Bones and Joints of the Thorax

Flashcards covering the anatomical features, parts, articulations, and muscular attachments of the sternum and thoracic cage based on the lecture notes.

Thoracic cage components

The cage is formed by the sternum, $12$, pairs of ribs, and $12$ thoracic vertebrae.

Sternum (Breast bone)

An elongated flat bone lying in the anterior median part of the chest wall, measuring about $7\,cm$ long.

Sternum shape analogy

Resembles a dagger or sword, where the manubrium is the handle, the body is the blade, and the xiphoid process is the point.

Manubrium (Episternum)

The thickest and strongest part of the sternum, which lies opposite to the $3rd$ and $4th$ thoracic vertebrae.

Body of the Sternum (Mesosternum)

The middle part of the sternum, which is longer, narrower, and thinner than the manubrium and broadest at its lower end.

Xiphoid process (Metasternum)

The thin, pointed lower part of the sternum.

Sternal angle (Angle of Louis)

The junction between the manubrium and the body of the sternum, recognized by a transverse ridge on the anterior aspect.

Internal angle of the sternum

The manubrium and body of the sternum lie at an angle of $163^{\circ}$ to each other.

Sternal axis angle

The angle between the long axis of the manubrium and the long axis of the body of the sternum is about $17^{\circ}$.

Manubriosternal joint

A secondary cartilaginous joint formed between the lower border of the manubrium and the upper end of the body.

Xiphisternal joint

A primary cartilaginous joint formed between the lower end of the body and the xiphoid process.

Suprasternal notch (Jugular notch)

A thick, rounded, and concave notch on the upper border of the manubrium that provides attachment to the interclavicular ligament.

Clavicular notch

A feature on either side of the suprasternal notch that articulates with the clavicle to form the sternoclavicular joint.

Anterior attachments of the manubrium

Provides attachment to the sternal head of the sternocleidomastoid and pectoralis major muscles on each side.

Posterior attachments of the manubrium

Provides attachment to the sternohyoid (at the level of the clavicular notch) and the sternothyroid (at the level of the facet for the $1st$ costal cartilage).

Posterior relations of the upper half of the manubrium

Related to three branches of the arch of aorta: the brachiocephalic artery, left common carotid artery, and left subclavian artery, plus the left brachiocephalic vein.

Posterior relations of the lower half of the manubrium

The lower half of the manubrium is related to the arch of aorta.

First costal cartilage articulation

Articulates with the upper facet on the lateral border of the manubrium to form a primary cartilaginous joint.

Second costal cartilage articulation

Articulates via two demifacets located at the junction of the manubrium and the body of the sternum.