The Thoracic Cage by Prof. A. U. Ekanem.pdf

The Thoracic Cage by Prof. A. U. Ekanem.

1. THORACIC CAGE

2. The thoracic cage
•
•
•



The thoracic cage, also known as the rib cage, is the
osteocartilaginous structure that encloses the thorax
It is conical in shape: narrow above, and broad below

 It comprises of:
the 12 pairs of ribs and their associated costal cartilages 
the 12 thoracic vertebrae with their intervertebral discs
the sternum

6. FUNCTIONS OF THE THORACIC CAGE
•
•
•
The main function of the thoracic cage is to protect the vital structures
within it (e.g. heart, lungs, the great vessels, etc)

The thoracic cage also facilitates the act of breathing by resisting the
negative pressure generated by the elastic recoil of the lungs
and respiration-induced movements

The movement of the ribs also help in breathing by altering the intrathoracic
volume, thereby regulating inhalation and exhalation

7. •
•
The thoracic cage also provides attachments for extrinsic skeletal
muscles of the neck, upper limbs, upper abdomen and back

Together with the overlying skin and associated fascia and muscles,
makes up the thoracic wall.

8. THE RIBS
•
•
•
•
•
Ribs are flat, narrow and curved bones that form the most part of the rib cage

There are 12 pairs of ribs. The ribs are numbered 1–12 in accordance with the
thoracic vertebrae to which they attach posterioirly.

They articulate with the vertebral column posteriorly, and terminate anteriorly by
articulating with cartilage (known as costal cartilage).

In most of the ribs (R1 to R10), the costal cartilage then attaches to the sternum
either directly or indirectly.

The costal cartilages allows for expansion of the thoracic cage during inhalation

9. Classification of ribs
•
•
•
•
Based on physical features, there are two classifications of ribs – typical and atypical.

The typical ribs have a generalised structure, while the atypical ribs have variations on
this structure.

Typical Ribs: 3rd–9th ribs
The typical rib consists of a head, neck, tubercle and body

The head is wedge shaped, and has two articular facets separated by the crest of the
head. One facet articulates with the numerically corresponding vertebra, and the
other articulates with the vertebra above.

The neck contains no bony prominences, but simply connects the head with the body.
Where the neck meets the body there is a roughed tubercle.

10. •
•
•
Tubercle: located at the junction of the neck and body; a smooth
articular part articulates with the corresponding transverse process of
the vertebra, and a rough nonarticular part provides attachment for
the costotransverse ligament

The body, or shaft of the rib is flat and curved. This curvature is most
markedly at the costal angle where the rib turns anterolaterally.
The internal surface of the shaft has a groove for the neurovascular
supply of the thorax, protecting the vessels and nerves from damage.

13. •
•
Atypical Ribs
Ribs 1, 2, 10 11 and 12 can be described as ‘atypical’ – they have features
that are not common to all the ribs.
Rib 1 is shorter and wider than the other ribs. It only has one facet on its
head for articulation with its corresponding vertebra (there is no thoracic
vertebra above it). The superior surface is marked by two grooves, which
make way for the subclavian vessels.

14. •Rib 2 is thinner and longer than rib 1, and has two articular facets on
the head as normal. It has a roughened area on its upper surface, from
which the serratus anterior muscle originates

15. •
•
Rib 10 only has one facet – for articulation with its numerically
corresponding vertebra.
Ribs 11 and 12 have no neck, and only contain one facet, which is for
articulation with their corresponding vertebra.

16. Articulation of the rib with the thoracic vertebrae

17. •
•
•
•
•
Based on the attachment to the sternum, there are three types of ribs –
True Ribs: They are also called vertebrosternal ribs since they articulate on the
thoracic vertebrae and directly with the sternum by costal cartilages.
First to seventh ribs are true ribs.
These ribs articulate with the sternum by forming a sternocostal joint.

False Ribs: These ribs indirectly articulate with the sternum because their
costal cartilages are attached to the costal cartilage of the seventh rib.
Eight, ninth and tenth ribs are false ribs. The 8th, 9th and 10th cartilages
articulate with the costal cartilages just superior to them, forming a
continuous, articulated, cartilaginous costal margin of the rib cage.  These are
also called vertebrochondral ribs.

