Anatomy of the thorax

1. ANATOMY OF THE THORAX 1
By
Dr Nassar Ayoub
Assist. Prof. of Anatomy

2. Muscles of thorax
●Extrinsic muscles
Pectoralis major
Pectoralis minor
Serratus anterior
●Intrinsic muscles
1- External Intercostals
2- Internal Intercostals
3- Innermost Intercostals
4-Transverses thoracis
2

3. External intercostal muscles
 Origin: lower border of riⅡ)
 Insertion: upper border of rib below origin
 Action: elevate ribs adding in forced inspiration
Replaced anteriorly by external intercostals
membrane.
Internal intercostal muscles
Origin: upper border of rib
Insertion: lower border of rib
above origin
 Action: depress ribs for forced expiration
 Replaced posteriorly by internal intercostals
membrane.
3

4. Diaphragm
Shape and position:
dome-shaped between thorax and
abdomen, consists of a peripheral
muscular part and a central
tendon
Origin
 Sternal part: xiphoid process
 Costal part: lower six costal
cartilages
 Lumbar part: arises by two crura
from upper 2-3 lumbar vertebrae
Insertion: central tendon
Weak areas: triangular spaces
without muscular tissue
 Lumbocostal triangle:
between costal and lumbar parts.
 Sternocostal triangle: between
costal and sternal parts.
4

5. Openings in the diaphragm
 Aortic hiatus－ lies anterior to the
body of the 12th thoracic vertebra
between the crura. It transmits the
aorta, thoracic duct
 Esophageal hiatus －for esophagus
and vagus nerves at level of T10.
 Vena cava foramen －for inferior
vena cava, through
central tendon at T8 level

6. Action:
 Contraction: the dome moving downward,
increases the volume of thoracic cavity which
results in inspiration, at the same time the intra-
abdominal pressure is increased assists in
defecation, vomiting or child birth.
 Relaxation: the dome returns to the former
position, reduces the volume to the thoracic
cavity, resulting in expiration.
6

7. Arteries of thorax
Pulmonary trunk
Arises from right ventricle
Runs up, back ,and to the left
Bifurcates inferior to aortic arch into
right and left pulmonary arteries, one
for each lung
Pulmonary arteries
Right pulmonary artery－passes
posterior to ascending aorta and
superior vena cava to hilum of right
lung
Left pulmonary artery－passes
anterior to descending aorta and left
main bronchus to hilum of left lung
7

8. Arterial ligament － remnant of ductus
arteriosus, connects bifurcation of
pulmonary trunk to inferior border of
aortic arch
• Triangule of ductus
arteriosus
• Bounded by phrenic n.,
left vagus n. and left
pulmonary a.
• Contents－ arterial
ligament , left recurrent
n. and superficial
• cardiac plexuses
8

9. Ascending aorta
 Runs upward, forward
and to the right,
 Extends to level of
second right
sternocostal joint
 Branches: right and left
coronary arteries
9

10. Aortic arch
 Continuation of ascending aorta
 Curves upward, to the left and
posteriorly, then downward, arching over
left principal bronchus and pulmonary
trunk to lower border of T4 level, to
become descending aorta
 Branches (from right to left )
 Brachiocephalic trunk－extends to right
sternoclavicular joint, bifurcates into right
subclavian and right common carotid
arteries
 Left common carotid artery
 Left subclavian artery
 Aortic isthmus－baroreceptor
 Aortic glomera－chemoreceptor
10

11. Thoracic aorta
 Continuation of aortic arch at lower border of T4
 Courses downward on left side of, then in front of
vertebral column
 Passes through aortic hiatus of diaphragm at

level of T12 vertebra to enter abdominal cavity
 Main branches
Parietal branches
Nine pairs posterior intercostals arteries
One pair subcostal artery


 For lower nine intercostals spaces and
upper part of abdominal wall; superior
phrenic arteries supply the superior

surface of the diaphragm.
Visceral branches
 Bronchial branches: one or two for each


lung
Esophageal branches
Pericardial branches

12. Internal thoracic artery －
descends into thorax
1.2cm lateral to edge of
sternum, and ends at
the sixth costal cartilage
by dividing
musculophrenic and
superior epigastric
arteries
12

