 Cats have seven cervical vertebrae , as do almost all mammals ; 13 thoracic vertebrae ( humans have 12 ) ; seven lumbar vertebrae ( humans have five ) ; three sacral vertebrae like most mammals ( humans have five ) ; and a variable number of caudal vertebrae in the tail ( humans retain three to five caudal vertebrae , fused into an internal coccyx ) . The extra lumbar and thoracic vertebrae account for the cat 's spinal mobility and flexibility . Attached to the spine are 13 ribs , the shoulder , and the pelvis . Unlike human arms , cat forelimbs are attached to the shoulder by free @-@ floating clavicle bones which allow them to pass their body through any space into which they can fit their head . 
