Session 2 - Osteology of the Skull

Question 1

The skull consists of how many individual bones?

Answer 1

22

Question 2

The bones of the skull can be broadly divided into what two groups?

Answer 2

Neurocranium (calvaria, cranial floor)

Viscerocranium (facial skeleton, jaw)

Question 3

What are the names of the three depressions that form the cranial floor?

Answer 3

Anterior cranial fossa
Middle cranial fossa
Posterior cranial fossa

Question 4

What are the layers in the trilaminar arrangement of the bones of the calvaria?

Answer 4

Outer table (cortical bone)
Diploeic cavity (cancellous bone)
Inner table (cortical bone)

Question 5

What is the benefit of the trilaminar arrangement in bones of the calvaria?

Answer 5

Gives protective strength without adding significant weight

Question 6

What are sutures in the skull?

Answer 6

Fibrous joints found at intersections between the bones of the skull.

Question 7

What are the three main suture lines?

Answer 7

Coronal
Sagittal
Lambdoid

Question 8

What are fontanelles?

Answer 8

Large areas of unossified membranous gaps between flat bones of the calvaria, found in infants.

Question 9

When do anterior and posterior fontanelles fuse?

Answer 9

Anterior: 18 months - 2 years
Posterior: 1-3 months

Question 10

What is craniosyntosis?

Answer 10

Rare condition where there is early fusion of fontanelles and sutures

Question 11

How can the anterior fontanelle be clinically useful when examining new borns and infants?

Answer 11

Inspection and gentle palpation of the anterior fontanelle can be used to assess the intracranial pressure and state of hydration.

Question 12

What are the two main types of skull fracture?

Answer 12

Linear - through the full thickness of the skull, fairly straight, no bone displacement
Depressed - fragment is displaced inwards towards the brain

Question 13

Fractures involving the cranial base are known as what?

Answer 13

Basilar skull fractures

Question 14

What clinical signs indicate a basilar skull fracture?

Answer 14

Cerebrospinal fluid leaks (e.g. from the nose (CSF rhinorrhea) or from the ears (CSF otorrhea))
Raccoon eyes
Battle’s sign (bruising over the mastoid process)
Haemotympanum (blood behind the ear drum)

Question 15

What is the pterion?

Answer 15

The thinnest area of the skull. Relatively easy to fracture.

Question 16

What blood vessel underlies the pterion?

Answer 16

Middle meningeal artery (anterior branch)

Question 17

Bleeding from the middle meningeal artery will result in what kind of haematoma?

Answer 17

Extradural haematoma

Question 18

The large number of foramina found in the cranial floor increase its vulnerability to what?

Answer 18

Fracture, if significant force is transmitted through the skull base

Question 19

What are the different types of intracranial heamatoma?

Answer 19

Epidural/extradural
Subdural
Subarachnoid
Intracerebral

Question 20

What is the only moveable joint of the skull?

Answer 20

Temporomandibular joint (TMJ)

Question 21

Facial fractures most commonly involve which bones?

Answer 21

Nasal bones (because of the prominence of the nose), the zygomatic bone and the mandible.

Question 22

What structures run through the foramen magnum?

Answer 22

Medulla
Meninges
Vertebral arteries
Spinal accessory nerve (ascending)
Duran veins
Anterior and posterior spinal arteries

Question 23

What structures run through the internal acoustic meatus?

Answer 23

Facial nerve (CN VII)
Vestibulocochlear nerve (CN VIII)
Labrynthine artery

Question 24

What structures run through the jugular foramen?

Answer 24

Glossopharyngeal nerve (CN IX)
Vagus nerve (CN X)
Spinal accessory nerve (descending) (CN XI)
Internal jugular vein
Inferior petrosal sinus
Sigmoid sinus
Meningeal branches of the ascending pharyngeal and occipital arteries

Question 25

What structure runs through the hypoglossal canal?

Answer 25

Hypoglossal nerve (CN XII)

Question 26

The crista galli is found in the midline of which bone?

Answer 26

Ethmoid bone

Question 27

What structures run through the cribriform foramina?

Answer 27

Olfactory nerve fibres (CN I)

Question 28

Other than the cribriform foramina, what other two foramina are found in the cribriform plate?

Answer 28

Anterior ethmoidal foramen

Posterior ethmoidal foramen

Question 29

What structures run through the superior orbital fissure?

Answer 29

Oculomotor nerve (CN III)
Trochler nerve (CN IV)
Ophthalmic branch of the trigeminal nerve (CN Va)
Abducens nerve (CN VI)
Ophthalmic veins
Sympathetic fibres

Question 30

What structures run through the optic canals?

Answer 30

Optic nerves (CN II)
Ophthalmic arteries

Question 31

What groove runs transversely between the two optic canals?

Answer 31

Chiasmatic sulcus

Question 32

Foramen rotundum transmits what structure?

Answer 32

The maxillary branch if the trigeminal nerve (CN Vb)

Question 33

Foramen rotundum opens into what fossa?

Answer 33

Pterygopalatine fossa

Question 34

Foramen ovale transmits what structures?

Answer 34

Mandibular branch of the trigeminal nerve (CN Vc)

Accessory meningeal artery

Question 35

Foramen ovale opens into what fossa?

Answer 35

Infratemporal fossa

Question 36

Foramen spinosum transmits what structures?

Answer 36

Middle meningeal artery
Middle meningeal vein
A meningeal branch of CN Vc

Question 37

Foramen spinosum opens into what fossa?

Answer 37

Infratemporal fossa

Question 38

The carotid canal transmits what structures?

Answer 38

Internal carotid artery

Deep petrosal nerve

Question 39

Through which foramina do the different branches of the trigeminal nerve run?

Answer 39

Opthalmic (CN Va) - superior orbital fissure
Maxillary (CN Vb) - foramen rotundum
Mandibular (CN Vc) - foramen ovale

Question 40

Which two foramina provide a connection between the infratemporal fossa and the cranial cavity?

Answer 40

Foramen ovale

Foramen spinosum