Boney Skull Flashcards
1
Q
What are the immobile joints that unite the bones of the skull called?
A
Sutures
The connective tissue between the bones is called a sutural ligament.
2
Q
What is the exception to the rule of immobile joints in the skull?
A
The mandible
The mandible is united to the skull by the mobile temporomandibular joint.
3
Q
How can the bones of the skull be divided?
A
Into those of the cranium and those of the face
The skull consists of bones that form the cranium and the facial structure.
4
Q
What is the upper part of the cranium called?
A
The vault
The vault forms the dome-like structure of the cranium.
5
Q
What is the lower part of the cranium referred to as?
A
The base of the skull
It provides support to the brain and connects to the vertebral column.
6
Q
What are the two types of bone layers that make up the skull bones?
Which is thinner/more brittle?
A
External and internal tables of compact bone
Internal table = more brittle
These layers are separated by a layer of spongy bone called the diploe.
7
Q
What covers the outer and inner surfaces of the skull bones?
A
Periosteum
The outer layer is called the pericranium and the inner layer is referred to as the endocranium.
8
Q
Fill in the blank: The layer of spongy bone between the external and internal tables of the skull is called the _______.
A
diploe
9
Q
Name the bones of the cranium. Which are paired?
A
- frontal bone
- temporal bones (paired)
- parietal bones (paired)
- sphenoid bone
- occipital bone
- ethmoid bone
10
Q
Name the facial bones. Which are paired and which are single?
A
- zygomatic bones (paired)
- maxillae (paired)
- nasal bones (paired)
- lacrimal bones (paired)
- vomer (single)
- palatine bones (paired)
- inferior conchae (paired)
- mandible (single)
11
Q
Use paper and pen to label :p
A
1) parietal bone
2) mandible
3) mental foramen
4) frontal bone
5) nasal bone
6) optic canal
7) sphenoid bone
8) temporal bone
9) zygomatic bone
10) vomer
11) maxilla
12) incisor
13)
12
Q
What does the frontal bone form in the skull?
A
The upper margins of the orbits
+ anterior part of side of skull. Articulates with parietal bones at coronal suture.
This structure is important for the protection of the eyes and support of facial features.
13
Q
What are the superciliary arches?
A
Prominent ridges on either side of the frontal bone
These arches are often associated with eyebrow positioning.
14
Q
What is the supraorbital notch?
A
An opening in the frontal bone
It can also be referred to as a foramen, allowing nerves and blood vessels to pass through.
15
Q
With which bones does the frontal bone articulate medially?
A
- Frontal processes of the maxillae
- Nasal bones
These articulations are crucial for facial structure and stability.
16
Q
What bone does the frontal bone articulate with laterally?
A
Zygomatic bone
This articulation contributes to the structure of the cheek and the lateral aspect of the orbit.
17
Q
What structures bound the orbital margins?
A
- Frontal bone superiorly
- Zygomatic bone laterally
- Maxilla inferiorly
- Processes of the maxilla and frontal bone medially
The orbital margins are important for the integrity of the eye socket.
18
Q
What are the hollow spaces within the frontal bone called?
A
Frontal air sinuses
These sinuses are lined with mucous membrane.
19
Q
What bones form the bridge of the nose?
A
Nasal bones
The lower borders of the nasal bones, along with the maxillae, create the anterior nasal aperture.
20
Q
What divides the nasal cavity into two parts?
A
Bony nasal septum
The nasal septum is largely formed by the vomer.
21
Q
Which conchae are separate bones from the ethmoid bone?
A
Inferior conchae
The superior and middle conchae are part of the ethmoid bone.
22
Q
Fill in the blank: The two nasal bones form the _______.
A
bridge of the nose
23
Q
What is largely formed by the vomer?
A
Bony nasal septum
24
Q
What do the two maxillae form?
A
The upper jaw, anterior part of the hard palate, part of the lateral walls of the nasal cavities, and part of the floors of the orbital cavities
25
Name the suture between the maxillae
intermaxillary suture
26
What is the function of the infraorbital foramen?
It perforates the maxilla below the orbit
27
What structure does the alveolar process of the maxilla form?
The alveolar arch, which carries the upper teeth
28
Name the sinuses
Frontal, maxillary, ethmoid, sphenoid
29
What does the zygomatic bone form?
- Prominence of the cheek
- part of the lateral wall
- part of the floor of the orbital cavity
30
What does the zygomatic bone articulate with laterally?
The zygomatic process of the temporal bone to form the zygomatic arch
31
What nerves pass through the foramina of the zygomatic bone?
Zygomaticofacial and zygomaticotemporal nerves
Both = branches of V2
32
What are the main components of the mandible?
