Maxilla and ethmoid bone

Maxilla

• The maxilla is a paired bone.

• It is made up from 2 symmetrical bones.

• Each bone consists of a body and 4 processes which includes:

  • Zygomatic

  • Frontal

  • Alveolar

  • Palatine.

The maxilla articulates with 9 bones

• Two bones of the cranium: frontal and ethmoid.

• Seven of the face: the nasal, zygomatic, lacrimal, inferior nasal concha, palatine, vomer, and the adjacent maxillary bone.

The maxilla assists in forming the boundaries of three cavities:

• Roof of the mouth

• The floor and lateral wall of the nasal cavity

• The roof of the mouth

The maxilla participates in the formation of 2 fossae:

1. Infratemporal fossa

2. Pterygopalatine fossa.

Two fissures:

1. The inferior orbital fissure.

2. Pterygomaxillary fissure.

Body of maxilla

It has 4 surfaces:

1. Anterior surface

2. Posterior surface/infratemporal surface

3. Superior/orbital surface

4. Medial nasal surface

Anterior surface

1. Alveolar yokes

2. Incisive fossa

3. Canine fossa

4. Infraorbital foramen

5. Anterior nasal spine

Alveolar yoke

Series of eminences corresponding to the positions of the roots of the teeth.

Incisive fossa

Just above the alveolar yokes of the incisor teeth.

Canine fossa

Lateral to incisive fossa, there is another depression, the canine fossa.

Infraorbital foramen

the end of the infraorbital canal

Anterior nasal spine

At the base of the nasal cavity

Posterior surface/infratemporal surface:

1. Maxillary tuberosity

2. Posterior superior alveolar foramina

Posterior superior alveolar foramina

Content: Posterior superior alveolar nerve, vein and artery

Superior orbital surface

This forms the floor of the orbit:

1. Lacrimal notch- articulates with the lacrimal bone

2. Infraorbital groove, canal and foramen

Infraorbital groove, canal and foramen

The infraorbital groove ends in a canal (infraorbital canal) for the passage of the infraorbotal vessels and nerve.

The infraorbital foramen is below the margin of the orbit.

Medial/nasal surface

This forms the lateral wall of the nasal cavity.

• Opening of the maxillary sinus.

• Nasolacrimal canal

• Conchal crest.

• Broken air cells

Opening of the maxillary sinus

The maxillary sinus opens into the nasal cavity through the maxillary ostium, also known as the maxillary hiatus or maxillary sinus ostium. This opening is located superoposteriorly on the lateral nasal wall

Nasolacrimal canal

Content: Nasolacrimal duct

Conchal crest

For articulation of with the inferior nasal concha

Broken air cells

at the upper border of the nasal surface are some broken air cells which in the articulated skull are closed in the ethmoid and lacrimal bone

Incisive canal

It connects the oral cavity with the nasal cavity.

Content: Nasopalatine nerve, artery and vein.

Ethmoid bone

This is an unpaired bone that creates the nasal cavity.

It is located at the roof of the nose between the two orbits.

The ethmoid bone has 3 parts:

1. Cribiform plate.

2. Ethmoidal labyrinth.

3. Perpendicular plate

Articulation

The ethmoid articulates with 15 bones:

Neurocranium (frontal bone, sphenoid bone).

viscerocranium- 2 nasal bones, two maxillae, 2 lacrimal, 2 palatine bones, 2 inferior nasal conchae and the vomer

Cribiform plate

This articulates with the ethmoidal notch of the frontal bone.

Contents of the ethmoid bone

• Crista galli: dura mater anchors here.

• Foramen Coecum: nasal emissary vein

• Cribiform plate: 22 holes, 11 on each side of the crista galli. The olfactory nerve passes through.

Ethmoidal labyrinth (lateral masses)

Ethmoidal layrinth (lateral masses)

the ethmoidal labyrinth contains the ethmoidal air cell which are arranged in three groups: anterior, middle and posterior which all open into the nasal cavity.

Walls of the ethmoidal labyrinth

superior wall:

Posterior wall:

Lateral wall:

Medial wall:

Superior wall

• broken air cells: this surface presents as number of half-broken cells that are completed in the articulated skull by the frontal bone.

• Anterior and posterior ethmoidal foramen: opens into the inner wall of the orbit.

Posterior wall

Articulates with the body of the sphenoid and orbital process of the palatine bone.

Lateral wall

• Forms the medial wall of the oribit

• Artticulates:

  • superiorly with the orbital plate of the frontal bone.

  • Inferiorly: with the maxilla and orbital process of the palatine bone

  • Anteriorly: with the lacrimal bone

  • Posteriorly: with the body of the sphenoid

Medial wall of the labyrinth

• Forms part of the lateral wall of the nasal cavity.

• It contains:

  • Superior nasal concha

  • Middle nasal concha

The group of ethmoidal air cells

Ethmoidal air cells are also called ethmoid sinuses:

1. Posterior group

2. Middle group

3. Anterior group

Posterior group

Middle group

Anterior group

Perpendicular plate

• It assists in the septum of the nose

• Anterior border:

• Posterior border: