Skull and Meninges Flashcards
1
Q
In the cranium which bones are paired? (2)
A
Temporal Parietal
2
Q
In the cranium which bones are NOT paired? (4)
A
Frontal Occipital Ethmoid Sphenoid
3
Q
In the face which bones are paired? (6)
A
Maxillary Zygomatic Lacrimal Nasal Inferior nasal concha Palatine
4
Q
In the face which bones are NOT paired? (2)
A
Mandible Vomer
5
Q
What are the ossicles of the ear? (3)
A
Malleus Incus Stapes
6
Q
What are the bones of the skull? (4)
A
Cranium Face Ossicles of Ear Hyoid
7
Q
What variations in the skull do infant skulls show?
A
The frontal bone in two halves separated by the metopic (interfrontal) suture. This suture is usually replaced with bone by 6-8 years but in minority of individuals may persist into adult life
8
Q
What is a suture comprised of?
A
Fibrous connective tissue.
9
Q
What are sutures replaced with in adult life? What is an example?
A
Bone. The lambdoid suture is obliterated in most individuals in the range 21-42 years.
10
Q
What is the main part of the bone referred to as?
A
Body
11
Q
What are processes/plates/spines? What purpose do they serve? Provide an example for each.
A
Bony extensions from the body. 1. For articulations with other cranial bones 2. For attachments of muscles or ligaments Temporal process of zygomatic bone which articulates with the zygomatic process of the temporal bone. Medial and lateral pterygoid plates - for attachment of muscles of pharynx, mastication, soft palate
12
Q
What is an eminence? What is an example?
A
A bony bump of elevation overlying some deep structure. Arcuate eminence in the middle cranial fossa over inner ear (within bone)
13
Q
What are impressions?
A
Grooves on the surface of bone indicating the presence of some overlying soft tissue structure.
14
Q
When do soft tissue structures usually form? What is an example?
A
Before bone is laid down. Grooves for middle meningeal artery and its branches inside squamous part of temporal bone.
15
Q
What is the function of openings/foramina/fossae/canals?
A
To allow cranial nerves and veins to leave the skull and arteries to enter the skull. They connect the inside of the skull with the outside.
16
Q
Nerves and blood vessels develop first and the bone forms later around them. True or False?
A
True.
17
Q
What do large foramina provide access for? What is an example?
A
Major structures. Internal carotid, facial nerve
18
Q
What do small openings and canals allow the transmission of in the skull? What is an example?
A
Small branches of cranial nerves. For example, the chorda tympani - nerve involved in taste
19
Q
What are small openings for small vessels called? Why are they important? What is an example?
A
Emissary foramina. These can be clinically significant. For example, the communication between the pterygoid venous plexus on the outside of the skull and the cavernous sinus on the inside of the skull.
20
Q
Particular foramina can vary in number or can be absent. True or False?
A
True.
21
Q
What is the meatus? What are 2 examples?
A
Relatively large tube-like passage way. External acoustic meatus. Groove for cartilaginous part of auditory tube.
22
Q
The external acoustic meatus is posterior to the mastoid process. True or false.
A
False, it is anterior. The external acoustic meatus leads from the external surface of the head to the eardrum (tympanic membrane).
23
Q
What doe the superior and inferior temporal lines cross?
A
Parietal and temporal bones.
24
Q
What attaches to the superior and inferior temporal lines?
A
Temporalis and its overlying fascia.
25
What does the zygomatic bone form?
The prominence of the cheek and part of the side wall of the orbit.
26
What does the frontal process of the zygomer articulate with?
Frontal bone in the lateral orbital margin.
27
Where is the zygomaticofacial foramen usually present?
The lateral side of the base of the frontal process of the zygomer.
28
Where is the zygomaticotemporal foramen?
Medial side of base of frontal process of zygomer.
29
What does the temporal process of the zygomer articulate with? What does it form?
Zygomatic process of the temporal bone to form the zygomatic arch.
30
What does the temporal bone consist of?
1. Temporal fossa
2. Infratemporal fossa
31
What is the temporal fossa?
Indentation inferior to the temporal lines.
32
The infratemporal fossa is inferior to the temporal fossa and medial to the zygomatic arch. True or false?
True.
33
What does the infratemporal fossa open medially into?
Pterygopalatine fossa beneath the orbit.
34
What are the two parietal bones separated by?
Saggital suture.
35
At the posterior end of the parietal bones what strucutre is found? What does it separate?
Lambdoid suture. It separates the parietal bones from the occipital bone.
36
What is the floor in the anterior cranial fossa?
Orbital plate of the frontal bone (roof of the orbit) and lesser wing of the sphenoid.
37
What do the two orbital plates of the frontal bone articulate with medially? What does this structure transmit? Where does it transmit it to?
Cribriform plate of the ethmoid. Olfactory nerve filaments from the nose to the cranial cavity.
38
What does the cribriform plate form?
Part of the roof of the two nasal cavities.
39
What is the crista galli (ethmoid bone)? What attaches there?
Median bony crest that projects superiorly from the cribriform plate. Falx cerebri
40
What is the floor of the middle cranial fossa?
Body of sphenoid medially and greater wings of sphenoid laterally.
41
What is posterolateral in the middle cranial fossa?
Petrous and squamous temproal bones.
42
What impressions may be recognisable on the medial part of the petrous temporal bone?
Trigeminal
43
What crosses the thin squamous temporal bone.
Grooves for branches of the middle meningeal artery.
44
What does the hypophyseal fossa (sella turcica) contain?
Pituitary gland (hypophysis cerebri)
45
What are the bony projections overhanging the fossa?
Anteior and posteiror clinoid process.
46
What is the dorsum sellae?
Bony ridge between posterior clinoid processes.
47
What does the petrous temporal bone at the posterior end of the middle cranial fossa encase?
The organs of hearing and balance.
48
What is the arcuate eminence?
A bony bump of petrous temporal bone which overlies the superior/anterior semicircular canal of the inner ear.
49
What is the trigeminal impression?
An indentation on posteromedial part of petrous tempral marking the position of the trigeminal ganglion.
50
What is the tegmum tympani?
Indented region of bone anterolateral to the arcuate eminence (overlies the middle ear)
51
What are the openings in the middle cranial fossa and what do they transmit respectively?
1. Optic canal (transmits optic nerve CNII) 2. Superior orbital fissure (transmits CNs III, IV, brahnces of CN V/1, VI) 3. Foramina rotundum (maxillary nerve CN V/2) 4. Foramen ovale (mandibular nerve CN V/3) 5. Foramen spinosum (middle meningeal artery) 6. Foramen lacerum (internal carotid enters skull via carotid canal, traverses posterior wall of foramen lacerum to enter middle cranial fossa; also transmits greater petrosal nerve - branch of facial nerve)
52
What is the floor of the posterior cranial fossa?
Occipital bone which surrounds the foramen magnum.
53
Where is the clivus located?
Between the hypophyseal fossa and foramen magnum.
54
What are the openings of the posterior cranial fossa? What does it transmit?
1. Internal acoustic meatus (temporal) - transmits facial (CN VII) and vestibulocochlear nerve (CN VIII) 2. Jugular foramen (lateral to foramen magnum) - transmits CN IX (glossopharyngeal), CN X (vagus), CN XI (accessory) and internal jugular 3. Foramen magnum 4. Hypoglossal canal (wall of foramen magnum) - transmits hypoglossal nerve (CN XII)
55
What does the hard palate consist of?
Palatine process of maxillae (anterior) and horizontal plate of palatine bone (posteromedial)
56
The pyramidal process of the palatine bone is posterior to the maxillary tuberosity. True or false.
True.
57
Where does the pyramidal process of the palatine bone extend?
Into the pterygoid fossa between the two pterygoid plates.
58
What are the sutures of the hard palate?
Intermaxillary, interpalatine and palatomaxillary
59
What are the openings of the hard palate? Where are they located?
1. Incisive fossa/canal is just behind the incisors 2. Greater and lesser palatine foramina are at the posterolateral end of the palatine bone.
60
What bone is the articular fossa a part of? What is its function?
Temporal bone. Condyle of the mandible.
61
What is the pterygoid plate comprised of?
Medial and lateral pterygoid plates with pterygoid fossa between them.
62
What is the hamulus?
