Overview
The cat has thirteen pairs of ribs (costae), one for each thoracic vertebra. Each rib has a dorsal bony part and a ventral costal cartilage. The first nine pairs are sternal (true) ribs: their cartilage articulates directly with the sternum. The last four are asternal (false) ribs: the cartilages of pairs 10 to 12 join the cartilage in front and form the costal arch, and pair 13 ends freely in the muscles as a floating rib.
Key features
- Head (caput costae): articulates with the costal foveae of two consecutive vertebrae.
- Neck and tubercle: the tubercle articulates with the transverse process of the vertebra of the same number; in the last ribs head and tubercle come close together.
- Body: long, curved and narrow; the intercostal vein, artery and nerve run along its caudal border.
- Angle: point of greatest curvature, where the rib changes direction.
- Costochondral junction: between the bony part and the cartilage, palpable in the live cat.
- Costal cartilages: long and flexible; they make the rib cage of the young cat very elastic.
Clinical relevance
- Flail chest: fractures of several consecutive ribs in two places, typically from dog bites or road accidents; the free segment moves paradoxically during breathing.
- Pectus excavatum and flat-chested kitten syndrome: chest wall deformities of kittens that flatten the thorax dorsoventrally and can impair breathing; Burmese cats are overrepresented in the latter.
- Thoracocentesis: performed in the ventral third of intercostal spaces 7–8, at the cranial border of the rib to avoid the intercostal vessels.
- Radiography: counting ribs helps to locate vertebral lesions and to assess heart size (number of intercostal spaces it spans).