18. •
•
•
•
Floating Ribs: These ribs do not articulate with the sternum at any
point. Eleventh and twelfth ribs are floating ribs. They are also called
vertebral ribs. Their small costal cartilages at their anterior ends
enters the musculature in the lateral abdominal wall.

The spaces between the ribs are known as intercostal spaces

they contain the instrinsic intercostal muscles and the neurovascular
bundles containing intercostal nerves, arteries and veins.

There are 11 intercostal spaces, and each space is named according to
the rib which is the superior border of the space.

19. •
•
•
For example, the 6th intercostal space is located between the 6th and
7th rib. 

The superficial surface of the rib cage is covered by the thoracolumbar
fascia, which provides external attachments for the neck, back,
 pectoral and abdominal muscles.

The space inferior to the 12th rib is referred to as the subcostal space. 

20. The sternum
•The sternum is a vertical bone located in the midline of the thoracic cage. It
forms the anterior portion of the chest wall.

21. •
•
•
•
•
•
The sternum consists of three distinct bony parts:
The manubrium
The body of sternum
The xiphoid process

The manubrium is the superiormost part of the sternum. It is also
thicker and wider than other parts of the sternum.

The manubrium forms articulations with the clavicle (sternoclavicular
joint), body of the sternum (manubriosternal joint), first rib and
superior half of the second rib (sternocostal joints)

22. •
•
•
•
•
The superior border of the manubrium has a shallow, U-shaped border
called the jugular (suprasternal) notch.
The extent of the manubrium corresponds with T3 to T4 vertebrae

The body of the sternum extends from the manubrium to the xiphoid
process (i.e from T5 to T9 vertebrae).
Superiorly, the body articulates with the manubrium and
forms the manubriosternal joint and an anterior projection called
the sternal angle (of Louis).
The sternal body bilaterally articulates with six ribs (2nd to 7th rib) on
its lateral borders. In addition, inferiorly the body articulates with the
xiphoid process and forms the xiphisternal joint

23. •
•
•
The xiphoid process is the smallest and most inferior portion of the
sternum, positioned at the level of the T10 vertebra. 
The xiphoid process is cartilaginous. It calcifies as one ages
The xiphoid process is part of the inferior margin of the thoracic cavity
and marks the infrasternal angle (subcostal angle) of the inferior
thoracic aperture. 

24. The thoracic vertebrae
•

The thoracic vertebrae are a group of 12 irregular bones that form the
thoracic portion of the vertebral spine. 
The characteristic features that distinguishes the thoracic vertebrae from the
other vertebrae include:
•Vertebral body (corpus) is heart shaped.
Bilateral costal facets (demifacets) on the vertebral bodies, usually occurring
in inferior and superior pairs, for articulation with the heads of ribs.
• Costal facets on the transverse processes for articulation with the tubercles
of ribs, except for the inferior two or three thoracic vertebrae.
• Long, inferiorly slanting spinous processes. This serves to protect the spinal
cord by preventing objects like knife from reaching the spinal cord.

26. •
•
According to their structure, the thoracic vertebrae can be typical
and atypical.

The typical vertebrae have all the general features of the thoracic
vertebrae. They are T2 to T8.

27. •
•
•
•
•
The atypical thoracic vertebrae display variation in the size, location
and number of their superior and inferior costal facets.
T1 – Superior facet is not a demifacet, as this is the only vertebrae to
articulate with the 1st rib.
T9 resembles a typical thoracic vertebra except that the body has only
the superior costal facets (demifacets). The inferior costal demifacets
are absent.
T10 – A single pair of whole facets is present which articulate with the
10th rib. These facets are located across both the vertebral body and
the pedicle.
T11 and T12 – Each have a single pair of entire costal facets, which are
located on the pedicles.

29. •
•
•
•
•
Ligaments of the vertebral column and costovertebral joints
A number of small ligaments also support the costovertebral joints:
Radiate ligament of head of rib – Fans outwards from the head of the rib to
the bodies of the two vertebrae and intervertebral disc.
Costotransverse ligament – Connects the neck of the rib and the
transverse process.
Lateral costotransverse ligament – Extends from the transverse process
to the tubercle of the rib.
Superior costotransverse ligament – Passes from the upper border of the
neck of the rib to the transverse process of the vertebra superior to it.
Intertransverse ligament – between the transverse processes of the
thoracic vertebrae

32. Joints of the thoracic cage
•
•
•
•
•
The joints forming the domed-shaped thoracic cage include the:
Xiphisternal joint – between the xiphoid process and body of sternum. No
movement normally occurs at these joints.

