Overview
The sternum (sternum) forms the floor of the rib cage. It is made up of a series of sternebrae joined by cartilage, which ossify only partly with age. In the horse it is shaped like a boat's keel: compressed laterally in its cranial part, with a prominent ventral crest, and flattened dorsoventrally in its caudal part, where it widens.
Key features
- Manubrium (manubrium sterni): the first sternebra, extended cranially by the manubrial cartilage (cartilago manubrii), which projects between the pectoral muscles and is palpable at the point of the breast.
- Sternal crest: a cartilaginous ventral edge running along the cranial part of the bone, giving attachment to the pectoral muscles.
- Body (corpus sterni): formed by the middle sternebrae; on its sides, the costal notches receive the cartilages of the sternal ribs.
- Xiphoid process and xiphoid cartilage: the caudal end, broad and spade-shaped; it gives attachment to the diaphragm and the linea alba.
Clinical relevance
- Bone marrow aspiration: the sternebrae, on the ventral midline between the thoracic limbs, are a usual site for collecting bone marrow in the adult horse.
- Pectoral abscesses: in the region ventral to the sternum, infection with Corynebacterium pseudotuberculosis produces large abscesses in the pectoral muscles.
- Traumatic injuries: the sternum and its cartilages can be injured in horses that hit fences or obstacles with their chest.