Sternum
The sternum (plural: sterna or sternums) completes the anterior chest wall as the ventral breastplate.
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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) 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)
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 5
- suprasternal tubercle
- unfused sternal body segments
- xiphoid shape variations
See also
Related Radiopaedia articles
Anatomy: Thoracic
- thoracic skeleton
- thoracic cage
- thoracic spine
- articulations
- muscles of the thorax
- diaphragm
- intercostal space
- intercostal muscles
- variant anatomy
- spaces of the thorax
- thoracic viscera
- tracheobronchial tree
-
lungs
-
bronchopulmonary segmental anatomy (Boyden Classification) (mnemonic)
- left lung
- right lung
- variant anatomy
- lung parenchyma
- hilum
- pleura
-
bronchopulmonary segmental anatomy (Boyden Classification) (mnemonic)
-
heart
- cardiac chambers
- heart valves
- pectinate muscles
- cardiac fibrous skeleton
-
coronary arteries
- coronary arterial dominance
- myocardial segments
-
left main coronary artery (LMCA)
- ramus intermedius artery (RI)
-
circumflex artery (LCx)
- obtuse marginal branches (OM1, OM2, etc))
- Kugel's artery
-
left anterior descending artery (LAD)
- diagonal branches (D1, D2, etc)
- septal perforators (S1, S2, etc)
-
right coronary artery (RCA)
- conus artery
- sinoatrial nodal artery
- acute marginal branches (AM1, AM2, etc)
- inferior interventricular artery (PDA)
- posterior left ventricular artery (PLV)
- congenital anomalies
- innervation of the heart
- fetal circulation
-
pericardium
- pericardial space
- oblique pericardial sinus
- transverse pericardial sinus
-
pericardial recesses
- aortic recesses
- pulmonic recesses
- postcaval recess
- pulmonary venous recesses
- pericardial ligaments
- epicardial fat pad
- esophagus
- thymus
- breast
- blood supply of the thorax
- arteries
- veins
- superior vena cava (SVC)
- inferior vena cava (IVC)
-
coronary veins
- cardiac veins which drain into the coronary sinus
- great cardiac vein
- middle cardiac vein
- small cardiac vein
- posterior vein of the left ventricle
- vein of Marshall (oblique vein of the left atrium)
- anterior cardiac veins
- venae cordis minimae (smallest cardiac veins or thebesian veins)
- cardiac veins which drain into the coronary sinus
- pulmonary veins
- thoracoepigastric vein
- lymphatics
- innervation of the thorax