Overview
The dog has thirteen pairs of ribs, matching the thirteen thoracic vertebrae. The first nine are sternal (their cartilage reaches the sternum), the last four are asternal (their cartilages join each other forming the costal arch) and the thirteenth is usually floating. Each rib has a dorsal bony part and a ventral costal cartilage, joined at the costochondral junction.
In this model ribs 1, 4, 9 and 13 come from scans of a real dog; the others were interpolated between those four, and the costal cartilages are schematic. The right side mirrors the left.
Key features
- Head (caput costae): articulates with the costal foveae of two adjacent vertebrae (except in the last ribs).
- Neck and tubercle (tuberculum costae): the tubercle articulates with the transverse process of the vertebra of the same number.
- Costal angle: point of greatest curvature, most marked in the middle ribs.
- Body: flattened, with the costal groove on the caudal border carrying the intercostal vessels and nerve.
- First rib: short, wide and almost straight; with T1 and the manubrium it bounds the thoracic inlet.
Clinical relevance
Rib fractures are common after trauma (road accidents) and may come with pneumothorax or pulmonary contusion. The intercostal spaces are the access route for thoracocentesis (7th-8th space) and thoracotomy. The last rib is a landmark for locating the kidney and for body condition scoring.