This document provides an overview of the anatomy seminar on the chest wall and diaphragm with clinical correlations. It begins with an outline and then discusses the anatomy of the chest wall including bones like the sternum and ribs, muscles, blood vessels, and nerves. It then covers the anatomy of the diaphragm including its origin, insertion, openings, blood supply and innervation. Finally, it discusses some normal anatomical variants and imaging abnormalities that can be seen involving the chest wall and diaphragm.

1. ANATOMY SEMINAR ON CHEST WALL AND DIAPHRAGM
WITH CLINICAL CORRELATIONS
DR. ADUGNA DAGNE (YEAR 1 RADIOLOGY RESIDENT)
ST.PAUL HOSPITAL MELLINIUM MEDICAL COLLEGE
May -2018
6/12/2018
1

2. OUTLINE
• Chest wall
• Diaphragm
• Anatomy-related imaging abnormalities
• References
6/12/2018 2

3. Chest Wall Anatomy
• Skin, subcutaneous fat
• Blood vessels, lymphatics, nerves
• Bone( thoracic cage), cartilage
• Muscles
• Endothoracic fascia, fibroelastic connective tissue between inner aspect
of chest wall and costal pleura
6/12/2018 3

4. Function
• Musculoskeletal cage: Surrounds cardiorespiratory system; affects
respiration by expanding and contracting during ventilation
6/12/2018 4

5. Thoracic Inlet
• Opening at superior end of thoracic rib cage;
conduit for cervical structures to enter thorax
• Bound by T1 vertebral body, right and left 1st ribs
and their costal cartilages, and manubrium of
sternum
Contents
• Great vessels heading for neck and upper limb
- CCA, IGV and S. artery and vein
• Esophagus ,Trachea
• Nerves and lymphatic system
6/12/2018 5

6. Thoracic Outlet
• Opening at inferior end of thoracic rib cage;
conduit for thoracic structures to exit thorax
• Bound by T12 vertebral body, right and left
12th ribs, costal cartilages of 7th-12th ribs,
xiphisternal joint plus diaphragm
6/12/2018 6

7. SKELETAL STRUCTURES
• Includes thoracic vertebrae, shoulder girdle, sternum, clavicle
,scapula and ribs with their cartilage
6/12/2018 7

8. Sternum
• Flat, broad bone forms the anterior midline portion of the
thoracic cage
Consists of:
• Manubrium(T3/4) – triangular shape, has notch, provides
articulation for clavicles, 1st and upper part of 2nd ribs
• Body – consists of four parts(sternebrae), which fuse by the
age of 25 and articulate with 2nd–7th costal cartilages;
• The junction of the body with the manubrium (angle of
Louis) is at T4/5
• Xiphoid process(T10) – often remains cartilaginous
The xiphisternal joint can be confused with a fracture.
Fusion to the sternal body occurs at age 40 years.
6/12/2018 8

9. 6/12/2018 9

10. • The sternum is difficult to assess on a frontal view and best seen on lateral/oblique views, CT is best
6/12/2018 10
Lateral sternal view: the sternum (3) is shown articulating with the
manubrium (4) and the retrosternal fat space (5). Manubriosternal joint (6)

11. Anatomy-related imaging abnormalities of the sternum
1.On a PA CXR ;manubrial borders may simulate mediastinal widening
2. Pectus excavatum or funnel chest
• Is a depression of the lower sternum
• The most common congenital abnormality
• Mimics right middle lobe disease
• Asymptomatic but is associated with a greater prevalence of CHD
• When marked, it results in a reduction in the prevertebral space,
thereby causing leftward displacement and axial rotation of the heart,
and a reduction in the space occupied by the left lung
6/12/2018 11

12. Fig PA CXR: indistinct right heart border plus displacement of the heart to the left, exaggerated
vertical course of the anterior rib
Lateral CXR; same patient posterior displacement of the sternum with narrowing of APD
6/12/2018 12

13. 3. pectus carinatum or pigeon breast ;is abnormal protrusion of
the mid portion of sternum.
• A less common congenital abnormality
• Although it can occur in isolation, is seen with increased
frequency in patients with cyanotic congenital heart disease.
6/12/2018 13

14. PA CXR; Normal (pectus carinatum)
Lateral CXR; outward bowing of the sternum with Incresead APD
6/12/2018 14

15. Ribs
• 12 pairs, with the 1st thoracic vertebra
associated with the 1st rib
• 1-7 form direct articulations with the
sternum via costal cartilage (true)
• Ribs 8-10 reach costal cartilage above,
forming indirect articulations (false)
• 11 and 12 lack anterior attachment (floating)
, short costal cartilages terminate in
abdominal wall muscle
6/12/2018 15

