Fish, frogs, reptiles, birds and mammals are called vertebrates. Their spine helps support the body and head. The rest of the skeleton of all these animals, except the fish, also has the same basic design with a skull that protects the brain and sense organs and ribs that protect the heart and lungs and, in mammals, which allows them to breathe. Each of their four legs is made with the same basic pattern. It is joined to the spine by a flat, broad bone called a girdle and has one long upper bone, two long lower bones, and several smaller bones in the wrist or ankle.
The shape and size of the vertebrae of mammals are different from the neck to the tail. In the neck there are cervical vertebrae with the two top ones, the atlas and axis, meant to support the head and allow it to nod. Their Thoracic vertebrae are in the chest region and have a special surface against where the ribs move during breathing. Grazing animals like cows and giraffes that have to support weighty heads on long necks have extra-large spines on their cervical and thoracic vertebrae for muscles to connect to. Lumbar vertebrae in the loin region are usually large strong vertebrae with prominent spines for the attachment of the large muscles of the lower back. The sacral vertebrae are usually combined into one solid bone called the sacrum that sits within the pelvic girdle. Finally there are a number of small bones in the tail called the coccygeal vertebrae.
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