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

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
  • 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) 6
  • 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 3rd to 7th rib and costal cartilages
    • the articulations of 2nd and 7th 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 6 (symphysis)
  • nerve supply is via intercostal nerves which arise from the anterior rami of thoracic spinal nerves
Anatomy: Thoracic

Thorax

Article information

rID: 46816
Section: Anatomy
Synonyms or Alternate Spellings:
  • Sternums
  • Sterna
  • Sternum (anatomy)
  • Breastbone

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Cases and figures

  • Figure 1a: sternum (Gray's illustration)
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  • Figure 1b: sternum (Gray's illustration)
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  • Figure 2a: thoracic cage (Gray's illustrations)
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  • Figure 4: sternal and costal cartilage muscular attachments (Gray's illustration)
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  • Figure 2b: thoracic cage (Gray's illustrations)
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  • Figure 3: costochondral joints (Gray's illustration)
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  • Case 1: tilted sternum
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  • Case 1: honeycomb sterna
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