16. Each rib consists of:
• Head; 2 faces for articulation with vertebral bodies; e.g the 6th rib
articulate with the bodies of 5th and 6th vertebrae(synovial)
• Neck located between head and tubercle of each rib ; for attachment of
the costo-transverse ligament
• Tubercle (1-10) with articular and non articular process
• Body/shaft: Longest part of each rib
divided into two parts by the angle, which is the lateral limit of the
attachment of the erector spinae muscle
• Angle: Most posterior part
• Costal groove on inner surface of inferior border; for IC NVB
6/12/2018 16

17. 6/12/2018 17

18. • The first rib is the shortest,
with a prominent tubercle for
the attachment of the
scalenus anterior.
• The subclavian vein runs
anterior to the tubercle and
the subclavian artery and
lowest trunk of the brachial
plexus run in a groove
posteriorly
6/12/2018 18

19. Anatomy-related imaging abnormalities of rib
• Prominent 1st and 2nd ribs and cervical ribs in the
supraclavicular fossa can mimic a clinical mass.
• Congenital abnormalities of modelling may be
confined to 1or 2 ribs or be generalised.
• One or a few upper ribs are commonly bifid,
splayed, fused or hypoplastic.
• Usually occurring in isolation, occasionally part
of a syndrome (e.g. basal cell naevus syndrome)
or other anomalies (e.g. Sprengel’s deformity).
6/12/2018 19

20. • Cervical rib occurs in 1-2 % of people and is
bilateral in 50%. These are bony or fibrous
bands
• It arise from C7 transverse process and
articulates with the first rib
• Sharp lines along the lower costal margin. PA
CXR shows sharp, thin lines along the lower
margin of the ribs (arrows)
• This is a normal finding which can be mistaken
for rib erosion or malignancy
6/12/2018 20
Fig. (a) Radiograph of thoracic inlet. Cervical ribs arise from down
pointing cervical transverse processes
a thin, sharp hairline caused by the cortex of the costal groove

21. • A prominent first costochondral junction
can be mistaken for a mass on a CXR or CT
due to partial volume averaging
6/12/2018 21
(a) Axial CT: lung windows and (b) soft tissue mediastinal windows; the first rib (1) on CT due to partial
volume averaging can give the impression of a mass on the lung windows.

22. • The rhomboid fossa is a variable, frequently
irregular concavity in the undersurface of the
medial clavicle above the costal cartilage of
the first rib, more common in males.
• This normal variant should not be mistaken
for a lytic or erosive process.
• May simulate an apical cavity on a CXR
6/12/2018 22
Fig; Rhomboid fossa. Note the irregular defect in the inferior medial clavicle adjacent to the
first rib (arrows). give rise to the costoclavicular ligament

23. MUSCLES
Pectoral;
• Pectoralis major: Largest muscle in
breast and pectoral region; originates
from anterior chest wall, sternum, and
clavicle;
: adducts, flexes, and medially
rotates arm
• Pectoralis minor: Deep to pectoralis
major; originates from
chest wall, inserts onto coracoid
process of scapula;
: stabilizes scapula
6/12/2018 23
Axial CECT ; at the level of aortic arch branches

24. Intercostal muscles;
1. External: Contained within 11 ICS; extend from tubercle of ribs to costochondral
junction
2. Internal: Middle layer; occupy 11 ICS ; extend from border of sternum to angle of
ribs
3. Innermost: Form inner layer of chest wall muscles with subcostales and
transversus thoracis muscles
Serratus Anterior
• Thin muscular sheet; overlies lateral thoracic cage and intercostal muscles; arises
from upper 8 ribs; wraps around rib cage; inserts along medial border of anterior
surface of scapula
6/12/2018 24

25. Back Muscles
• Superficial extrinsic muscles (connect
upper limbs to trunk; limb
movement); trapezius, latissimus
dorsi, levator scapulae, rhomboids
• Intermediate extrinsic muscles
(superficial respiratory muscles);
serratus posterior
• Deep intrinsic muscles (postvertebral
muscles; control posture, vertebral
and head movement)
; splenius muscle, erector spinae
muscles, deep transverso-spinales
muscles
6/12/2018 25
Axial CT scan at the level of supraclavicular region

