visceral pleura.
61. The trachea is innervated by branches of
the vagi, recurrent laryngeal nerves and
sympathetic trunks, distributed to the
tracheal smooth muscle, mucosal glands
and blood vessels. Efferent vagal
preganglionic axons synapse on small
ganglia within the walls of the
tracheobronchial tree:
62. Bronchoscopy allows the direct
visualization of the vocal cords, trachea
and major airways as far as the first
division of the subsegmental airway .