A horizontal body and two vertical rami
33
1) incisive foramen
2) palatal process of maxilla
3) maxilla
4) palatal process of palatine bone
5) zygomatic arch/temporal process of zygomatic bone
6) Greater palatine foramen (posterior to this = lesser palatine foramen)
7) medial and lateral pterygoid plates of sphenoid bone
8) zygomatic process of temporal bone
9) foramen ovale
10) mandibular fossa
11) external auditory meatus
12) mastoid process
13) mastoid foramen
14) occipital condyle
15) external occipital crest
16) external occipital protuberance
17) supreme nuchal line
18) superior nuchal line
19) inferior nuchal line
20) parietal bone
21) foramen magnum
22) jugular foramen
23) styloid process of temporal bone
24) carotid canal
25) temporal bone
26) vomer
27) sphenoid bone
28) molars
29) pre-molars
30) canines
31) incisors
34
Where does the mental foramen open?
Onto the anterior surface of the body of the mandible, below the second premolar tooth
35
What does the upper border of the mandible/alveolar part of the mandible carry?
The lower teeth
36
What do the parietal bones form in the cranium?
The sides and roof of the cranium
## Footnote
They articulate with each other at the sagittal suture and with the occipital bone at the lambdoid suture.
37
Which bone completes the skull from the side?
The squamous part of the occipital bone
## Footnote
It also includes parts of the temporal bone and the greater wing of the sphenoid.
38
Where is the pterion located?
What articulates here?
2.5cm behind frontal process of zygomatic bone + 4cm above zygomatic arch
Frontal, parietal, temporal and sphenoid bones articulate here
## Footnote
It articulates with the greater wing of the sphenoid and is clinically important due to its proximity to the anterior division of the middle meningeal artery and vein.
39
What is the significance of the pterion?
Thinnest part of lateral wall of skull, overlies the anterior division of the middle meningeal artery and vein
40
What lies below the temporal lines?
The temporal fossa
## Footnote
The lower limit of the temporal fossa is the infratemporal crest of the greater wing of the sphenoid.
41
What is found below the infratemporal crest?
The infratemporal fossa
## Footnote
It is located on the greater wing of the sphenoid.
42
What is the pterygomaxillary fissure?
A vertical fissure within the infratemporal fossa
## Footnote
It lies between the pterygoid process of the sphenoid bone and the back of the maxilla.
43
Where does the inferior orbital fissure lead?
Forward into the orbit
## Footnote
It is located between the greater wing of the sphenoid bone and the maxilla.
44
What is the pterygopalatine fossa?
How does it communicate with
a) infra temporal fossa
b) nasal cavity
c) skull
d) orbit
A small space behind and below the orbital cavity
a) pterygomaxillary fissure
b) sphenopalatine foramen
c) foramen rotundum
e) inferior orbital fissure
## Footnote
It communicates with the infratemporal fossa, nasal cavity, skull, and orbit.
45
What do the posterior parts of the parietal bones articulate with?
The squamous part of the occipital bone
## Footnote
They meet at the lambdoid suture.
46
What is the external occipital protuberance?
A roughened elevation on the occipital bone
## Footnote
It gives attachment to muscles and the ligamentum nuchae.
47
What extends laterally from the external occipital protuberance?
The superior nuchal lines
## Footnote
They extend toward the temporal bone.
48
What is a midline metopic suture?
A failure of the two halves of the frontal bone to fuse
## Footnote
This condition is occasionally observed.
49
What forms the anterior part of the inferior view of the skull when the mandible is discarded?
The hard palate
## Footnote
The hard palate is formed by the palatal processes of the maxillae and the horizontal plates of the palatine bones.
50
What structures are found in the midline anteriorly of the hard palate?
The incisive fossa and foramen
## Footnote
These structures are located in the midline anteriorly of the hard palate.
51
What are the names of the foramina located posterolaterally to the hard palate?
The greater and lesser palatine foramina
## Footnote
These foramina are important for the passage of nerves and blood vessels.
52
What separates the choanae from each other?
The posterior margin of the vomer
## Footnote
The choanae are the posterior nasal apertures.
53
What bone structure is found at the end of the the medial pterygoid plates of the sphenoid bone?
What is at its superior end
The pterygoid hamulus
- superior end has a widening called scaphoid fossa
54
What foramina pierce the greater wing of the sphenoid?
Foramen ovale and foramen spinosum
## Footnote
These foramina allow the passage of important nerves and vessels.
55
What structure can be identified above the medial border of the scaphoid fossa?
The pterygoid canal
## Footnote
connects middle cranial fossa to pterygopalatine fossa
56
What separates the mandibular fossa from the tympanic plate posteriorly?
What exits here?
The squamotympanic fissure
## Footnote
This fissure allows the chorda tympani to exit from the tympanic cavity.
57
What forms the upper articular surfaces for the temporomandibular joint?
The mandibular fossa and the articular tubercle
## Footnote
These structures are part of the temporal bone.
