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Head and Neck Anatomy > Skull Osteology - Cranial Base > Flashcards

Skull Osteology - Cranial Base Flashcards

1
Q

What are the 3 regions (fossa) of the cranium?

A
  1. anterior
    - house for frontal lobes
  2. middle
    - house for temporal lobes
  3. posterior
    - house for occipital lobes, cerebellum and medulla oblongata
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2
Q

The anterior cranial fossa is formed by?

A
  1. Frontal bone (orbital parts)– anteriorly
  2. Ethmoid bone – middle
  3. Sphenoid bone (body and lesser wing) – posteriorly
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3
Q

Describe the surface of the anterior cranial fossa?

A

brain markings of orbital gyri

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4
Q

What does the frontal bone form in the anterior cranial fossa?

A
  1. Frontal crest – median bony extention
  2. Foramen caecum – base
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5
Q

What does the ethmoid bone form in the anterior cranial fossa?

A
  1. Crista galli – median ridge posterior to foramen caecum
  2. Cribriform plate – sieve-like passage for olfactory nerves to olfactory bulb
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6
Q

What does the ethmoid bone contribute to?

A
  1. Perpendicular Plates
  2. Superior & Middle Nasal Concha
  3. Cribriform Plate
  4. Crista Galli
    N.B. the ethmoid bone is the deppest skull bone
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7
Q

Describe a common anterior cranial fossa fracture and subsequent signs + symptoms?

A
  1. Cause
    The cribriform plate may be fractured
  2. Consequence
    - Usually results in tearing of the overlying meninges
  3. Signs and symptoms
    - The patient will have bleeding from the nose and leaking of CSF into the nose (rhinorrhea)
    - Battles sign
    - unequal pupils
    - discoloration of soft tissue under eyes
  4. Potential treatment
    - if any sinus is involved in a fracture antibiotics must be given prophylatically as the sinus renders it a compound fracture even if the skin is intact.
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8
Q

What are Raccoons eyes?

A

Periorbital edema and bruising suggestive of Frontal-basal fracture

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9
Q

What is the middle cranial fossa composed of?

A
  1. Large depressions on each side
  2. Small depression called sella turcica
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10
Q

What are the 3 bony parts that form the middle cranial fossa?

A
  1. Greater wing of sphenoid bone
  2. Squamous part of temporal bone – laterally
  3. Petrous part of temporal bone – posteriorly
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11
Q

What separates the middle and anterior cranial fossae?

A
  1. Sphenoid crest – laterally
  2. Sphenoid limbus – medially
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12
Q

What separates the middle and posterior cranial fossae?

A
  1. Pretrous crest of temporal bones – laterally
  2. Dorsum sellae of sphenoid – medially
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13
Q

What is the function of the middle cranial fossa?

A

Supports temporal lobes of the brain

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14
Q

Describe the sella turcica?

A
  • Surrounded by anterior and posterior clinoid processes
  • Lesser wings of sphenoid overhangs the fossa
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15
Q

The sella turcica is composed of which 3 parts?

A
  1. Tuberculum sella –anteriorly
  2. Hypophysial fossa (pituitary fossa)
  3. Dorsum sellae
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16
Q

Describe the sphenoid bone?

A

A prominent, irregular, wedge-shaped bone at the base of the skull.
Note: The sphenoid bone has been called the “keystone” of the cranial floor since it is in contact with all of the other cranial bones.

17
Q

What are the landmarks of the sphenoid bone?

A
  1. Greater wings: large lateral projections of bone that help to form the lateral border of the skull
  2. Lesser wings: smaller lateral projections of bone above the greater wings
  3. Pterygoid processes: two long downward projections from the greater wings that act as a point of muscle attachment.
  4. Sella turcica: known as the Turkish Saddle which cradles the pituitary gland
18
Q

What are the 5 foramina of the sphenoid bone?

A
  1. Superior orbital fissure
  2. Foramen rotundum
  3. Foramen Ovale
  4. Foramen spinosum
  5. Foramen lacerum
19
Q

Describe the superior orbital fissure and what it transmits?

