Thoracic cage (also known as the rib cage) is a bony framework of the thoracic wall

It encloses the thoracic cavity

It is formed by

The sternum

12 pairs of ribs and their cartilages

12 thoracic vertebrae and their respective intervertebral discs

There are 12 pairs of ribs in the thoracic cage

Ribs are long, flat and curved bones that have a bony part posteriorly and cartilaginous part anteriorly

Each rib articulates with a vertebrae at two joints

Costovertebral joint – between the head of the rib and facets of two adjacent vertebral bodies

Costotransverse joint – between the costal tubercle and the transverse process of the vertebrae

The spaces between adjacent ribs and costal cartilages

Mainly filled with muscles and their membranes

Also contains intercostal nerves and blood vessels

There are 11 intercostal spaces

The space under 12th rib is called the Subcostal space

Intervertebral joints

Sternoclavicular joints

Sternochondral joints

Manubriosternal joint

Xiphisternal joint

Costochondral joints

Costovertebral joints

Costotransverse joints

Interchondral joints

There are five muscles that make up the thoracic cage

The intercostals

Subcostals

Transversus thoracis

These muscles act to change the volume of the thoracic cavity during respiration

The intercostal muscles lie in the intercostal spaces

External intercostal muscles

Internal intercostal muscles

Innermost intercostal muscles

Attachments

Originates at the lower border of the rib, and inserts into the superior border of the rib below

Originates from the lateral edge of the costal groove and inserts into the superior surface of the rib below

Originates from the medial edge of the costal groove and inserts into the superior surface of the rib below

Actions

Elevates the ribs, increasing the thoracic volume

The interosseous part reduces the thoracic volume by depressing the ribcage, and the interchondral part elevates the ribs

Innervation

Intercostal nerves (T1-T11)

Transversus Thoracis

Subcostal muscles

Attachments

From the posterior surface of the inferior sternum to the internal surface of costal cartilages 2-6

Originates from the inferior surface of the lower ribs, near the angle of the rib. They then attach to the superior border of the rib 2 or 3 below

Actions

Weakly depress the ribs

Share the action of the internal intercostals

Innervation

Intercostal nerves (T2-T6)

Intercostal nerves

Supporting the thorax

Protecting thoracic and abdominal organs from injury

Assisting in respiration

Providing support for the upper limbs

Providing attachment for muscles involved in upper limb motion