ETHMOID BONE ANATOMY
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What is the ethmoid bone?
- Unpaired cuboid-shaped bone
- Located between your orbital cavities
- Functions:
- Forms part of your anterior cranial fossa
- Contributes to your nasal cavity structure
- Participates in the medial orbital wall
Articulations
Ethmoid Bone - Articulations, Preview from the app. Download 3D OSTEOLOGY for full 3D control—multiple views, x-ray mode, and unlimited zoom.
What does the ethmoid bone articulate with?
- Frontal bone
- Sphenoid bone
- Vomer
- Inferior nasal conchae
- Palatine bones
- Lacrimal bones
- Nasal bones
- Maxillae
STRUCTURAL COMPONENTS
What are the main parts of the ethmoid bone?
- Composed of four main parts:
- Cribriform plate
- Perpendicular plate
- Two ethmoidal labyrinths
- Lightweight yet structurally robust
CRIBRIFORM PLATE
Cribriform Plate, Preview from the app. Download 3D OSTEOLOGY for full 3D control—multiple views, x-ray mode, and unlimited zoom.
What is the cribriform plate?
- Horizontal portion of the ethmoid bone
- Occupies the ethmoidal notch of the frontal bone
- Features a deeply grooved surface
- Provides support for your olfactory bulb
Cribriform Foramina
What are the cribriform foramina?
- Numerous small perforations
- Allow passage of olfactory nerve fibers
- Connect your nasal cavity to your brain
- Enable your sense of smell
Crista Galli
What is the crista galli?
- Vertical bony projection
- Arises from the midline of the cribriform plate
- Serves as attachment for the falx cerebri
- Falx cerebri separates your cerebral hemispheres
Ala of Crista Galli
What is the ala of crista galli?
- Paired extensions
- Flank the anterior border of crista galli
- Articulate with the frontal bone
- Provide additional stability to the ethmoid
PERPENDICULAR PLATE
Perpendicular Plate, Preview from the app. Download 3D OSTEOLOGY for full 3D control—multiple views, x-ray mode, and unlimited zoom.
What is the perpendicular plate?
- Thin vertical bony lamina
- Descends from the inferior surface of cribriform plate
- Forms the superior portion of your nasal septum
- Divides your nasal cavity into left and right halves
- Articulations:
- Inferiorly with the vomer
- Anteriorly with the septal cartilage
- Functions:
- Supports your nasal structure
- Contributes to proper airflow through your nasal passages
ETHMOIDAL LABYRINTH
Ethmoidal Labyrinth, Preview from the app. Download 3D OSTEOLOGY for full 3D control—multiple views, x-ray mode, and unlimited zoom.
What is the ethmoidal labyrinth?
- Two lateral masses flanking the perpendicular plate
- Composed of thin-walled air-filled cavities
- Contains ethmoidal cells (ethmoidal sinuses)
Ethmoidal Cells
What are the ethmoidal cells?
- Grouped into three categories:
- Anterior Cells:
- Located at the front of the labyrinth
- Covered by the lacrimal bone
- Middle Cells:
- Situated between anterior and posterior groups
- Covered by the orbital plate of ethmoid
- Contribute to the medial orbital wall
- Posterior Cells:
- Located at the back of the labyrinth
- Covered by the orbital plate
Orbital Plate
Orbital Plate (Lamina Papyracea), Preview from the app. Download 3D OSTEOLOGY for full 3D control—multiple views, x-ray mode, and unlimited zoom.
What is the orbital plate?
- Thin smooth bony sheet
- Covers middle and posterior ethmoidal cells
- Forms significant portion of your medial orbital wall
Ethmoidal Bulla
What is the ethmoidal bulla?
- Prominent rounded elevation
- Formed by the middle ethmoidal cells
Uncinate Process
What is the uncinate process?
- Curved lamina
- Located anterior to the ethmoidal bulla
- Descends posteroinferiorly
- Articulates with ethmoidal process of inferior nasal concha
Semilunar Hiatus
What is the semilunar hiatus?
- Crescent-shaped groove
- Located between uncinate process and ethmoidal bulla
- Leads into the ethmoidal infundibulum
Ethmoidal Infundibulum
What is the ethmoidal infundibulum?
- Connecting passage
- Opens into the middle nasal meatus
- Facilitates drainage of your frontal sinus
- Facilitates drainage of your maxillary sinus
NASAL CONCHAE
Nasal Conchae, Preview from the app. Download 3D OSTEOLOGY for full 3D control—multiple views, x-ray mode, and unlimited zoom.
Superior Nasal Concha
What is the superior nasal concha?
- Thin curved bony plate
- Extends from medial surface of ethmoidal labyrinth
- Smallest and most superior concha
- Forms upper boundary of superior nasal meatus
Middle Nasal Concha
What is the middle nasal concha?
- Thin curved bony plate
- Extends from medial surface of ethmoidal labyrinth
- Larger than the superior concha
- Projects from the inferior border of the labyrinth
- Forms part of your lateral nasal cavity wall
Functions of Conchae
What do the nasal conchae do?
- Increase surface area within your nasal passages
- Enhance warming of the air you inhale
- Promote humidification of the air you inhale
- Improve filtration of the air you inhale
BIBLIOGRAPHY
1. Henry G, Warren HL. Osteology. In: Anatomy of the Human Body. 20th ed. Philadelphia: Lea & Febiger; 1918. p. 129–97.