Bony hook on the anteroinferior medial plate.
63
Where is the scaphoid fossa located?
At the posterior end of the medial pterygoid plate.
64
Where are the choanae? What is it separated by?
Posterior nasal openings separated by bony nasal septum.
65
What is the bony nasal septum posterioinferiorly and anterosuperiorly?
Vomer and perpendicular plate of ethmoid.
66
Which conchae are part of the ethmoid bone?
Superior and middle. The inferior concha is a separate bone.
67
What are the features of the occipital bone?
Nuchal lines Foramen magnum
68
What attaches to the nuchal lines?
Attachment of neck muscles
69
Where are the occipital condyles in relation to the foramen magnum?
Lateral
70
What do the occipital condyles articulate with?
Atlas
71
What attaches to the pharyngeal tubercle? Where?
Pharyngeal constrictor muscles on basilar occiput.
72
What is the part of the occipital bone anterior to the foramen magnum? What does it include?
Basilar part. Pharyngeal tubercle.
73
What is the function of the articular fossa?
For articulation with mandible
74
What does the condylar canal transmit?
Emissary vein
75
What are the openings on the inferior aspect? Where are they located?
1. Petrotympanic fissure. Posterior to articular fossa (exit of chorda tympani - branch of facial nerve - taste) 2. Stylomastoid foramen. Between mastoid and styloid processes. (Exit of facial nerve) 3. Palatopharyngeal (palatovaginal) canal. Posterolateral to nasal septum. 4. Pterygoid canal. Posterior to medial pterygoid plate - between scaphoid fossa and foramen lacerum. 5. Carotid canal - entry of internal carotid 6. Opening of bony auditory tube. Medial to spine of sphenoid. 7. Foramina ovale, spinosum, lacerum, jugular foramen.
76
What does a groove running into the opening of the bony auditory tube indicate?
Position of cartilaginous part of auditory tube.
77
The foramen rotundum opens into the articular fossa. True or false?
False. It opens into the pterygopalatine fossa.
78
What are the processes and notches on the inferior aspect? Where are they located?
1. Mastoid (temporal bone) 2. Mastoid notch/digastric notch/digastric groove 3. Styloid process (temporal bone - often damaged) anteromedial to mastoid 4. Spine of sphenoid (Irregular bony bump between foramen spinosum and carotid canal - sphenomandibular ligament - part of stabilising structures of TMJ attaches here)
79
What are the openings of the orbit on the posterior wall? What do they transmit?
1. Optical canal (for optic nerve CNII) 2. Superior orbital fissure (transmits cranial nerves to orbit plus opthalmic nerve - division of trigeminal nerve) 3. Inferior orbital fissure (transmits maxillary nerve - division of trigeminal - from pterygoid fossa
80
What are the openings of the orbit on the floor? What do they transmit?
1. Infraorbital canal and foramen - transmits infraorbital nerve (terminal branch of maxillary nerve)
81
What are the openings of the orbit on the medial wall? What do they transmit?
1. Anterior and posterior ethmoid canals (for branches of opthalmic division of trigeminal) 2. Lacrimal canal (drainage of tears)
82
What are the openings of the orbit on the lateral wall? What do they transmit?
1. Zygomatic-orbital foramen (for zygomatico-orbital branch of maxillary nerve)
83
What are the emissary foramina?
Openings in the bone of the skull which transmit veins connecting dural venous sinuses with venous structures outside the skull.
84
In which direction is blood in emissary veins usually directed?
They can flow in either direction but is usually towards the outside of the skull
85
Why are emissary veins clinically important?
They provide a possible route of infection from the outside of the skull to the brain.
86
Where is the sphenoid emissary foramen located?
Anteromedial to the foramen ovale.
87
Divisions of the paranasal sinuses are paired. True or false.
True. However, the divisions may be incomplete
88
Why are mastoid air cells not paranasal sinuses?
Because they do not open into the nasal cavities.
89
What is the mylohyoid nerve a branch of?
Inferior alveolar nerve
90
How are paranasal sinuses named?
According to the bone in which they are located.
91
Paranasal sinuses are all similar in size and pattern. True or false.
False
92
What are the four paranasal sinuses and what are they bound by?
