The Lateral View of the Skull

Norma Lateralis

The Bones Involved in Norma Lateralis

1. Temporal Bone2. Parietal Bone3. Occipital Bone4. Frontal Bone5. Zygomatic Bone6. Maxilla7. Mandible8. Nasal Bone9. Sphenoid Bone10. Lacrimal Bone.

The Two Divisions of the Skull in Norma Lateralis

1. Cerebral Portion - located above the zygomatic arch.

2. Facial Portion- located below the zygomatic arch.

THE CHARACTERISTIC FEATURES OF THE CEREBRAL PORTION

1. Temporal Lines2. Supramastoid Crest3. Temporal Fossa4. Zygomatico-

temporal foramen5. Zygomatic arch6. Infratemporal fossa7. Suprameatal triangle8. Pterion9. Asterion.

Pterion

- the thinnest part of the lateral wall of the skull.

- an important area because it overlies the anterior division of the middle

meningeal artery and vein.

- point where the posteroinferior angle of the parietal bone meet the occipital bone and the mastoid part of the temporal bone.

Asterion

THE CHARACTERISTIC FEATURES OF THE FACIAL PORTION

1. Zygomatic arch2. Articular tubercle3. External acoustic

meatus4. Mandibular fossa5. Styloid process6. Mastoid temporal7. Mastoid process8. Mastoid foramen9. Gonion.

10. Pterygo-maxillary fissure11.Pterygo-palatine fossa12.Spheno-palatine foramen.

THE TEMPORAL BONE

• 1. Squamous part

• 2. Mastoid part

• 3. Tympanic part

• 4. Petrous part

Four Parts of the Temporal Bone

THE THREE FOSSAE IN NORMA LATERALIS

1. Temporal Fossa

2. Infratemporal Fossa

3. Pterygopalatine Fossa

THE TEMPORAL FOSSA

A flat, fan-shaped depression on the lateral surface of the skull.

Bones involved:1. Zygomatic Bone2. Frontal Bone3. Greater Wings of

Sphenoid4. Temporal Bone5. Parietal Bone

BOUNDARIES OF THE TEMPORAL FOSSA

Boundaries Structure

Superior Inferior Temporal Line

Anterior Frontal Process of Zygomatc Bone

Medial Surface of parietal bone,Temporal Bone, frontal bone and GWS

Lateral Zygomatic ArchInferior Infratemporal Crest of

Sphenoid BonePosterior Inferior Temporal line

1. Temporalis muscle is attached to its floor.

2. Pterion – a small circular area where the frontal, parietal, sphenoid, and temporal bones are close together.

Contents of the Temporal Fossa

THE INFRATEMPORAL FOSSA

- A paired depression that is inferior to anterior part of the temporal fossa.

- Divided from the temporal fossa by the crest of the greater wings of sphenoid.

BOUNDARIES OF THE INFRATEMPORAL FOSSA

Boundaries Structure

Superior Greater wings of sphenoid

Anterior Maxillary tuberosity

Medial Lateral pterygoid plate

Lateral Mandibular ramus and zygomatic arch

Inferior No borderPosterior No border

1. The mandibular division of the trigeminal nerve,

2. Contains pterygoid plexus and the pterygoid muscles,

3. Maxillary artery and its branches, middle meningeal artery,

4. Inferior alveolar artery, 5. Posterior alveolar artery.

Contents of the Infratemporal Fossa

THE PTERYGOPALATINE FOSSA

A cone-shaped depression, deep into the infratemporal fossa.

It is located between the pterygoid process and the maxillary tuberosity near the apex of the orbit.

BOUNDARIES OF THE PTERYGOPALATINE FOSSA

Boundaries Structure

Superior Inferior surface of the body of the sphenoid

Anterior Maxillary tuberosity

Medial Vertical plate of the palatine bone

Boundaries Structure

Lateral Pterygomaxillary fissure

Inferior Pterygopalatine canal

Posterior Pterygoid process of the sphenoid bone

1. Maxillary artery and its branches,

2. Pterygopalatine ganglion,

3. Maxillary nerve.

Contents of the Pterygopalatine Fossa

The Temporomandibular Joint

- is a complex articulation of the movable mandible and the base of the skull.

