Overview
The dog sternum is made of eight sternebrae joined by intersternal cartilage: the manubrium (manubrium sterni), six intermediate sternebrae forming the body, and the xiphoid process. The manubrium is the longest sternebra. It projects cranially in front of the first ribs, at the level of the shoulder joint, and is palpable on the ventral midline at the base of the neck.
Only the manubrium is scanned in this model; the rest of the sternum and the costal cartilages are not part of the atlas yet.
Key features
- Cranial end: thickened and slightly flattened, protruding cranially from the thoracic inlet. The sternocephalicus and sternohyoideus muscles attach here.
- Facets for the first costal cartilage: on the lateral surfaces, a little caudal to the cranial end. The first pair of ribs articulates here directly, without an intersternal joint.
- Ventral surface: shows a faint keel, origin of the pectoral muscles.
- Caudal end: joined to the second sternebra by cartilage; the second costal cartilages sit between the two.
Clinical relevance
The manubrium bounds the thoracic inlet ventrally together with the first thoracic vertebra and the first pair of ribs; masses in this region (thymoma, lymphoma, ectopic thyroid) compress the trachea and oesophagus. It is a landmark for median sternotomy and for locating the heart on lateral radiographs. Sternal fractures are rare and usually go with severe thoracic trauma.