Intervertebral joints – between vertebrae

Sternocostal (sternochondral) joints – are formed by the lateral borders of the
sternum and the costal cartilages of the 1st to 7th ribs. The first pair of costal
cartilages articulate with the manubrium sternum.  The second to seventh pairs of
costal cartilages articulate with the body of the sternum at synovial joints,
allowing movement during respiration.

Sternoclavicular joints – between the manubrium and clavicles

Manubriosternal joints – between the manubrium and body of sternum. In children,
slight movement is noticed at this joint during forced breathing

33. •
•
•
i.
ii.
iii.
•
Costochondral joints – costal cartilage and rib
Interchondral joints – joining the costal cartilages to one another.
Costovertebral joints – formed by the ribs and bodies of the vertebrae.
Each costovertebral joint consists of the head of the rib articulating
with:
Superior costal facet of the corresponding vertebra
Inferior costal facet of the superior vertebra
Intervertebral disc separating the two vertebrae
Within the costovertebral joint, the intra-articular ligament of head of
rib attaches the rib head to the intervertebral disc. Only slight gliding
movements can occur at these joints, due to the close articulation of
their components.

34. •







The costotransverse joints are formed by the articulation of transverse
processes of a thoracic vertebra and the tubercle of the adjacent rib.
They are present in all vertebrae except T11 and T12

35. Clinical Anatomy
1.Rib fractures most commonly occur in the middle ribs, as a
consequence of crushing injuries or direct trauma. A common
complication of a rib fracture is further soft tissue injury from the
broken fragments. Structures most at risk of damage are the
lungs, spleen or diaphragm.

36. •If two or more fractures occur in two or more adjacent ribs, the affected
area is no longer under control of the thoracic muscles. It displays a
paradoxical movement during lung inflation and deflation. This condition is
known as flail chest. It impairs full expansion of the ribcage, thus affecting
the oxygen content of the blood.

38. 2. Supernumerary rib: This occur most commonly as a cervical rib arising
from C7 or a lumbar rib arising from L1. In extremely rare situations, there can
be sacral, coccygeal, intrathoracic, or aberrant lumbar ribs. Rarely
supernumerary ribs (cervical and lumbar ribs aside) have been found as
'normal' anatomic variants, without evidence of any clinical sequelae, but may
confuse the identification of vertebral levels in radiographs and other diagnostic
images.
However, cervical rib may compress the brachial plexus/subclavian artery;
causing Klumpke’s paralysis/ischemia

3. Jeune's Syndrome is a form of congenital dwarfism causing children to have a
deformity of their chest wall. The chest cage is extremely small and doesn't
have enough room for proper breathing. The ribs are broad, short and irregularly
joined between the cartilage and sternum, or breastbone.

39. Juene Syndrome

40. 4. Spondylocostal and spondylothoracic dysplasia (or dysostosis), a rare
condition characterized by abnormal development of the spine and ribs.
People with this condition can have fused or missing ribs as well as an
abnormally curved spine (scoliosis) caused by misshapen or fused
vertebrae.

41. •
•
5. Dislocation of sternocostal and interchondral joints
Sternocostal and/or sternochondral joint dislocation is the
displacement of a costal cartilage from the sternum. This leads to
dislocation of the corresponding rib, a condition referred to as slipping
rib syndrome.

Displacement of interchondral joints usually occurs unilaterally and
involves ribs 8,9, and 10. Trauma sufficient to displace these joints
often injures underlying structures such as the diaphragm and/or liver,
causing severe pain, particularly during deep inspiratory movements

42. 6. Thoracic insufficiency syndrome is the inability of the thorax to support
normal respiration or lung growth. The rare condition of fused ribs and
congenital scoliosis may result in a three-dimensional thoracic deformity
with adverse effects on thoracic growth and function with development
of thoracic insufficiency syndrome.