The ethmoid bone is a small, complex cranial bone located between the eyes, anterior to the sphenoid bone and posterior to the nasal bones. It plays a central role in the structure of the face and the skull, particularly in the nasal and orbital regions. Here are some key features and information about the ethmoid bone:
- Perpendicular Plate: The perpendicular plate is a thin, vertical portion of the ethmoid bone that projects downward into the nasal cavity. It forms the upper part of the nasal septum, which divides the nasal cavity into left and right sides.
2. Cribriform Plate: The cribriform plate is a horizontal portion of the ethmoid bone located superior to the perpendicular plate. It is characterized by numerous tiny perforations (olfactory foramina) through which the olfactory nerves pass. These nerves are responsible for the sense of smell.
3. Crista Galli: The crista galli is a vertical projection that extends superiorly from the cribriform plate. It serves as an attachment point for the falx cerebri, a fold of the dura mater that separates the two cerebral hemispheres.
4. Ethmoid Labyrinth: The ethmoid bone has two ethmoid labyrinths, one on each side. These are located on the lateral aspects of the perpendicular plate and cribriform plate. The ethmoid labyrinths consist of thin, scroll-like bony structures called ethmoidal conchae (superior and middle) or turbinates. They increase the surface area within the nasal cavity and help humidify and filter inhaled air.
5. Superior and Middle Nasal Conchae (Turbinates): These structures within the ethmoid labyrinths are important for airflow and the functions of the nasal cavity, including filtering and moistening inspired air.
6. Ethmoid Sinuses: The ethmoid bone contains numerous small air-filled cavities known as ethmoid sinuses, which are interconnected with the nasal cavity. These sinuses are part of the paranasal sinus system and help to reduce the weight of the skull and shape the face.
The ethmoid bone is a crucial component of the facial skeleton, contributing to the structure of the nose and the orbits (eye sockets). Its perforated cribriform plate and olfactory foramina are essential for the sense of smell. Additionally, the ethmoid sinuses are important for respiration and are subject to sinus-related issues, such as sinusitis, when inflamed or infected.