Articulation takes place in two areas:

1. Between maxillary and mandibular teeth ( interjaw dental occlusion ), and

2. Between the mandibular condyle and the temporal bone.

Bones Involved in the TMJ

1. Condylar process or condyle of the mandible

2. Mandibular fossa3. Articular

emminence of the temporal bone

COMPONENTS OF THE TMJ

1. Articular or Fibrous Capsule

2. Temporo-mandibular (lateral) Ligament

3. Articular Disc

4. Joint Cavities

1. ARTICULAR OR FIBROUS CAPSULE

- encloses the joint surfaces like a sleeve that runs from the temporal bone superiorly, to the condyle of the mandible inferiorly. The enclosed space between the articular surfaces is the joint cavity

Superior attachment :

area surrounding the mandibular fossa and articular eminence of the temporal bone.

Inferior attachment:

periphery of the mandibular condyle.

2. TEMPOROMANDIBULAR (LATERAL) LIGAMENT

- is a lateral thickening of the

joint capsule and is similar to

the collateral ligaments of

other joints.

- It prevents posterior and

inferior displacement of the

condyle but allows limited

anterior movements of the

condyle.

3. ARTICULAR DISC

- it is composed of dense fibrous tissues and lies within the joint

capsule, intervening between the condyle and the mandibular fossa.

- It is a biconcave disc that serves to provide reciprocal articular

surfaces between its inferior surface and the condyle, and its superior

surface and the mandibular fossa and eminence.

Three zones of the articular disc:

1. Posterior thickening – sits atop the condyle and fills the mandibular fossa above when the mandible is at rest.

2. Anterior thickening - lies just below the posterior slope of the articular eminence.

3. Intermediate zone - lies between the two previous zones.

4. JOINT CAVITIES

The disc effectively divides the joint cavity into two distinct upper and

lower compartment that allow two types of joint movements.

These cavities are also filled with synovial fluid which nourishes the

articular disc.

Joint Cavities

ACCESSORY LIGAMENTS

Two accessory ligaments span the joint but do not significantly limit mandibular movements:

1. Sphenomandibular ligament - it runs from the spine of the sphenoid bone to the lingula of the mandible.

2. Stylomandibular ligament- it runs from the styloid process of the temporal bone to the angle of the mandible.

THE SYNOVIAL MEMBRANE

A layer of synovium lines the inner aspects of the joint capsule. This relatively dense membrane does not line the actual articular surfaces of the joints because synovial joints are generally weight-bearing joints.

The pressure in the TMJ is provided by the occluded maxillary and mandibular teeth.

Synovium secretes synovial fluids for lubrication and nourishment of the opposing articular surfaces.

1. An intimal cellular layer- contains type A cells which are phagocytic, and type B cells which synthesize hyaluronate found in synovial fluid.

2. A vascular subintimal layer- Contains blood vessels, and lymphatics

within the loose connective tissue matrix.

Two Layers of the Synovial Membrane

NERVE SUPPLY OF THE TMJ

1. Branches of the temporalis N.

2. Branches of the auriculotemporal N.

3. Branches of the masseteric N.

BLOOD SUPPLY OF THE TMJ

1. Superficial temporal artery

2. Muscular branches of the maxillary artery

TEMPOROMANDIBULAR JOINT IN ACTION

MUSCLES ACTING ON THE TMJ

1. Masseter2. Temporalis3. Lateral Pterygoid4. Medial Pterygoid

Protrussion:

1. Lateral pterygoid m.

2. Medial pterygoid m.

Retraction

1. Temporalis M.

Synergists:a. Massetersb. Digastricc. Geniohyoid

Elevation

1. Temporalis2. Masseter 3. Medial

pterygoid

Depression

1. Lateral pterygoid

Synergists:2. Digastric3. Geniohyoid4. Mylohyoid

Lateral movements

1. Medial pterygoid m.

2. Lateral pterygoid m.