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
- muscular attachments: sternocleidomastoid, intercostal, pectoralis major, sternohyoid, and sternothyroid muscles
- transversus thoracis muscle arises from the posterior surface of the body
- the xiphisternum attaches to linea alba
Ligamentous
- sternopericardial ligaments secure the fibrous pericardium to it
- interclavicular ligament
- anterior and posterior sternoclavicular ligaments (thickenings of the sternoclavicular joint capsule)
Arterial supply
- nutrient branches from internal thoracic (mammary) artery
- deep to the sternum is the internal thoracic artery laterally
Venous drainage
- tributaries of the internal thoracic veins, posterolateral to the sternum
Innervation
- nerve supply is via intercostal nerves which arise from the anterior rami of thoracic spinal nerves
Lymphatic drainage
- chain of internal mammary lymph nodes
Variant anatomy
- episternal ossicle
- manubriosternal and sternoxiphoidal fusion
- sternal and xiphoid foramina
- sternal cleft and band
- sternal defect (notch)
- tilted sternum: oblique instead of horizontal orientation in the mediolateral plane
- suprasternal tubercle
- unfused sternal body segments
- xiphoid shape variations
See also
Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu Sternum: