Skull, TMJ and Cervical Spine

What does the skull house?

Houses the brain, organs of special sense, upper part of respiratory & gastrointestinal system

The structure of the skull doesn't leave any room for...

The brain to grow

Oedema in the skull can cause

Raised intra-cranial pressure once the sutures in the skull have fused

What is the function of the skull?

• Protects the brain, brainstem, cranial nerves & vasculature

• Provides attachment for muscles

• Provides a framework for the head

• Gives us our identity as individuals

What types of bones are found in the skull?

Flat & irregular bones

Pneumatised bones

What are pneumatised bones?

Bones with air spaces (air cells or sinuses) such as the frontal, temporal, sphenoid & ethmoid

What is the function of pneumatised bones in the skull

Serve 2 functions in the skull; to reduce weight & add resonance to our voice

How do flat bones form

intramembranous ossification

How do pneumatised bones form

endochondral ossification

How many divisions does the skull have?

2

What are the divisions of the skull

Neurocranium and viscerocranium

How many bones are present in the skull?

22 bones in the adult excluding the ossicles of the ear (28 with ossicles)

What is the neurocranium?

Bony case of the brain including cranial meninges with a dome-like roof (calvaria/skullcap) & a floor (cranial base/basicranium)

What is the viscerocranium?

Anterior part of cranium that consists of bones surrounding the oral cavity, nasal cavity & most of the orbit

What bones make up the neurocranium

Frontal

Parietal x2

Occipital

Sphenoid

Temporal x2

Ethmoid

Frontal bone

bone that forms the forehead

Parietal bone

either of two skull bones between the frontal and occipital bones and forming the top and sides of the cranium

Occipital bone

Bone that protrudes at the base of the skull

Sphenoid bone

forms part of the base of the skull and parts of the floor and sides of the orbit

Temporal bone

bone that forms parts of the side of the skull and floor of the cranial activity. There is a right and left temporal bone.

Ethmoid bone

forms part of the posterior portion of the nose, the orbit, and the floor of the cranium

How many bones make up the viscerocranium?

15 irregular bones

What bones make up the viscerocranium

Ethmoid

Palatine x2

Lacrimal x2

Nasal x2

Zygomatic x2

Vomer

Inferior nasal concha x2

Maxilla x2

Mandible

What bone is in both the neuro and viscerocranium

Ethmoid

Palatine bone

either of two irregularly shaped bones that form the back of the hard palate and helps to form the nasal cavity and the floor of the orbits

Lacrimal bone

small fragile bone making up part of the front inner walls of each eye socket and providing room for the passage of the lacrimal ducts

Nasal bone

forms the bridge of the nose

Zygomatic bone

the arch of bone beneath the eye that forms the prominence of the cheek

Vomer bone

Flat, thin bone that forms part of the nasal septum

Inferior nasal conchae

The lowermost scroll-shaped bones on the sidewalls of the nasal cavity.

Maxilla

upper jaw bone

Mandible

lower jaw bone

Which bones of the viscerocranium are singular, midline bones

Ethmoid, vomer and mandible

Which bones of the viscerocranium are paired bones

Palatine

Lacrimal

Nasal

Zygomatic

Inferior nasal concha

Maxilla

On a lateral view, what are the main features of the viscerocranium

Zygomatic arch

Mandible

What forms the zygomatic arch?

temporal process of zygomatic bone and zygomatic process of temporal bone

What is found deep to the mandible

Infratemporal fossa

infratemporal fossa

On a lateral view, what are the main features of the neurocranium

Temporal fossa

External acoustic meatus

Mastoid foramen

Styloid foramen

What is the temporal fossa

The temporal fossa is a depression on the temporal region and one of the largest landmarks on the skull. The temporal bone, the sphenoid bone, the parietal bone and the frontal bone contribute to its concave wall. It is superior to the infratemporal fossa which lies beneath the zygomatic arch.

What is the temporal fossa bound by

Superior and inferior temporal lines superiorly and posteriorly, the zygomatic arch, supramastoid crest, the frontal process of the zygomatic bone and the zygomatic process of the frontal bone

External acoustic meatus

Canal leading to eardrum and middle ear

Mastoid foramen

Styloid foramen

What attaches to the inferior temporal line

temporalis muscle

What attaches to the superior temporal line

temporal fascia

What is the function of the temporalis muscle

Muscle of mastication

Origin and insertion of temporalis muscle

Originates from the temporal fossa. It condenses into a tendon, which inserts onto the coronoid process of the mandible.

What is the pterion?

Junction of frontal, parietal, sphenoid, and temporal bones. H shaped

What artery runs directly behind the pterion?

anterior branch of the middle meningeal artery,

What is significant about the pterion

It is a structurally weak area because the bones are very thin meaning the anterior branch of the middle meningeal artery, that runs directly behind it, is very susceptible to injury if trauma occurs to this area

What can trauma to the anterior branch of the middle meningeal artery cause

An extradural or epidural haematoma

What is the surface landmark of the pterion

4cm superior to midpoint of zygomatic arch & 3cm posterior to frontal process of zygomatic bone

What is the calvarium

The top of the neurocranium

What bones make up the calvaria

frontal, parietal x2, occipital

What sutures fuse the calvarium

Coronal suture

Sagittal suture

Upper part of the lambda suture

What is found in the midline of the calvarium deep to the sagittal suture?

A groove for superior sagittal sinus

What is the superior sagittal sinus?

large vein that carries venous blood to the systemic circulation

What is found on either side of the groove for superior sagittal sinus

Small fossae called granular foveolae

What are granular foveolae?

Arachnoid granulations that return CSF to the venous circulation via the superior sagittal sinus

What suture is found between the 2 parietal bones

Sagittal suture

The squamous part of the occipital bone fuses with the parietal bone via what suture?

Lamboid suture

Describe the surface of the occipital bone

Squamous part is smooth and base is rough

What is the base of the occipital bone also known as?

Nuchal region

What attaches to the nuchal region?

Neck and superficial back muscles

What is the boundary between the squamous and nuchal part of the occipital bone called?

Nuchal line

Superior nuchal line

Inferior nuchal line

What attaches between the superior and inferior nuchal line

Muscles

Name the sutures of the skull

Coronal suture- separates frontal and parietal

Saggital suture- separates the two parietal bones

Lambdoid suture - separates the Parietal, and occipital

Squamous suture

Why at birth are the sutures not fused?

To allow the brain to develop so the skull can accommodate its growth

What type of joint are the sutures?

Structurally, type of fibrous joint

Functionally, limited or no movement (synarthrosis)

What are fontanelles

Unossified areas between the bones that are found during infancy and early childhood. They allow the moulding of the cranial shape during birth and post natal growth of brain

Where is the anterior fontanelle located?

At the junction of the coronal and sagittal suture

When does the anterior fontanelle usually close?

18 months - sometimes will stay

Where is the posterior fontanelle located

Between the sagittal and lamboid suture

When does the posterior fontanelle usually close

6-9 months

What does it mean if the anterior fontanelle is depressed?

Good indicator that the baby is dehydrated or malnourished

What does it mean if the anterior fontanelle is swollen

Increased intracranial pressure

What does a small pulsation in the fontanelle suggest

This is normal - caused by the pressure gradient in the sagittal sinus

What is the piriform aperture?

The anterior opening of the nasal cavity

How many divisions does the trigeminal nerve have

3

What 3 foramina do the divisions of the trigeminal nerve pass through

Ophthalmic (V1) - Supraorbital notch

Maxillary (V2) - Infraorbital foramen

Mandibular (V3) - Mental foramen

Supraorbital notch

Intraorbital foramen

Mental foramen

What is the glabella?

the smooth, raised prominence between the eyebrows just above the bridge of the nose.

What is the nasion?

Junction between nasal bones & frontal bone

What is the orbit?

The bony cavity containing the eyeball

What bones make up the orbit

frontal, sphenoid (greater wing), zygomatic, maxilla, lacrimal, ethmoid, palatine

How does the orbit communicate the rest of the cranial cavity?

Via the superior orbital fissure and the inferior orbital fissure

What is the superior orbital fissure

Connects the orbit to the middle cranial fossa

What does the superior orbital fissure transmit

The nerves supplying the extra ocular muscles - Oculomotor nerve, Abducens nerve and Trochlear nerve - as well as the nerves and vessels supplying structures within the orbit - Lacrimal nerve, Frontal nerve, Nasociliar nerve and Superior ophthalmic vein

What does the inferior orbital fissure transmit

Zygomatic branch of maxillary nerve

Infraorbital nerve

Inferior ophthalmic vein

Sympathetic nerves

What does the inferior orbital fissure connect?

The orbit to the pterygopalatine fossa and from there to the infratemporal fossa

What is a craniometric point?

A landmark on the skull from which craniometric measurements can be taken. An anatomical structure used as a point of origin in locating other anatomical structure (as in surgery) or as a point from which measurements can be taken

Give examples of craniometric points

Pterion

Glabella

Nasion

Bregma

Vertex

Lambda

Inion

Asterion

What is the vertex

highest point of the skull

What is the bregma?

The site on the skull where the coronal suture and the sagital sutures meet....site of the anterior fontanelle.

What is the lambda

junction of sagittal and lambdoidal sutures - site of fusion of posterior fontanelle