13. Veins of thorax
Brachiocephalic veins
Formed by union of internal jugular and subclavian
veins posterior to the sternoclavicular joint
Angle of union is termed venous angle
Superior vena cava
Formed by union of right and left brachiocephalic veins
behind the right sternocostal synchorndrosis of first rib
Runs vertically down on right of ascending aorta
Joined by azygos vein at level of sternal
angle
Enters right atrium at lever of lower
border of third right sternocostal joint
Collects blood from veins of upper half of body
14

14. Azygos vein
 Begins as continuation of right
ascending lumbar vein
 Ascending along the right side of
vertebral column
 Joins superior vena cava by aching
above right lung root at level of T4 to
T5
 Receives right posterior intercostals
and subcostal veins plus some of
bronchial, esophageal and pericardial
veins, and hemiazygos vein
 Tributaries－hemiazygosv. and
accessory hemiazygos v. which
receive most left posterior
intercostals vein and left bronchial
veins
15

15. Veins of vertebral
column
Consists of
 External vertebral
venous plexus
 Internal vertebral
venous plexus
16

16. Lymph nodes of the thoracic contents
Lymph nodes of trachea,
bronchi and lungs
 Pulmonary lymph nodes lie in
the angles of bifurcation of
branching lobar bronchi
 Bronchopulmonary hilar lymph
nodes－lie in the hilus of the
lung
 Tracheobronchial lymph nodes
－situated above or below the
bifurcation of trachea
 Paratracheal lymph nodes
－along each side of the trachea
18

17. Thoracic duct
Begins in front of L1 as a dilated
sac, the cisterna chyli, which formed
by joining of left and right lumbar
trunks and intestinal trunk
Enter thoracic cavity by passing
through the aortic hiatus of the
diaphragm and ascends along on the
front of the vertebral column,
between thoracic aorta and azygos
vein
Travels upward, veering to the left at
the level of T5
 At the roof of the neck, it turns
laterally and arches forwards and
descends to enter the left venous
angle
20

18.  Just before termination, it receives the
left jugular, subclavian and lymph from
lower limbs, pelvic cavity, abdominal
cavity, left side of thorax, and left side of
the head, neck and left upper limb
Right lymphatic duct
 Formed by union of right jugular,
subclavian, and bronchomediastinal
trunks
 Ends by entering the right venous angle
 Receives lymph from right half of head,
neck, thorax and right upper limb,
bronchomediastinal trunks
21

19. Phrenic nerve
 Descends over scalenus
anterior to enter thorax
 Accompanied by
pericardiophrenic vessels and
passes anterior to lung roots
between mediastinal pleura
and pericardium to supply
motor and sensory
innervation to diaphragm
 Sensory fibers supply to
pleurae, pericardium and
peritoneum of diaphragm;
usually right phrenic nerve
may be distributed on liver,
gallbladder and biliary
system.
25

20. Left vagus nerve
Enter thoracic inlet between left
common carotid and left subclavian
arteries, posterior to left
brachiocephalic vein
 Crosses aortic arch where left
recurrent laryngeal nerve branches
off
 Passes posterior to left lung root
 Forms anterior esophageal plexus
 Forms anterior vagal trunk at
esophageal hiatus where it leaves
thorax and passes into abdominal
cavity , then divides into anterior
gastric and hepatic branches
26

21. Right vagus nerve
 Enter thoracic inlet on right side
of trachea
Travels downward posterior to
right brachiocephalic vein and
superior vena cava
Passes posterior to right lung
root
Forms posterior esophageal
plexus
Forms posterior vagal trunk at
esophageal hiatus where it
leaves thorax and passes into
abdominal cavity, then divides
into posterior gastric and celiac
branches
27

22. 28
Recurrent laryngeal nerves
 Right one hooks around right
subclavian artery, left one hooks
aortic arch
 Both ascend in tracheo-
esophageal groove
 Nerves enter larynx posterior to
cricothyroid joint, the nerve is
now called inferior laryngeal
nerve
 Innervations: laryngeal mucosa
below fissure of glottis , all
laryngeal laryngeal muscles
except cricothyroid
Bronchial and esophageal
branches

