The thoracic cage

Where is the thorax located?

Between the neck and tyhe abdomen

Consists of:

The thoracic cage, wall and cavity

The thoracic cage functions

Protects organs, assist in respiration, provides attachments for muscle

Component parts of the thoracic cage

12 thoracic vertebrae and their intervertebral discs
12 pairs of ribs and their costal cartilages
Sternum: manubrium, body of the sternum, xiphoid

1

Manubrium

2

Body of sternum

3

Xiphoid process

1

Articular facet for SC joint

2

Surface for rib I

3

Articular demifacet for rib II

4

Suprasternal notch

The intercostal space

Each rib is separated from its neighboring rib by an intercostal space
The intercostal spaces are named in relation to the rib aboce

True ribs

Ribs 1-7 are true ribs
Their costal cartilages articulate directly with the sternum

False ribs

Ribs 7-10 are false ribs
Their costal cartilages do not articulate directly with the sternum
Articulate with costal cartilage or rib above

Floating ribs

Ribs 11-12
Not articulated to the sternum

Typical and atypical

Ribs 3-9 are typical
Ribs 1,2 and 10-12 are atypical

Atypical ribs

10th rib: similar to typical rib with one articular facet on head
11-12 ribs: one articulate facet on head, no neck or tubercle, short, stright and pointed shaft

Costovertebral joints

Between posterior aspect of the ribs and the thoracic vertebrae

Intersternal joints

Between the bones of the sternum

Sternocostal joints

Between the costal cartilages and the sternum

Interchondral joints

Between the costal cartilages of the ribs 8-10 with the costal cartilage of teh rib above

Ribs II-IX joints head of ribs

Superior demifacet on head artiuclates with vertebra aboce
Inferior demifacet articulates with corresponding vertebra

Ribs I, X-XII

Only have on facet head
Artiuclate with corresponding vertebrae
Classifcation: synovial plane joints

Costotransverse joint

The articular facet on the tubercle of the ribs articulates with the transverse process of the corresponding throacic vertebra
Classification: synovial plane joints

Manubriosternal joint

Secondary cartilaginous joint

Xiphisternal joint

Secondary cartilogenous joint

1st sternocostal joint

Primary cartilaginous joint (resembles a fibrous joint)

2-7 sternocostal joint

Synovial plane joint

Interchondral joint

6-7, 7-8, 8-9 synovial plane joints
9-10 almost never synovial but a fibrous joint

Costochondral junctions

Primary cartilaginous joints

Joints of the thoracic cage movements

Each joint only has a small amount of movement
Collectively they allow the thoracic cage and ribs to move during breathing

Inspiration

Causes an incerase in the vertical height as well as the anterior posterior and transverse dimensions of the throacic cage