26. Veins;
• IC veins drain into azygous and
hemiazygous veins,
except 1st on right drains into
vertebral or BC vein and
2nd and 3rd on left form the
superior intercostal vein, which
crosses the aortic arch to drain
into left BC vein
6/12/2018 26

27. Arteries;
by anterior and posterior ICA
Anterior ICA; arise from
internal thoracic artery:
Branch of subclavian artery;
descends posterior to 1st 6
costal cartilages; end by SEA
and MPA
Posterior ICA; arise from
decending aorta and
superior ICA
6/12/2018 27

28. Anterior Intercostal Arteries
Each anterior ICS contains two anterior
intercostal arteries (except in the lower
two inter-costal spaces).
a. The upper 6 pairs arise from the
internal thoracic artery.
b. The 7th, 8th, and 9th pairs arise from the
musculo-phrenic artery.

29. Posterior Intercostal Arteries
- Each posterior ICS contains one posterior intercostal
artery which runs in the costal groove .
- Each artery gives a collateral branch
which runs over the upper border of the rib below.
-spinal branch
* The upper two posterior ICA superior intercostal
artery (from the costo-cervical trunk)
* From 3 - 11 posterior ICA and subcostal artery 
descending thoracic aorta.

30. Intercostals neurovascular bundle
• Consist of:
o Vein – most superior
o Artery
o Intercostals nerve – most inferior
• Runs just inferior to each rib, deep
to the internal intercostals
superficial to the innermost
intercostal (i.e. between the
internal and innermost)

31. Intercostal Nerves
- There are 11 intercostal nerves in the upper 11 intercostal spaces and a
subcostal nerve below the last rib (on each side).
- Each intercostal nerve arises from the ventral ramus of the
corresponding thoracic spinal nerve.

32. Lymphatics
• Chest wall drainage through thoracic duct (right upper limb,
right face and neck drained by right lymphatic duct)
6/12/2018 32

33. Diaphragm
6/12/2018 33

34. It is a double domed,musculotendinous
partition separating the thoracic &
abdominal cavities.
It is a chief muscle of inspiration
It is formed of a peripheral muscular
part & centrally placed tendon

35. Origin:
Sternal origin:
By 2 slips (right & left) from the
inner surface of the xiphoid
process
1
Costal origin:
From lower six ribs & their costal
cartilages2
Vertebral origin:
Arise by means of (crura) &
(arcute ligaments)
3

36. Vertebral Origin
Crura:
Right crus:
From the bodies of upper 3
lumbar vertebrae (L1,L2 & L3) &
their intervertebral discs.
Left crus:
From the bodies of the upper 2
lumbar vertebrae (L1 & L2 ) & their
intervertebral discs.

37. Lateral to crura the diaphragm arises
from the medial & lateral arcuate
ligaments
Medial arcuate ligaments:
is the thickened upper margin of
the fascia covering the anterior
surface of psoas major muscle
Vertebral origin
Lateral arcuate ligaments:
is the thickened upper margin of the
fascia covering the anterior surface of
quadratus lumborum muscle

38. Medial borders of the two crura connected by a median arcuate ligaments
which crosses over the anterior surface of the aorta (T12)
Median
arcuate
ligament

39. INSERTIONIt is inserted into a central
tendon which is shaped
like 3 leaves (Trifle)
Muscular portions
converge medially as
aponeurosis
(central tendon)
○ Central tendonis fused
to inferior aspect of
fibrous
pericardium but has no
osseous attachment

40. There are three main openings and two potential gaps
• Aortic
• Esophageal
• Vena cava
• The foramina of Morgagni
• The foramina of Bochdalek
6/12/2018 40

41. Structures that pierce the diaphragm
The structures that pierce the diaphragm are as follows:
•Terminal branches of the left phrenic nerve pierce the central
tendon;
•The greater,lesser and least splanchnic nerves,which pierce
each crus;and
•The lymph vessels between the abdomen and thorax, which
pierce the diaphragm throughout, especially posteriorly.
6/12/2018 41

42. MAJOR OPENINGS
Aortic opening – T12
Aorta
Thoracic duct ; Hemiazygos
Azygos vein
Esophageal opening–T10
Esophagus
Vagus nerve
Esophageal branches of left gastric artery
and veins &
Lymph vessels
Caval opening – T8
IVC
right phrenic nerve

43. Openings cont….
The foramina of Morgagni
 triangular gaps in the muscles of the anteromedial
diaphragm
 occupied by fat and the internal mammary
vessels
 potential intrathoracic herniation of abdominal
contents.
The foramina of Bochdalek
 defects in the closure of the posterolateral
diaphragm at the junction of the pleuroperitoneal
membrane with the transverse septum

