Bones - The Skull

Question 1

How many bones make up the cranium?

Answer 1

The cranium is made up of eight bones: Frontal Sphenoid Ethmoid Parietal (x2) Temporal (x2) Occipital

Question 2

What bones make up the calvarium?

Answer 2

Frontal Parietal (x2) Occipital

Question 3

What bones make up the cranial base?

Answer 3

Frontal Sphenoid Parietal (x2) Temporal (x2) Ethmoid Occipital

Question 4

How many bones make up the face?

Answer 4

The face is made up of 14 bones: Mandible - jaw bone. Zygomatic (x2) - forms cheek bones - articulates with the frontal, sphenoid, temporal and maxilla bones. Maxilla (x2) - comprises part of the upper jaw and the hard palate. Lacrimal (x2) - smallest bones of the face. Vomer - forms the posterior aspect of the nasal septum. Inferior nasal conchae (x2) - located within the nasal cavity and increases the amount of surface area of the nasal cavity so that more inspired air can come into contact with the cavity walls. Nasal (x2) - slender bones, located at the bridge of the nose. Palatine (x2) - situated at the rear oral cavity. It forms the posterior of the hard palate.

Question 5

What are the sutures of the cranium? When do they fuse completely?

Answer 5

A fibrous type joint that hold the bones of the cranium together. These fuse completely at around age 20.

Question 6

What are the main sutures?

Answer 6

1) Coronal - hold the frontal and parietal bones together. 2) Lambdoid - hold the occipital and parietal bones together. 3) Sagittal - runs between the coronal and lambdoid suture at the sagittal axis.

Question 7

At the juction between sutures are… What are the clinical significance of these strucutres?

Answer 7

Two fontanelles (anterior and posterior). Sunken fontanelle indicates dehydration. A tense or bulging fontanelle indicates intracranial pressure.

Question 8

Clinical relevance: cranial fractures

Answer 8

Aetiology - blunt or penetrating trauma. Signs and symptoms - visible injuries, CSF leaking from the ears and nose (CSF leak indicative of base of skull fracture), poor balance, confusion, slurred speech and a stiff neck. Points of weaknesses in the skull - 1) The pterion - ‘H-shaped’ junction between temporal, parietal, frontal and sphenoid bones. The thinnest part of the skull. A fracture here can lacerate the middle meningeal artery (anterior branch), resulting in an extradural haematoma. 2) Anterior cranial fossa 3) Middle cranial fossa 4) Posterior cranial fossa Four types of fractures: 1) Depressed - depression of the bone inwards, causing skull indentation. 2) Linear - a simple break traversing its full thickness. They have radiate (stellate) fracture lines away from the point of impact. This is the most common type of cranial fracture. 3) Basal skull - affects the base of the skull. Characterised by brusising behind the ears, known as Battle’s sign (mastoid ecchymosis) or bruising around the eyes/orbits, known as Raccoon eyes. Diastatic - fracture along the suture line, causing widening of the suture. They are most often seen in children.

Question 9

Clinical relevance: facial fractures

Answer 9

Facial fractures are common and trauma-related i.e RTA, fights and falls. They are associated witih clinical features, such as profuse bleeding, swelling, deformity and anaesthesia of the skin. The nasal bones are the most frequently fractured, due to their prominent position at the bridge of the nose. A maxillofacial fracture is one that affects the maxillary bones. This requires a trauma with a large amount of force. Facial fractures affecting the maxillary bone can be identified using the Le Fort classification, depending on the bones involved, ranging from 1 to 3 (most serious).