Rib - 9
Costa - IX
Definition
The ninth rib varies among species:
In dogs and cats, it is still sternal, meaning it articulates directly with the sternum through its costal cartilage. It contributes to the middle portion of the thorax.
In horses, cattle, and pigs, the ninth rib is asternal; its cartilage does not connect directly to the sternum but joins that of the preceding rib, forming part of the costal arch. It contributes to the caudal portion of the thoracic cage and serves as an attachment site for the intercostal and abdominal muscles.
The ninth rib marks the transition between the sternal and asternal ribs in most domestic mammals.
References
Barone R. Anatomie comparée des mammifères domestiques, Tome 1, Ostéologie, 5th edition, Vigot, Paris, 2017.
International Committee on Veterinary Gross Anatomical Nomenclature. 2017. Nomina Anatomica Veterinaria. Sixth Edition. Ghent (Belgium).