1. Maxillary (bounded by lateral walls of nose, floor of orbit and alveolar arch of maxilla) 2. Frontal (posterosuperior to superciliary arches - brow ridges) 3. Sphenoid (between upper nasophayrnx and hypophyseal fossa) 4. Ethmoid (multiple small cavities - air cells - between upper nasal cavity and orbit)
93
What does the body of the mandible contain?
1. Alveolar arch/process
94
What does the ramus contain? What is it separated from and by what?
Coronoid process. It is separated from condyle (part of temporomandibular joint) by mandibular notch/incisure
95
What does the medial mandible with mandibular foramen lead into?
Mandibular canal
96
Where does the mylohyoid line run?
Obliquely across body from below the 3rd molar to mental symphysis (attachment of mylohyoid muscle - floor of mouth)
97
Where does the mylohyoid groove run?
Runs anteromedially from mandibular foramen
98
Where are the mental spines located?
Medial and above mylohyoid line.
99
Where is the digastric fossa located?
Near midline on medial surface of mandible
100
Where is the mental foramina located?
On external surface below 2nd premolars
101
What are the features of the dura?
1. External 2. Dense 3. Inelastic
102
What are the two layers of the dura?
Periosteal layer and a meningeal layer
103
What are the characteristics of the periosteal layer?
It is firmly adherent to bone of skull (no epidural space - epidural space is only present in vertebral column)
104
The two layers of the dura are essentially fused? True or False.
True.
105
What are the execeptions for the fusing of the dura?
1. Cavities for vessels (including dural sinuses) or nerves (including the most peripheral part of trigeminal nerve and cavity for the trigeminal ganglion) 2. Where the meningeal layer forms extenstions or folds
106
What are the dural sinuses?
Endothelial lined spaces between the layers of dura.
107
What are the dural sinuses responsible for?
Draining blood from brain and cranial bone
108
Dural sinuses have valves. True or False
False
109
Where do dural sinuses ultimately drain?
Internal jugular
110
What does the falx cerebri separate?
Within the longitudinal fissure between the cerebral hemispheres
111
What does the tentorium cerebelli seaparate?
Between cerebellum and ocipital lobe of cerebral hemispheres
112
What does the falx cerebelli separate? What is it attached to?
Folds into posterior cerebelli notch to partly separate cerebellar hemispheres. It is attacged to the inferior surface of tentorium cerebelli.
113
What does the sella diaphragm seaparate? What does it have an opening to accomodate?
Covers sella trucica and contained pituitary. Infundibulum
114
The sella diaphragm is continuous with dura of the floor of the middle cranial fossa. True or False?
True.
115
What are the features of the arachnoid?
It is thin, covers the brain but does not penetrate sulci except longitudinal fissure
116
What does the arachnoid meninges contain?
Consists of arachnoid and arachnoid trabeculae which cross the subarachnoid space to join pia.
117
What does the subarachnoid space contain?
CSF
118
What are the features of the pia mater?
1. Thin innermost membrane. 2. Closely attached to sruface of brain an folds into sulci.
119
Which openings does CN1 pass through?
Cribriform plate to upper nasal cavities
120
Which openings does CNII pass through?
Optic canal to orbit
121
Which openings does CNIII, IV pass through?
Superior orbital fissure to orbit
122
Which openings does CNV pass through?
1. Opthalmic - superior orbital fissure to orbit. Branches exit orbit via supraorbital foramen or notch and anterior and posterior ethmoid foramina 2. Maxillary - foramen rotundum --\> pytergopalatine fossa --\> inferior orbital fissure --\> orbit. Bracnhes exit orbit via zygomatico-orbital foramen and infraorbital canal 3. Mandibular - foramen ovale
123
Which openings does CNVII pass through?
Internal acoustic meatus to styloatoid foramen.
124
Which openings does CNVIII pass through?
Internal acoustic meatus
125
Which openings does CNIX, X, XIpass through?
Jugular foramen
126
Which openings does CNXII pass through?
Hypoglossal canalo
127
Where openings does CNVI pass through?
Superior orbital fissure
128
What is the petrotympanic fissure for? Is the structure anterior or posterior to the fissure?
Chorda tympani