A
  • between the lesser and greater wings
  • Transmits opthalmic veins and nerves entering the orbit
    > oculomotor nerve CNIII
    > trochlear nerve CNIV
    > ophthalmic CNV1
    > abducens CNVI
    > sympathetic fibers
20
Q

Describe the Foramen rotundum and what it transmits?

A
  • posterior to the medial end of superior orbital fissure.
  • Transmits maxillary nerve (CN V2)
21
Q

Describe the foramen ovale and what it transmits?

A
  • posterolateral to foramen rotundum
  • opens in infratemporal fossa
  • Transmits mandibular nerve (CN V3) and small accessory meningeal artery
22
Q

Describe the foramen spinosum and what it transmits?

A
  • postlateral to foramen ovale
  • Transmits middle meningeal vessels and meningeal branch of mandibular nerve
23
Q

Describe the foramen lacerum and what it transmits?

A
  • artefact of dried skull
  • In life covered by cartilage.
  • Posteriorly and laterally the re is a groove for greater petrosal nerve
24
Q

What is the consequence of fractures to the middle cranial fossa?

A
  1. Consequence
    Otorrhea
  2. Clinical presentation
    - Leakage of blood and CSF from the ear is common in middle cranial fossa fractures .
  3. Treatment
    - Drainage of CSF from the ear
  4. Cause
    - Suggestive of a Fracture of the temporal bone with torn meninges
25
Q

What part of the middle cranial fossa is usually fractured?

A

The base of the skull is more fragile than the vault and is thus commonly involved in fractures

26
Q

What part of the middle cranial fossa is rarely involved in fractures?

A

The petrous part of the temporal bone is rarely involved
> Which fits with it’s name
– petrous = rock like i.e. Strong

27
Q

Describe the posterior cranial fossa and it’s contents?

A
  • Largest and deepest
  • Contains cerebellum, pons and medulla oblongata
28
Q

The posterior cranial fossa is formed by?

A
  1. occipital bone
  2. Dorsum sella of sphenoid – medially
  3. Petrous and mastoid parts of temporal bone –anterolaterally
    Note: Clivius – centrally inclined part of occipital bone
29
Q

Describe the landmarks of the posterior cranial fossa?

A
  • Divided by internal occipital crest into two crebellar fossae
  • Internal occipital fossa ends up in internal occipital protuberance ( confluence of dural venous siunuses
  • Transverse and sigmoid dural venous sinuses – grooves anterolaterally
30
Q

Name the foramina of the posterior cranial fossa?

A
  1. foramen magnum
  2. jugular foramen
  3. hypoglossal canal
  4. internal acaustic meatus
31
Q

What does the foramen magnum of the posterior cranial fossa transmit?

A
  1. Medulla and meninges
  2. Vertebral arteries
  3. Spinal roots of CN XI
  4. Dural veins
  5. Anterior and posterior spinal arteries
32
Q

What does the jugular foramen of the posterior cranial fossa transmit?

A
  1. CNs IX (glossopharyngeal), X (vagus), and XI (accessory)
  2. Superior bulb of internal jugular vein,
  3. Inferior petrous and sigmoid sinuses
  4. Meningeal branches of pharyngeal and occipital arteries.
33
Q

What does the hypoglossal canal of the posterior cranial fossa transmit?

A

hypoglossal nerve (CNXII)

34
Q

What does the internal acaustic meatus of the posterior cranial fossa transmit?

A

facial, and vestibulocochlear nerves (CNXII)

35
Q

Describe the walls of the cranial cavity?

A
  • Vary in thickness in different regions
  • Thinner in females than men
  • Thinner in children than elderly
  • Bones contains internal and external tables of compact bone
    > Tables separated by diploe
36
Q

Diploe of the walls of the cranial cavity contains?

A
  1. Red bone marrow
  2. Canals containing diploic veins
37
Q

Describe the clinical correlations of the clivus?

A

formed from sphenoid and occipital bones
- the spheno occipital synchodrosis can be seen in children and young adults (not a fracture)
- accounts for majority of skull base growth
- normal fate signals in adult (late teens) in MRI

38
Q

Describe the consequence of posterior cranial fossa fractures?

A

Blood may reappear from under muscles near the mastoid process days afterwards

Head and Neck Anatomy (37 decks)

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