44. Blood Supply of the diaphragm
Superior surface:
Pericardiacophrenic &
Musculophrenic arteries
(internal thoracic)
Inferior surface:
Inferior phrenic arteries
(abdominal aorta)
Venous drainage –inferior
phrenic vein

45. Nerve Supply of the diaphragm
Motor through phrenic nerve (C3, 4 & 5)
Sensory supply to the central tendon
(phrenic nerve)
But the sensory supply from the
periphery is from the lower five
intercostal nerves & subcostal nerve.

46. Imaging and anatomy-related imaging abnormalities
of the diaphragm
6/12/2018 46

47. NORMAL VARIANTS
1 – SCALOPPING – short curves of diaphragm convex
upward; Rt side
2 – MUSCLE SLIP – small curved lines, concave upward;
seen in tall, thin patients & emphysema; right side
3 – DIAPHRAGMATIC HUMP – mild form of
eventration with incomplete muscularization but no
muscle defect
4-EVENTRATION – result of congenital absence or
under development of diaphragmatic
musculature. (muscle replaced by ct and fibrous
tissue) nearly Lt sided, hemidiaphragm considerably
elevated with marked mediastinal displacement to
the rt;
47

48. 48
Fig; Focal eventration.(A, B) PA and lateral chest radiograph reveal a soft-tissue opacity arising from the
diaphragm. (C, D) CT shows the presence of liver under the elevated part of the diaphragm.

49. Sagittal CECT shows the liver bulge that is
characteristic of eventration (congenital
thinning) of the diaphragm, usually an
asymptomatic condition 49
Axial NECT; finger-like "slips" of the diaphragm may
indent the surface of the liver. Each of the slips is
outlined by the adjacent subdiaphragmatic fat

50. chest X-ray for diaphragmatic imaging
The aims
(1) Looking for diaphragmatic pathology
(2) Deciding whether the abnormality is indeed located in the
diaphragm or whether what is seen is secondary to other disease
(3) Identify variable presentation of the diaphragm, many
changes seen on a chest X-ray are not always related to
pathology

51. The right hemidiaphragm is usually 1–1.5 cm
higher than the left , but may be at the same
level.
On a lateral film the gastric air bubble is below
the left hemidiaphragm and the anterior
portion is not seen as it is silhouetted by the
heart
6/12/2018 51

52. • On CXR, the diaphragmatic
muscle is only visible
when air is present above
and below it.
• presents as a 2- to 3-mm-
thick line between the air-
containing lung and the
abdominal air

53. Ultrasound
• Using the liver or spleen as an
acoustic window, shows diaphragm as
thin echogenic line
• Diaphragmatic motion is ideally
assessed sonographically
• Eventration of the diaphragm can
mimic paralysis on Us
• Diaphragmatic masses
• Assess the integrity of the diaphragm

54. CT scan
• The diaphragm is not usually visible as a
structure discrete from the liver or other
abdominal organs, unless there is a lot off at
on its abdominal aspect.
• The costal origins may be prominent with
deep inspirations.
• The crura are usually visible on the anterior
surface of the upper lumbar vertebrae
6/12/2018 54

55. Costal cartilaginous origin anterolaterally
Costal origin laterally

56. Diaphragm is not impermeable
○ Ascites, pleural effusion, tumor, infection, or extraluminal air may pass
from abdomen into thorax (and vice versa)
6/12/2018 56

57. MRI
• The primary modality for the imaging of most congenital and
acquired thoracic vascular disorders
• superior contrast resolution between tumor and fat
• Superior to CT in the diagnosis of chest wall or mediastinal
invasion
• The ability to scan in direct sagittal and coronal planes, and the
lack of need for intravenous iodinated contrast

58. MRI cont….
The major disadvantages of thoracic MR scanning
the limited spatial resolution
the inability to detect calcium, and the difficulties in imaging
the pulmonary parenchyma
more time-consuming and expensive than CT

59. • Thank you
6/12/2018 59

60. References
• Applied radiologic anatomy
• Anatomy for diagnostic imaging
• Practical radiological anatomy
• Imaging of the chest expert radiology series
• Imaging anatomy of chest, abdomen and pelvis 2017
• Grainger and Allison’s Diagnostic radiology
• Diagnostic imaging
• Netter atlas
• Internet sources
• Previous seminars