Sternum

The sternum (plural: sterna or sternums) completes the anterior chest wall as the ventral breastplate.

Gross anatomy

The sternum is composed of a manubrium, a body and the inferior xiphisternum (a.k.a. xiphoid process). They articulate via secondary cartilaginous joints via hyaline cartilage with a fibrocartilaginous intervening disc:

  • the manubrium is flat and four-sided, wider superiorly
  • the body is a flat rectangular bone that has grooves (facets) on its lateral border for articulation with the ribs:
    • approximately 20 cm long
    • 3-4 cm wide
    • 1 cm thick
  • the xiphoid process is a thin bony projection inferiorly
Articulations
  • superiorly the manubrium attaches to the neck where the two deep layers of cervical investing fascia insert
  • the manubrium articulates with the first rib (primary cartilaginous), clavicle (atypical synovial), and body of the sternum (secondary or primary cartilaginous joint) 
  • the body articulates with the second rib at the sternomanubrial angle (of Louis , which is in the transthoracic plane of Ludwig) as well as the 3 to 7 rib and costal cartilages
    • the articulations of 2 and 7 ribs are shared as demifacets between each of the manubrium and the body, and the body and the xiphoid respectively 
  • inferiorly articulates with xiphisternal joint, a secondary cartilaginous joint (symphysis)
Attachments
Musculotendinous
Ligamentous

Arterial supply

Venous drainage

Innervation

  • nerve supply is via intercostal nerves which arise from the anterior rami of thoracic spinal nerves

Lymphatic drainage

Variant anatomy 

See also