Osteology of the head and neck

This lesson is made to provide the key elements to remember when learning the bones of the head and neck.

Additional Information:

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Overview

Function: Enclose, protect and support e.g. brain and specialised organs. Allows network of pathways for vessels and nerves.

The skull consists of 22 bones (excluding the ossicles)

8 paired = Maxilla, Palatine, Zygomatic, Inferior concha, Nasal, Lacrimal, Parietal and Temporal

6 unpaired = Mandible, Vomer, Ethmoidal, frontal, Occipital, Sphenoid

Bones developed by endochondral ossification: Ethmoid, inf nasal concha, sphenoid, occipital (below the sup. nuchal line) and the petromastoid and styloid parts of the temporal bone. All other bones are formed via intramembranous ossification.

These bones articulate via fibrous joints called sutures (wormian bones)

Skull = with mandible, Cranium = without

Cavities of the skull: cranial, nasal, and orbital.

The skull is made up of the neurocranium and the viscerocranium

Neuroncranium: protects the five special senses and the brain i.e. the cranial vault (calvaria), base, cavity and acoustic skeleton (tympanic cavity, malleus, incus and stapes).

Viscerocranium: related to the digestive and respiratory systems i.e the facial skeleton. Consists of 14 bones.

Cranial cavity:
- Anterior: Houses the frontal lobe of brain.
  Bones: Fontal, ethmoid and lesser wing of sphenoid
  Note: Crista galli, Cribriform plate, Foramen caecum.
- Middle: Hypothalamus, pituitary and temporal lobe
  Bones:Greater and lesser wing + body of sphenoid, petrous part of temporal.
  Note: Sella turcica, Foramen lacerum, Superior orbital fissure, foramen: rotundum, ovale and spinosum.
- Posterior:Cerebellum, pons and medulla oblongata
  Bones: Occipital, body of sphenoid, petrous and mastoid parts of temporal
  Note: Foramen: magnum and jugular, hypoglossal canal, internal acoustic meatus,

Key Sutures

Coronal - Frontal and Parietal bones
Sagittal - Parietal bones
Lambdoid - Parietal, Occipital and Temporal bones.
Squamousal - Temporal and Parietal bones
Sphenosquamous - Temporal and Sphenoid bone

Child fontanelle:
- Anterior
- Anterolateral (sphenoidal)
- Posterior
- Posterolateral (mastoid)

Anatomical points

Bregma: Anterior 'Y' junction - the point where the sagittal and coronal sutures meet

Lambda: Posterior 'Y' junction - the point where the sagittal and lambdoid sutures meet

Pterion: H shape - the thinnest part of the skull where the parietal, frontal, temporal and sphenoid bone articulate (the "Temple" area)

Asterion: junction where the parietomastoid and occipitomastoid sutures meet.

Metopic: This suture isn't normally seen on the adult skull. The frontal bone was once two separate bones until fully fused. (Note: think area of the Nasion)