23. 29Thoracic sympathetic trunk
 Branches of sympathetic trunk to
thoracic plexuses
 Greater splanchnic nerve
formed by preganglionic fibers from
T5~T9 ganglia, and relay in celiac
ganglion.
 Lesser splanchnic nerveformed by
preganglionic fibers from T10~T12
ganglia, and relay in aorticorenal
ganglion.
 The postganglionic fibers supply the
liver, spleen, kidney and alimentary tract
as far as the left colic flexure.

24. Regional anatomy of
thorax
30

25. Parts and regions of the thorax
Boundaries
 Superior－jugular notch,
sternoclavicular joint, superior border
of clavicle, acromion, spinous
processes of C7
 Inferior－xiphoid process,
costal arch, 12th and 11th ribs,
vertebra T12
Regions
 Thoracic wall
 Thoracic cavity
F
31

26. Landmarks
 Jugular notch corresponds with
 The 2th thoracic vertebra in male, the 3th
thoracic vertebra in female
 Sternal angle connects 2nd costal cartilage
laterally， corresponds with
 The lower border of 4th thoracic vertebra
 The bifurcation of trachea in the adult
 The beginning of aortic arch which ends
posteriorly at the same level
 The esophagus is crossed by the left main
bronchus
32

27. Thoracic wall
 Skin
 Superficial fascia
 Thoracoepigastric v.
 Supraclavicular n.
 Anterior and lateral cutaneous
branches of intercostal n.
 Deep fascia
34

28. Lymphatic drainage of breast
 Into pectoral Ln. from lateral and
central parts of breast
Into apical and supraclavicular Ln.
from superior part of breast
Into parasternal Ln. from medial part
of breast
Into interpectoral Ln. from deep
part of breast
The lymphatic capillaries of breast form
an anastomosing network which is
continuous across the midline with that
of the opposite side and with that of
the abdominal wall
36

29. The Mediastinum
Concept－all of organs between the left
and right mediastinal pleurae is called
mediastinum. It extends from the
sternum in front to the vertebral column
behind, and from the thoracic inlet
above to the diaphragm below.
38

30. Subdivisions of mediastinum
 Superior mediastinum
 Inferior mediastinum
 Anterior mediastinum
 Middle mediastinum
 Posterior mediastinum
39

31. Left side of
mediastnum 40

32. Right side of mediastnum
41

33. Superior mediastinum
Locating－from inlet of thorax
to plane extending from level
of sternal angle anteriorly to
lower border of T4 vertebra
posterioly
Contents
 Superficial layer
 Thymus
 Three veins
Left brachiocephelic v.
Right brachiocephelic v.
Superior vena cava
42

34.  Middle layer
 Aotic arch and its
three branches
 Phrenic n.
 Vagus n.
43

35.  Posterior layer
 Trachea
 Esophagus
 Thoracic duct
44

36. Anterior mediastinum
Anterior mediastinum
 Location－posterior to body of
sternum and attached costal
cartilages, anterior to heart and
pericardium
 Contents－fat, remnants of
thymus gland, anterior mediastinal
lymph nodes
47

37. Middle mediastinum
 Location－between anterior
mediastinum and posterior
mediastinum
 Contents: hart and
pericardium, beginning or
termination of great vessels,
phrenic nerves,
pericardiacophrenic vessels ,
lymph nodes,
48

38. Posterior mediastinum
 Location－posterior to heart
and pericardium, anterior to
vertebrae T5－T12
 Contents: esophagus, vagus
n., thoracic aorta, azygos
system of veins, thoracic duct,
thoracic sympathetic trunk,
posterior mediastinal lymph
nodes
49

39. Mediastinal spaces
 Retrosternal space －lies beween
sternum and endothoracic fascia
Pretracheal space －lies within
superior mediastinum, between
trachea, bifurcation of trachea and
aortic arch
Retroesophagus space － lies
within superior mediastinum,
beween esophagus and
endothoracic fascia
54