The document provides information on the anatomy of the thoracic wall and diaphragm. It discusses the following key points: 1. The thoracic wall is formed by bones including the ribs, sternum, and thoracic vertebrae. It is covered by muscles and fascia externally and pleura internally. 2. The 12 pairs of ribs are connected to the sternum by costal cartilages. There are three types of ribs. 3. The diaphragm is a double-domed muscle that separates the thoracic and abdominal cavities. It has openings for structures to pass through. 4. During inspiration, contraction of the diaphragm and external inter

1. JIGJIGA UNIVERSITY
ANATOMY OF thoracic wall
and diaphragm
FOR MEDICINE STUDENTS
1

2. Introduction
• Thorax is the superior part of trunk between
neck and abdomen
• Contains heart and great vessels, lungs,
thymus, trachea and esophagus
2

3. 3
Structure of the Thoracic Wall
The thoracic wall is covered on the outside by skin and
by muscles attaching the shoulder girdle to the trunk.
The thoracic wall is formed:
 Posteriorly by the thoracic part of the vertebral
column
 Anteriorly by the sternum and costal cartilages
 Laterally by the ribs and intercostal spaces
 Superiorly by the suprapleural membrane; and
 Inferiorly by the diaphragm, which separates the
thoracic cavity from the abdominal cavity

4. Skeleton of
thorax
• Forms:
osteocartilaginous
thoracic cage
• Includes:
12 pairs of ribs
and costal
cartilages
12 thoracic
vertebrae and
intervertebral
discs
Sternum
4

5. 5

6. Ribs
• The ribs are curved, flat bones that form most of the
thoracic cage .
• They are remarkably light in weight yet highly
resilient.
6

7. Ribs cont…
• There are three types of ribs:
1. True (vertebrocostal) ribs (1st- 7th ribs) attach directly
to the sternum through their own costal cartilages.
2. False (vertebrochondral) ribs (8th -10th ) ribs) have
cartilages that are joined to the rib just superior to them;
thus, their connection with the sternum is indirect.
3. Floating (free) ribs (11th- 12th ribs) have rudimentary
cartilages that do not connect even indirectly with the
sternum. 7

8. The ribs have a:
Head: has two facets for articulation with the body of
vertebra.
Neck: is a constricted portion situated between the head
and the tubercle.
Tubercle: located at the junction of neck with shaft.
• It has a facet for articulation with the transverse
process of the numerically corresponding vertebra
8
Ribs cont…

9. Body (shaft): is thin and flattened and twisted on its
long axis.
• Has the costal groove that protects the intercostal
nerve and vessels.
Angle: is where the shaft of the rib bends sharply
forward.
9
Ribs cont…

10. 10

11. 11

12. Costal cartilages
• Connect the upper seven ribs to the lateral edge of the
sternum and the 8th, 9th, and 10th ribs to the cartilage
immediately above (7th).
• The costal cartilages contribute significantly to the
elasticity and mobility of the thoracic walls.
• In old age, the costal cartilages tend to lose some of
their flexibility as the result of superficial calcification.
12

13. Intercostal spaces
• Separate the ribs and their costal cartilages from one
another.
• Spaces and neurovascular structures are named
according to the rib forming the superior border of the
space.
• There are 11 intercostal spaces and 11 intercostal
nerves.
• The subcostal space is below the 12th rib and the
anterior ramus of spinal nerve T12 is the subcostal
nerve.
13

14. Rib Fractures
• The middle ribs are most commonly fractured.
• Rib fractures usually result from blows or crushing
injuries.
• Its broken end may injure internal organs such as a
heart, lung and the spleen.
• Rib fractures are painful because the broken parts
move during respiration, coughing, laughing, and
sneezing.
14

15. The Sternum
• Flat bone
• Lies in the anterior midline of the thorax
• It consists of three fused bones
Manubrium
Body
Xiphoid process
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16. 16

17. Manubrium of the Sternum
• Located at level T3-T4, most widest & thickest
• Superior surface is indented by jugular notch
(superasternal notch)
• Clavicular notch articulate with clavicle
• First rib articulate with lateral margin
• Inferior border articulate with body; forms projection
– sternal angle
17

18. Strenal angle (angle of luois)
• Lies at level of T4 & T5 Intervertebral disc
• Marks level of 2nd pair of costal cartilage at
manubrosternal joint.
• Trachea bifurcates into the main (primary) bronchi at
this angle.
• Arch of aorta give 3 branch at this angle and
• Thoracic aorta begin at level of sternal angle.
18

19. • Located at level of T5-T9
• Approximately 10 cm long;
• Lateral wall has costal notches
Xiphoid process
• Cartilaginous at birth
• Lies in a slight depression, epigastric fossa.
• Lies at the level of T10 vertebra.
19
Body of the Sternum

20. Xiphoid process cont…
• The costal margins form infrasternal (sub costal)
angle
• This angle is used in cardiopulmonary resuscitation
(CPR) for locating proper hand position on inferior
part of sternal body
20

