Skull and Cervical Spine: Anatomy and Imaging Flashcards
Name the main bones of the orbit.
Frontal Lacrimal Ethmoid Maxilla Zygomatic Sphenoid ➡Greater wing Palatine
Identify the structures which pass through the superior orbital fissure.
- Lacrimal nerve
- Frontal nerve
- Trochlear nerve
- Superior ophthalmic vein
- Nasociliar nerve
- Oculomotor nerve
- Abducens nerve
Identify the structures which pass through the inferior orbital fissure.
- Zygomatic branch of maxillary nerve
- Infraorbital nerve
- Inferior ophthalmic vein
- Sympathetic nerves
What is the skull ?
Cranium, bony skeleton of the head, including the mandible
What does the skull contain ?
Houses the brain, organs of special sense, upper part of respiratory and gastrointestinal system
How much movement is possible at the skull ?
Restricted movement only in relation to the mandible at the temporomandibular joint (TMJ, to open and close the mouth) and the atlanto-occipital joint
Identify the main functions of the skull.
- Protects the brain, brainstem, cranial nerves and vasculature
- Provides attachment for muscles
- Provides a framework for the head
- Gives us our identity as individuals
What types of bones make up the skull ?
Flat and irregular bones
Pneumatised bones
Define pneumatised bone, and give examples. What is their function ?
Bones with air spaces (air cells or sinuses) such as the frontal, temporal, sphenoid and ethmoid
Serve 2 functions in the skull; to reduce weight and add resonance to our voice
What is the difference between development and irregular bones ?
- Flat, smooth bones form by intramembranous ossification
* Irregular bones form by endochondral ossification
Identify the main divisions of the skull.
1) Neurocranium: Bony case of the brain including cranial meninges with a dome-like roof (calvaria/skullcap) and a floor (cranial base/basicranium)
2) Viscerocranium: Anterior part of cranium that consists of bones surrounding the oral cavity, nasal cavity and most of the orbit
How many bones does the skull contain ?
22 bones in the adult excluding the ossicles of the ear (28 with ossicles)
Identify the bones of the neurocranium. How many are there in total ?
8 in total
➡ Singular midline bones: Frontal Occipital Sphenoid Ethmoid
➡ Sets of bilateral paired bones:
Parietal x2
Temporal x2
Identify the bones of the viscerocranium. How many are there in total ?
15 irregular bones
➡ Singular midline bones:
Ethmoid
Vomer
Mandible
➡ Sets of bilateral paired bones: Nasal x2 Lacrimal x2 Zygomatic x2 Palatine x2 Maxillae x2 Inferior Nasal Conchae x2
What are the main features of the viscerocranium ?
Zygomatic arch, mandible and infratemporal fossa
What are the main features of the neurocranium ?
External acoustic meatus (opening), styloid and mastoid processes and temporal fossa
Identify the superior, inferior, posterior, anterior borders, and floor of the temporal fossa.
Superior and posterior borders: Superior and inferior temporal lines
Anterior border: Frontal process of zygomatic bone and zygomatic process of frontal bone
Inferior border: Infratemporal crest deep to zygomatic arch
Floor: Includes pterion
What is the pterion ?
- H-shaped junction of sutures
* Frontal, parietal, temporal, and greater wing of sphenoid bone meet here
What is the clinical significance of the pterion ?
Structurally weak (thin) area of the skull. Overlies anterior branch of the middle meningeal artery, so vulnerable, trauma can lead to extradural (epidural) hematoma
Describe the location of the pterion (in surface anatomy).
4cm superior to midpoint of zygomatic arch and 3cm posterior to frontal process of zygomatic bone.
What are the main components of the calvaria ?
4 flat bones (2x parietal, single frontal and occipital) fused by the coronal, sagittal and lambdoid sutures
What is the function of arachnoid granulations ?
Arachnoid granulations return CSF to the venous circulation.
Define Wormian bone.
Sutural, accessory
or Wormian bones, are msall islands of bone which may be seen within a cranial suture (most commonly observed in the lambdoid sutures)
Define suture. How much movement is allowed here ?
- Structurally, type of fibrous joint
* Functionally, limited or no movement (synarthrosis)
Define fontanelle. What is their function ?
“One of the membrane-covered spaces remaining at the junction of the sutures in the incompletely ossified skull of the fetus or infant, that fuse in the post-natal life”. Two of them, anterior and posterior fontanelle
Along with sutures, allow moulding of cranial shape during birth + post-natal growth of brain.
How soon do fontanelles close ?
• Posterior fontanelle closes 2 months post-birth
• Corners of frontal and
parietal bones fuse by 18 months (anterior fontanelle)