ANATOMY

Detailed explanation-1: -They are primarily spongy bone that is covered with a thin layer of compact bone . The vertebrae and some of the bones in the skull are irregular bones .

Detailed explanation-2: -Irregular bones in human skeleton. (shown in red). The irregular bones are: the vertebrae, sacrum, coccyx, temporal, sphenoid, ethmoid, zygomatic, maxilla, mandible, palatine, inferior nasal concha, and hyoid.

Detailed explanation-3: -Irregular bones vary in shape and structure and therefore do not fit into any other category (flat, short, long, or sesamoid). They often have a fairly complex shape, which helps protect internal organs. For example, the vertebrae, irregular bones of the vertebral column, protect the spinal cord.

Detailed explanation-4: -The vertebrae (back bones) of the spine include the cervical spine (C1-C7), thoracic spine (T1-T12), lumbar spine (L1-L5), sacral spine (S1-S5), and the tailbone. Each vertebra is separated by a disc. The vertebrae surround and protect the spinal cord.