Twelfth rib
The twelfth rib is an atypical rib. It is the shortest rib, and one of two floating ribs.
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Gross anatomy
Osteology
The 12th rib has a single facet on its head for articulation with the T12 vertebra. It has a short neck and no tubercle. It also lacks a costal groove and angle. internal surface of this word about slopes slightly upwards.
The pointed anterior end of the 12th rib is covered with costal cartilage. Its length is highly variable.
Attachments
- quadratus lumborum: anterior inferior surface on the medial half
- internal intercostal muscle: medially at or near the upper border of the anterior surface
- external intercostal muscle: the upper border of the external surface
- diaphragm: laterally at or near the upper border
- lumbocostal ligament: posteriorly, near the head, running to the first lumbar transverse process
- levator costae: external surface medially
- longissimus thoracis: external surface medially
- iliocostalis: external surface medially
- serratus posterior inferior: external surface laterally
- latissimus dorsi: external surface laterally
- external oblique: external surface laterally
Related pathology
- infection, e.g. septic arthritis, osteomyelitis
- malignancy, e.g. chondrosarcoma, enchondroma, metastases
- trauma, e.g. fracture
- fracture of the twelfth rib is rare
- may be associated with retroperitoneal hemorrhage, adrenal/splenic/renal trauma, and thoracolumbar vertebral injury
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
- atrial septum
- endocardium
- myocardium
-
pericardium
- epicardium
- epicardial fat pad
- pericardial space
- oblique pericardial sinus
- transverse pericardial sinus
-
pericardial recesses
- aortic recesses
- pulmonic recesses
- postcaval recess
- pulmonary venous recesses
- pericardial ligaments
- 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
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