There are seven cervical vertebrae in almost all mammals, irrespective of the length of the neck (e.g. in the mouse and the giraffe), which emphasizes their common origin. In the thoracic segment, in contrast, the number of vertebrae ranges from nine to 24 in accordance with the number of the remaining ribs. Man has 12 ribs, though their number may vary from 11 to 13. The number of the lumbar vertebrae varies greatly in animals (from two to nine), while in man there are four to six, usually five, depending on the extent of fusion with the sacrum. ICD 10 Coding will teach all these for the coding and billing.