21. 21

22. Sternal Fractures
• Sternal fractures are not common.
• Crush injuries can occur in automobile accidents.
• Use of air bags in vehicles has reduced the number of
sternal fractures.
• The most common site of sternal fracture is at the
sternal angle.
• The concern in sternal injuries is the likelihood of
heart injury (cardiac rupture, tamponade) or lung
injury.
22

23. Thoracic Vertebrae
• There are twelve thoracic vertebrae
• Each of which is characterized by articulations with
ribs.
The special features of these vertebrae are:
1. They have bilateral costal facet (demifacets) on their
bodies for articulation with the heads of ribs
2. They have facets on their transverse processes for
articulation with the tubercles of ribs.
3. They have long spinous processes.
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24. Other important features of thoracic vertebrae
are the following:
• Their bodies are shorter ventrally than dorsally
• Their articular processes are more or less
vertical.
• The spinous process are curved downward
• They contain circular vertebral foramina
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26. 26

27. Thoracic Apertures
Superior thoracic aperture
Also called the anatomical thoracic inlet.
The superior thoracic aperture is bounded:
Posteriorly by the T1 vertebra
Laterally by the first pair of ribs and their costal
cartilages
Anteriorly by the superior border of the
manubrium
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28. 28

29. Inferior thoracic aperture
Also called the anatomical thoracic outlet.
The inferior thoracic aperture is bounded:
Posteriorly by the T12 vertebra.
Posterolaterally by the11th and 12th pairs of ribs.
Anterolaterally by the joined costal cartilages of
ribs 7th -10th , forming the costal margin.
Anteriorly by the xiphisternal joint.
29

30. Imaginary Lines: facilitate anatomical & clinical
description of the body
Anterior median (midsternal) line (AML) –
• Indicates intersection of the median plane with
the anterior thoracic wall.
Posterior median line (PML) – a vertical line
along tips of spinous process of the vertebrae.
Mid clavicualr line (MCL) –
• Passes thru mid point of clavicle, parallel to the
AML.
30

31. Anterior axillary line (AAL)
• Runs vertically along anterior axillary fold that is
formed by inferolateral border of pectoralis major.
Mid axillary line (MAL) – runs from apex (deepest
part) of axillary fossa, parallel to AAL.
Posterior axillary line (PAL) –runs vertically along
posterior axillary fold that is formed by latissimus
dorsi & teres major.
31

32. Muscles of the thoracic wall
• Serratus posterior
– Serratus posterior superior: elevates superior ribs
– Serratus posterior inferior: depress inferior ribs
• Levator costarum: elevates the ribs
• Transversus thoracic: Weakly depress the ribs
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33. 33

34. Muscles of the thoracic wall cont…
• Intercostals
– External intercostal muscles: pulls ribs upward
during inspiration
– Internal intercostal muscles: draws ribs together;
aids in expiration
– Innermost intercostal muscles: the same action
with internal intercostal muscles
• Subcostals: the same action with internal intercostal
muscles
34

35. 35

36. Fascia of Thoracic Wall
• The thoracic cage is lined internally with
endothoracic fascia.
• It attaches the costal parietal pleura to the
thoracic wall.
• It becomes more fibrous over the apex of the
lungs (suprapleural membrane).
36

37. Diaphragm
• The diaphragm is a double-dome shaped, musculo-
tendinous partition separating the thoracic and
abdominal cavities.
• It have convex superior surface, and concave inferior
surface.
• Principal muscle of inspiration
• Composed of two portions:
Muscular (peripheral part)
Aponeurotic (central part)
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38. 38

39. Major openings
Aortic hiatus – at the level of T12, in muscular part
Transmits descending aorta, thoracic duct, azygos vein
Esophageal hiatus– in the muscular part of the right
crus of the diaphragm at the level of T10 to left of the
median plane
Transmits esophagus, vagi (anterior & posterior),
esophageal branch of left gastric artery
Caval opening – at the level of T8, to the right of the
median plane with in the central tendon
Transmits IVC, branch of right phrenic nerve, lymph
vessels from liver
39

40. Arteries
Superior surface
• Superior phrenic artery (thoracic aorta)
• Musculophrenic and pericardiacophrenic artery
(internal thoracic artery)
• Inferior surface: inferior phrenic artery
Veins
The superior surface
• Pericardiacophrenic and musculophrenic veins
(internal thoracic veins)
• Superior phrenic vein (IVC)
The inferior surface: inferior phrenic veins. The right
into the IVC, the left into left supra renal vein.
40

41. Nerve supply
– Phrenic (motor and sensory)
– Lower six intercostal and subcostal for peripheral
part (sensory)
Lymphatic drainage
– Thoracic surface to phrenic nodes
– Abdominal surface to lateral aortic nodes
– The two surfaces communicate freely
41

42. Respiratory movements
• Breathing or pulmonary ventilation consists of
two phases
Inspiration: the period when air flows into the
lungs
Expiration: the period when gases exit the lungs
• Lungs expand during inspiration and retract
during expiration.
42

