This document summarizes the muscles, arteries, veins, nerves and other structures of the thorax. It describes the intrinsic and extrinsic muscles of the thorax including the intercostal muscles and diaphragm. It details the major arteries and veins of the thorax such as the pulmonary trunk, aorta, superior vena cava and azygos vein. It also outlines the lymphatic drainage and innervation of the thorax including the phrenic, vagus and recurrent laryngeal nerves. Finally, it provides an overview of the regions and landmarks of the thorax including the mediastinum.

1. Thorax
MUHAMMAD RAMZAN UL REHMAN
1

2. The muscles of thorax
Extrinsic muscles
 Pectoralis major
 Pectoralis minor
 Serratus anterior
Intrinsic muscles
 Intercostales externi
 Intercostales interni
 Intercostales intimi
 Transverses thoracis
2

3. Intercostales externi
 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.
Intercostales interni
 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 and 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
5
T8
T10
T12

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
11

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. 13

14. 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

15. 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

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

17. The lymphatic drainage of thorax
The lymphatic drainage of thoracic
wall
 To axillary lymph nodes
 To parasternal lymph
nodes (along internal
thoracic vessels)
 To intercostals lymph
nodes from deeper
structures
17

18. 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

19.  Anterior mediastinal
lymph node lies anterior
to the large blood vessels of
thoracic cavity and
pericardium; the efferents
unite with those of
paratracheal lymph nodes,
to form the right and left
bronchomediastinal trunks .
The left bronchomediastinal
trunk terminates in thoracic
duct, and right in the right
lymphtic duct
 Posterior mediastinal
lymph nodes lie along
the esophagus and thoracic
aorta
19

20. 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

21.  Just before termination, it receives
the left jugular, subclavian and
bronchomediastinal trunks
 Drains 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
21

22. Anterior branches of thoracic nerves
 Intercostal nerves (anterior rami of
T1- T11): runs forward inferiorly to
intercostals vessels in costal groove
of corresponding rib, between
intercostals externi and intercostals
interni; first six nerves are distributed
within their intercostals space,
lower five intercostals nerves leave
anterior ends of their intercostals
spaces to enter abdominal wall
 Subcostal nerve (anterior ramus of
T12): follows inferior border of T12
rib and passes into abdominal wall
 Distribution: distributed to
intercostales and anterolateral
abdominal muscles, skin of
thoracic and abdominal wall,
parietal pleura and peritoneum
22

23. The segmental innervation of anterior surface of
trunk
 T2－sternal angle
 T4－ nipple
 T6－xiphoid process
 T8－costal arch
 T10－umbilicus
 T12－midpoint between umbilicus
and symphysis pubis
23

24. 24

25. 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 live,
gallbladder and biliary
system.
25

26. 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

27. 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

28. 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

29. 29 Thoracic 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 nerve formed 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.

30. Regional anatomy of
thorax
30

31. 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
31

32. 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

33.  Xiphoid process－phisternal
junction lies
opposite the body of the
9th thoracic vertebra
 Clavicle
 Inferior fossa of clavicle
 Coracoid process
 Ribs and intercostal
spaces
 Costal arch
 Infrasternal angle
 Xiphocostal angle
 Papillae
33

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

35. Intercostal space
35
Posterior intercostal v.
Posterior intercostal a.
Intercostal n.

36. 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

37. Internal thoracic vessels
 Internal thoracic a.&v.
 Parasternal ln.
Endothoracic fascia
37

38. 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

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

40. Left side of mediastnum 40
Left vagus n.
Left subclavian a.
Thoracic duct
Aortic arch
Left recurrent n. Thoracic aorta
Phrenic n. &
pericardiacophrenic a.
Root of lung
Pericardium
Sympathetic trunk
Greater splanchnic n
Esophagus

41. Right side of mediastnum 41
Superior vena cava
Phrenic n. &
pericardiacophrenic a.
Root of lung
Pericardium
Trachea
Left vagus n.
Arch of azygos v.
Azygos v.
Sympathetic trunk
Esophagus
Inferior vena cava

42. 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

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

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

45. Relations of aortic arch
 Anteriorly and to the left －
pleura, lung，phrenic n.,
pericardiacophrenic vessels
and vagus n.
 Posteriorly and to the right－trachea,
esophagus, left
recurrent n., thoracic duct,
deep cardiac plexus
 Superiorly－its three branches,
left brachiocephalic v. and
thymus
 Inferiorly－pulmonary a.,
arterial ligament, left recurrent
n., left principal bronchus and
superficial cardiac plexus
45

46. 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
46

47. Inferior 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

48. 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

49. 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

50. Relations of esophagus
 Anteriorly－trachea,
bifurcation of trachea, left
principal branchus, left
recurrent n., right
pulmonary a., anterior
esophageal plexus,
pericardium, left atrium,
diaphragm
50

51.  Posteriorly－posterior
esophageal plexus, thoracic
aorta, thoracic duct, azygos
v., hemiazygos v.,accessory
hemiazygos v., right posterior
intercostal v.
51

52.  Left－left common carotid a., left subclavian a., aortic
arch, thoracic aorta, superior part of thoracic duct
 Right－arch of azygos v.
52

53. Relations of thoracic aorta
 Anteriorly－left root of lung,
pericardium and esophagus
 Posterior－ hemiazygos v.,
accessory hemiazygos v.,
 Right－azygos v. and thoracic
duct
 Left－mediastinal pleura
53

54. 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