Transcript Osteology of the Face and Skull, Scalp Layers and Jaw
Chris Evans
Understand basic osteology of the skull with attention to the facial skeleton Interpret x-rays of the facial skeleton Explain the movements of the temperomandibular joint Describe the layers of the scalp
Understand the osteology of the skull with attention to the facial skeleton Interpret x-rays of the facial skeleton Explain the movements of the temperomandibular joint Describe the layers of the scalp
◦ ◦ ◦ 22 bones join to form the skull 8 pairs and 6 individuals Divided into neurocranium and viscerocranium Sometimes sutural bones present o Bones of the cranium join together at sutures – immobile fibrous joints with a small degree of elasticity Mandible joins to temporal bone via the synovial temperomandibular joint
The neurocranium covers the brain Split into the cranial base (supports brain) and the calvaria (dome like protective roof) The viscerocranium comprises the facial bones
Neurocranium consists of frontal bone, ethmoid, sphenoid, temporal bone x2, parietal bone x2 and the occipital bone.
Calveria - Upper domed part of cranium which forms the roof of the cranial cavity
Nuchal lines points of attachment for scalp, neck muscles and ligamentum nuchae External occipital protuberance Superior nuchal line
Cranial base supports the brain Split into anterior, middle and posterior sections
Note anterior position of sphenoid Occipital and temporal bones extend far underneath cranial cavity
Consists of mandible, ethmoid, vomer, maxilla x2, inferior nasal concha x2, zygomatic x2, palatine x2, nasal Inferior nasal concha x2 and lacrimal x2 Glabella Nasion Sphenoid bone Ethmoid bone Maxilla Superior orbital margin Nasal bone Lacrimal bone Zygomatic bone Vomer Mandible
Zygomatic bone and temporal bone form zygomatic arch (cheekbone) Zygomatic bone Squamous part of temporal bone Mastoid process Tympanic part of temporal bone Styloid process Temporal process of zygomatic bone Zygomatic process of temporal bone
Contributes to the hard palate (roof of oral cavity)
At birth, the bregma and lambda are missing, as the sutures are not fully formed This leaves soft spots in the skull - fontanelles Squamous suture Bregma Lambda
Pterion – ‘H’ shaped junction formed by the frontal, parietal, sphenoid and temporal bones The bone here is thin, and overlies the anterior branch of middle meningeal artery Trauma here can tear the artery, resulting in life threatening haematoma
Understand the osteology of the skull with attention to the facial skeleton Interpret x-rays of the facial skeleton Explain the movements of the temperomandibular joint Describe the layers of the scalp
Understand the osteology of the skull with attention to the facial skeleton Interpret x-rays of the facial skeleton Explain the movements of the temperomandibular joint Describe the layers of the scalp
Condylar process consists of head and neck of mandible Masseter attachment Head of mandible forms temperomandibular joint with articular tubercle of temporal bone Lateral pterygoid attachment Medial pterygoid attachment Temporalis attachment
Mylohyoid attachment Geniohyoid attachment Digastric attachment
The temporal fossa on the lateral cranium is filled by the temporalis muscle The infratemporal fossa is medial to the ramus of the mandible and lateral to the lateral pterygoid plate, and contains the pterygoid muscles The two fossae communicate by the space medial to the zygomatic arch
Route of communication between temporal and infratemporal fossae Lateral plate of pterygoid process of sphenoid bone
Temperomandibular joint allows opening and closing of mouth and side to side movements Synovial joint is unusual – joint is divided by an articular disk
◦ Masseter – main muscle for chewing Zygomatic arch to lateral surface of ramus of mandible ◦ Temporalis – accessory muscle for chewing, retracts mandible Temporal fossa to coronoid process and anterior margin of ramus
◦ ◦ ◦ Medial pterygoids Deep head from medial surface of lateral pterygoid plate Superficial head from maxilla elevate mandible and perform side to side movements
◦ ◦ ◦ Lateral pterygoids Upper head from roof of infratemporal fossa (sphenoid) to neck of manible Lower head from lateral surface of lateral pterygoid plate Protrude mandible and perform side to side movements
Digastric – anterior belly from digastric fossa on mandible to hyoid, posterior belly from mastoid process to hyoid ◦ Depresses mandible Mylohyoid – mylohyoid line on mandible to hyoid bone ◦ Depresses mandible, supports floor of oral cavity Geniohyoid – inferior mental spine on mandible to hyoid bone ◦ Depresses mandible
When pterygoids on only one side contract, the mandible moves to the opposite side
Understand the osteology of the skull with attention to the facial skeleton Interpret x-rays of the facial skeleton Explain the movements of the temperomandibular joint Describe the layers of the scalp
Covers the neurocranium from superior nuchal line posteriorally to supra orbital margin anteriorally Laterally extends to the zygomatic arches Aponeurotic layer serves as attachemnt point for occipitofrontalis
Top 3 layers form a single unit – the ‘scalp proper’, which moves freely over the loose connective tissue Loose connective tissue layer ‘danger area’ as blood and pus can move easily through it – infection can spread into cranial cavity through emissary veins
S kin contains many sebaceous glands and hair follicles C onnective tissue (dense) contains nerve and blood vessel supply to scalp A poneurotic layer serves as the attachment point for occipitofrontalis muscle bellies L oose connective tissue allows free movement of the scalp proper, possible infection site P ericranium is attached firmly to the calveria, continuous with fibrous tissue in sutures
A Sagittal section P Skin Aponeurosis Bone Frontal belly of occipitofrontalis inserts into skin around eyebrows. Infection can consequently spread to eyes and nose from scalp – ‘black eyes’ Occipital belly of occipitofrontalis inserts into the occipital bone- infection cannot spread down the neck
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