43. Inspiration
• During inspiration the lungs increase in volume by
enlarging in all dimensions
• Air flows from areas of high pressure to areas of low
pressure to equalize the pressure within the lung to
that outside the lung
• During normal quiet inspiration, the diaphragm and
external intercostal muscles produce the muscle
movement
43

44. Action of diaphragm during Inspiration
• When the dome shaped
diaphragm contracts, it
moves inferiorly and
flattens
• As a result, the vertical
dimension of the
thoracic cavity increases
44

45. Action of External intercostal during Inspiration
• The external intercostal
muscles contract to raise
the ribs
• Because the ribs normally
extend anterio-inferiorly
from the vertebral column,
lifting them enlarges both
the lateral and anterior
dimensions
45

46. 46

47. Deep inspiration
• During deep or forced inspiration, additional muscles
contract and further increase thoracic volume
• The rib cage is elevated by the scaleni and sterno-
cleidomastoid muscle
• Scapulae are elevated and fixed by trapezius, levator
scapulae, rhomboids so that serratus anterior and
pectoralis minor act on ribs
47

48. Expiration
• As the respiratory muscles
relax, the rib cage drops under
the force of gravity and the
relaxing diaphragm moves
superiorly
• At the same time, the many
elastic fibers within the lungs
recoil
• As a result, the volume of the
thorax and lungs decrease
simultaneously, which pushes
air from the lungs
48

49. Forced expiration
• Quiet expiration in healthy people is a passive process
• Forced expiration is an active process produced
primarily by:
– The external & internal oblique,
– Rectus abdominis and
– Transverse abdominis muscles
• The internal intercostal muscles, quadratus
lumborum and the latissimus dorsi also help to
depress the rib cage 49

50. Nerves of thoracic wall
• 12 pairs of thoracic spinal nerves
• Leave spinal cord through corresponding intervertebral
foramina and divide into 2 branches
 Posterior (dorsal) rami: innervate muscles, bones,
joints and skin of the back
 Anterior (ventral) rami: innervate intercostal
musculature, and skin of the thorax (dermatome)
– Ventral rami of T1-T11= intercostal nerves
– Ventral ramus of T12 = subcostal nerve
50

51. Intercostal Nerves
• Each enters an intercostal space between the parietal
pleura and the posterior intercostal membrane.
• It then runs forward between the innermost intercostal
and internal intercostal muscle.
• Supply successive segments of thoraco abdominal wall
(dermatome and myotome).
 T1–T2 : also supply upper limb.
 T3 - T6: only intercostal region, typical.
 T7-T11: intercostal region + abdominal wall.
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53. Arteries of thoracic wall
The arterial supply to the thoracic wall derives
from the:
• Thoracic aorta, through the posterior
intercostal and subcostal arteries.
• Subclavian artery, through the internal
thoracic and supreme intercostal arteries.
• Axillary artery, through the superior and
lateral thoracic arteries.
53

54. Intercostal arteries
• Intercostal vessels run in the costal groove
1. Posterior intercostal arteries
1st & 2nd- arise from superior intercostal
artery (a branch of costocervical trunk of
subclavian artery)
3rd -11th & subcostal artery- branches of
the thoracic aorta
Accompanies intercostal nerve
54

55. 55

56. Intercostal arteries…
2. Anterior intercostal arteries
1st – 6th – from internal thoracic
7th- 9th – from musculophrenic
10th & 11th – have no anterior intercostal
Anastomose with the posterior vessels in the
intercostal spaces around the midclavicular
line
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58. The internal thoracic artery
Origin – Arise from the first parts of the
subclavian arteries.
• Descend into the thorax posterior to the clavicle
and 1st costal cartilage.
Termination - Terminate in the 6th intercostal
space by dividing into the superior epigastric and
the musculophrenic arteries.
58

59. Branches of ITA
• Anterior intercostal arteries for the upper six
intercostal spaces
• Pericardiacophrenic artery, which
accompanies the phrenic nerve and supplies the
pericardium and diaphragm.
• Mediastinal arteries to the contents of the
anterior mediastinum (e.g., the thymus)
59

60. 60

61. Intercostal veins
Right
1st – right brachiocephalic vein
2nd, 3rd & 4th - join to form superior intercostal
which drain into azygos vein, then to SVC
5th - 11th & subcostal (12th) – drain directly to azygos
vein.
Left
1st – left brachiocephalic vein
2nd, 3rd & 4th – join to form superior intercostal
which drain into left brachiocephalic
5th - 8th – drain into accessory hemiazygos vein
9th -11th & subcostal (12th) – drain into hemiazygos
vein.
61

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63. The internal thoracic veins
• Accompany the arteries (venae comitantes)
• Drain into brachiocephalic vein
• Intercostal vein, artery & nerve form a
neurovascular bundle lying between internal
intercostals and innermost intercostals in
costal groove
63

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