lateral mass

The ethmoid bone, an unpaired midline structure, is a critical component of the central skull, contributing to the nasal cavity, orbits, and anterior cranial fossa. This anatomical illustration highlights its key features, including the crista galli, perpendicular plate, cribriform plates, nasal conchae, and ethmoid air cells, showcasing its role in olfaction and structural support. Positioned between the nasal cavity and the brain, the ethmoid bone integrates with surrounding bones to facilitate respiratory and sensory functions.

The atlas (C1) vertebra represents a unique anatomical structure, distinctly different from all other vertebrae in the spinal column. As the first cervical vertebra, it supports the skull and enables precise head movements through its specialized architecture. This ring-shaped vertebra lacks a body and spinous process, instead featuring distinctive lateral masses and arches that facilitate its crucial role in head mobility and stability.