The skull 3 of 5 Ethmoid

Ethmoid Bone Overview

• Lightweight and spongy structure, derived from the Greek word "Ethmos," meaning sieve.
• Small, unpaired bone forming part of the orbital complex.
• Located in the paranasal sinuses, contributing to the medial wall of the orbit and the anterior cranial fossa.

Anatomy of Ethmoid Bone

• Composed of four main parts:
  • Cribriform plate: Roof of nasal cavity, perforated by olfactory nerve fibers.
  • Perpendicular plate: Forms the superior two-thirds of the nasal septum; a thin quadrilateral bone.
  • Ethmoid labyrinths: Large masses on either side of the perpendicular plate containing ethmoid air cells (ethmoid sinuses).
• Innervation from anterior and posterior ethmoidal branches impacting the nasal septum and lateral wall.

Ethmoid Labyrinths

• Houses ethmoid air cells, contributing to warming and moistening inspired air, and providing voice resonance.
• Divided into anterior, middle, and posterior clusters for air cell arrangement.

Clinical Relevance

• Bleeding can occur from frequent nose blowing.
• Fracture of the cribriform plate may cause anosmia (loss of smell).
• Inflammation can lead to rhinorrhea (clear watery fluid drainage).
• Ethmoid labyrinth fracture may result in communication between the nasal cavity and orbit, potentially causing orbital emphysema.
• Sinusitis: Inflammation or infection leading to damage in the ethmoid area, often cited with facial trauma or dental infections.

Symptoms and Consequences

• Coughing, sneezing, and blowing the nose may exacerbate inflammation.
• Rhinorrhea may indicate cerebral spinal fluid leakage into the nasal cavity.

Structural Significance

• Ethmoid bone separates the nasal cavity from the cranial cavity.
• Plays an essential role in the structural integrity of the skull and the function of the nasal region.