the breast-bone; a long bone or series of bones, occurring in most vertebrates except snakes and fishes, extending along the middle line of the front or ventral aspect of the trunk, usually articulati, lame, paaritu luu; rinnak ja roided on rinna luuliseks aluseks; rinnak koosneb 3 osast: rinnakupide, rinnakukeha ja mõõkjätke