Bones - Key Features

Bone	Articulates	Landmarks	Foramina, boney pathways + Constituents
Parietal	Frontal Parietal Temporal Occipital Sphenoid	superior and inferior temporal lines part of the temporal fossa parietal foramen meningeal grooves granula foveolae superior sagital groove	Parietal foramen: Emissary vein
Frontal	Parietal Sphenoid Zygomatic Maxilla Ethmoid Nasal Lacrimal	Supra-orbital notch Glabella Frontal sinus Frontal crest superior sagittal groove menigmaal grooves Foramen caecum orbital roof	Foramen Caecum: emissary v. Supra-orbital notch: CN- V1 - Supra-orbital n
Occipital	Parietal Temporal Sphenoid Atlas (C1)	Condyles Clivus - note: basilar part Sinus grooves: inf petrosal transverse occipital sup sagittal meningeal grooves internal and external protuberances Inf and Sup nuchal lines hypoglossal canal condylar canal external occipital crest	F. Magnum: Vertebral a. Meninges Medulla oblongata CN-XI - spinal root Hypoglossal canal: CN-XII - Hypoglassal Jugular foramen: (note: between the temporal and occipital bone) CN-IX - Glossopharyngeal CN-X - Vagus CN-XI - Accessory Sinuses: infer petrosal and sigmoid note: Internal jugular v. Posterior meningeal a. Mastoid foramen (note between temporal and occipital - inconstant) emissary v. and posterior meningeal a. Condylar canal: emissary v and meningeal b of pharyngeal a.
Sphenoid	Frontal Parietal Occipital Temporal Maxilla Zygomatic Ethmoid Palatine Vomer	Wings: Lesser Greater Anterior clinoid process meningeal grooves Body Sella turcica Tuberculum Hypophyseal Dorsum posterior clinoid process Carotid groove Clivus (basilar part of occipital) Pterygoid plates: Later Medial Hamulus Spine Sphenoid sinus	Optic Canal: CN-II - Optic nerve Opthalmic a. Sympathetic plexus SOF: CN-III: oculomotor CN-V1: ophthalmic divi Lacrimal Frontal Nasocillary CN-IV: Trochlear CN-VI: Abducent Superior opthalmic v. IOF: (note: formed between sphenoid and zygomatic) Inf orbital v. Inf orbital a. CN-V2 - Inf orbital n. F. Spinosum Middle meningeal a. & v. F. Rotundum CN-V2 - Maxillary div F. Ovale CN-V3 - Mandibular div. (Note: lesser petrosal n.) F. Lacerum: (note: formed between the sphenoid and temporal bone) pathway of the - internal carotid a. Note: greater petrosal n. Sphenopalatine foramen: CN-V2 - nasopalatine and Posterior sup nasal
Ethmoid	Inf cocha Frontal Sphenoid Palatine Maxilla Vomer Nasal Lacrimal	Orbital plate Perpendicular plate (bone part of nasal septum) nasal concha: Superior middle Crista galli Cribriform plate	Foramen: Ant ethmoidal: Ant Ethmoidal a/v CN-V1 - Ant Ethmoidal Post ethmoidal: Post Ethmoidal a/v CN-V1 - Post Ethmoidal Cribriform foramina: CN-I - Olfactory n.
Lacrimal	Ethmoid Frontal Maxilla Inf concha
Temporal	Parietal Occipital Zygomatic Sphenoid Mandible	Squamous part Petrous part Mastoid process Styloid process Zygomatic process Tympanic part - EAM - IAM Houses vestibular and Cochlear apparatus Mandibular fossa (Glenoid fossa) Articulating eminence Jugular fossa Grooves for the sigmoid and superior petrosal sinuses	Carotid canal: internal carotid a. Internal carotid autonomic nerve plexus Hiatus: lesser and greater petrosal n. IAM: CN-VII - Facial CN-VIII - Vestibular cochlear Labyrinth a. Canaliculus: Tympanic: CN-IX - Tympanic b. of glossopharyngeal n. Mastoid CN-X - Auricular b. of Vagus n. Stylomastoid foramen: CN-VII - Facial Petrotympanic fissure: CN-VII - Chorda tympani (intermediate b) Note: foramen lacerum (see sphenoid bone) Note: mastoid foramen (see occipital bone)
Maxilla	Frontal Sphenoid Zygomatic Maxilla Ethmoid Palatine Vomer Nasal Lacrimal Inf Concha	Processes: Zygomatic Frontal Palatine Maxillary Alveolar Anterior nasal spine Infra-orbital foramen Orbital surface infra-orbital groove (note: IOF) fossa of the lacrimal sac Tuberosity Nasal surface Palatal surface (when together - inter maxillary suture)	Infra-orbital foramen CN-V2 - Infraorbital Alveolar foramina CN-V2 - Alveolar branches. Incisive canal CN - V2 - Nasopalatine Sphenopalatine vessels
Palatine	Sphenoid Maxilla Ethmoid Vomer Palatine Inf concha	Pyramidal process Orbital process Horizontal plate Perpendicular plate Posterior nasal spine Greater and lesser palatine foramina	Foramina: Greater: CN-V2 - greater palatine nerve Lesser: CN-V2 - lesser palatine nerve Note: also vessels
Nasal	Nasal Frontal Maxilla
Vomer	Sphenoid Palatine Maxilla Ethmoid
Inf concha	Ethmoid Maxilla Palatine Lacrimal
Zygomatic	Maxilla Frontal Temporal	Processess: Frontal Temporal Orbital surface	Zygomaticofacial foramen CN-V2 - Zygomaticofacial
Mandible	Temporal (TMJ)	Body: Regions: Base Alveolar mental protuberance Mental formanen Mylohyoid ridge/ line Submandibular fossa Sublingual fossa Ramus: Processes: Coronoid Condylar Angle Mandibular notch Mandibular foramen Lingula Mylohyoid groove (begins)	Mental foramen: CN-V3 - Mental n Mandibular foramen: CN-V3 - Inferior alveolar Mylohyoid groove: CN-V3 - Mylohyoid n and vessel pathway

Key Fossa:

Infratemporal fossa:

One of the most complex anatomical areas of the head and neck. Contains:

Pterygoid venous plexu,
Middle meningeal artier,
Maxillary artery
Otic ganglion
Mandibular Nerve (Trigeminal)
Facial nerve
Internal and external carotid arteries
Internal jugular vein
Initial extra-cranial courses of the glossopharyngeal and hypoglossal.
Pterygoid muscles
Parotid gland
Communicates: Temporal fossa, Pterygopalatine fossa, parapharyngeal spaces, cranium (note: cavernous sinus) and orbit.

Pterygopalatine fossa:

Communications: F rotundum, Pterygoid canal, Inferior orbital fissure, Shpenopalatine foramen, pterygopalatine canal and ptergomaxillary fissure. Therefore communicates with the middle cranial fossa, orbit, nasal cavity and nasal pharynx, Infratemporal fossa and the palate.
It has a venous plexus and contains arteries e.g. maxillary, pterygoid, sphenopalatine and infraorbital a.
Nerves: Maxillary nerve (Trigeminal), pterygoid nerve (Vidian).
Pterygopalatine ganglion.

Osteology overview of the neck

Bones:

Cervical vertebrae: C1-7
Atypical: C1, C2, C7(vertebra prominens = largest)
C1: Atlas
C2: Axis
C3 - level of hyoid bone
C4(and 5) - level of thyroid cartilage, birfurcation of common carotid
C5 - level of carotid pulse, anterior to the Sternocleidomastoid muscle.
C6 - level of larynx and trachea junction, cricoid cartilage (lower border)
C7 - Vertebra prominens and articulates with T1

Typical cervical vertebrae:

Vertebral column - triangular in shape
Bifid spinous process
Bodies - rectangular
Transverse processes - anterior and posterior tubercles)
Unicate processes
Superior and inferior facets
superior and inferior articular processes
Foramen transversarium

Atlas:

No body
No spinous process
Note: No articular discs above or below
Small anterior arch
Articulates with the occipital condyles
Concave and elongated superior facets
Articulating facets for Dens of C2 (Axis)
(nodding joint e.g. Yes-Yes)

Axis:

Dens (the pivot point, may also be referred to as the odontoid process))
Dens - anterior and posterior facets (articulates with Atlas and transverse ligament)
(rotational joint e.g. No-No)