The sphenoid sinuses are extensions of the ethmoid sinuses into the sphenoid bones. Articulates with ethmoid bone anteriorly and basilar part of occipital bone posteriorly. The ethmoid sinuses are supplied by anterior and posterior ethmoid branches of the nasociliary nerve. Sinus development begins in the womb, the maxillary and ethmoid sinuses are present at birth. The ethmoid sinuses appear in the fetal fifth month as invaginations of the middle meatus. The ethmoid has three parts&colon; cribriform plate, ethmoidal labyrinth, and perpendicular plate. The ethmoid bone is an anterior cranial bone located between the eyes. The bone found in superior nasal concha is part of the ethmoid bone. The sphenopalatine artery and the ethmoid arteries supply the outer walls of the nasal cavity. Coelacanth also possess a unique rostral organ within the ethmoid region of the braincase. An ethmoid fracture can also sever the olfactory nerve. The ethmoid fracture can produce bone fragments that penetrate the cribriform plate. The porous fragile nature of the ethmoid bone makes it particularly susceptible to fractures. The ethmoid is usually fractured from an upward force to the nose.