58
Which bones form the foramen lacerum? (be specific)
medial end of petrous part of temporal bone
basilar part of occipital bone
greater wing of sphenoid
59
What is the function of the foramen lacerum during life?
It is closed with fibrous tissue
## Footnote
Only a few very small vessels pass through it from the cavity of the skull to the exterior.
60
What shape does the tympanic plate of the temporal bone have on section?
C-shaped
## Footnote
It forms part of the external auditory meatus.
61
What forms the jugular foramen?
A deep notch in the petrous part of the temporal bone and a shallower notch on the occipital bone
## Footnote
This foramen is important for the passage of cranial nerves and veins.
62
What articulates with the superior aspect of the lateral mass of the atlas?
The occipital condyles
## Footnote
These condyles are critical for the articulation between the skull and the vertebral column.
63
What is contained within the hypoglossal canal?
The hypoglossal nerve
## Footnote
This canal is located superior to the summit of the occipital condyle.
64
What does the cranial cavity contain?
The brain and its surrounding meninges, portions of the cranial nerves, arteries, veins, and venous sinuses
## Footnote
The cranial cavity is essential for protecting and housing the brain.
65
What are the main sutures found on the internal surface of the vault of the skull?
Coronal, sagittal, and lambdoid sutures.
66
Where does the superior sagittal sinus lodge?
In the shallow sagittal groove along the midline.
67
What are granular pits?
Small pits that lodge the lateral lacunae and arachnoid granulations.
68
What is the base of the skull divided into?
Three cranial fossae: anterior, middle, and posterior.
69
What does the anterior cranial fossa lodge?
The frontal lobes of the cerebral hemispheres.
70
What are the anterior and posterior boundaries of the anterior cranial fossa ?
The inner surface of the frontal bone.
The sharp lesser wing of sphenoid
71
What does the medial end of the lesser wing of the sphenoid form?
The anterior clinoid process.
72
What is the function of the anterior clinoid process?
It provides attachment to the tentorium cerebelli.
73
What forms the floor of the anterior cranial fossa?
The ridged orbital plates of the frontal bone laterally and the cribriform plate of the ethmoid medially.
74
What is the crista galli?
A sharp upward projection of the ethmoid bone in the midline for the attachment of the falx cerebri.
75
What is located alongside the crista galli in the cribriform plate?
A narrow slit for the passage of the anterior ethmoidal nerve.
76
What do the small perforations in the cribriform plate allow?
The passage of olfactory nerves.
77
Fill in the blank: The upper surface of the cribriform plate supports the _______.
olfactory bulbs.
78
What does the middle cranial fossa consist of?
A small median part and expanded lateral parts
## Footnote
The median part is formed by the body of the sphenoid, while the lateral parts lodge the temporal lobes of the cerebral hemispheres.
79
What structures bound the middle cranial fossa anteriorly and posteriorly?
Anteriorly by the lesser wings of the sphenoid; posteriorly by the superior borders of the petrous parts of the temporal bones
## Footnote
Laterally, it is bounded by the squamous parts of the temporal bones, the greater wings of the sphenoid, and the parietal bones.
80
What forms the floor of each lateral part of the middle cranial fossa?
What forms the walls?
Greater wing of the sphenoid and the squamous and petrous parts of the temporal bone
Walls = squamous part of temporal bones, greater wing of sphenoid, parietal bones
81
What does the optic canal transmit?
The optic nerve and the ophthalmic artery
## Footnote
The ophthalmic artery is a branch of the internal carotid artery.
82
What forms the superior orbital fissure? What does it transmit?
Slitlike opening between greater and lesser wings of sphenoid
Transmits:
- lacrimal nerve
- frontal nerve
- trochlear nerve
- oculomotor nerve
- nasociliary nerve
- abducent nerve
- the superior ophthalmic vein
## Footnote
83
Where is the sphenoparietal venous sinus located?
Medially along the posterior border of the lesser wing of the sphenoid
## Footnote
It drains into the cavernous sinus.
84
What nerve does the foramen rotundum transmit?
The maxillary nerve
## Footnote
It transmits the nerve from the trigeminal ganglion to the pterygopalatine fossa.
situated behind medial end of superior orbital fissure, perforates greater wing of sphenoid
85
What is the location of the foramen ovale in relation to the foramen rotundum?
Posterolateral to the foramen rotundum
86
What does the foramen ovale transmit?
- large sensory root AND small motor root of the mandibular nerve
- lesser petrosal nerve
## Footnote
87
Where is the foramen spinosum located?
What does the foramen spinosum transmit?
posteriolateral to the foramen oval, perforates greater wing of sphenoid
The middle meningeal artery from inferotemporal fossa to cranial cavity
## Footnote
It runs from the infratemporal fossa into the cranial cavity.
88
Describe the course of the middle meningeal artery
- passes from inferatemporal fossa --> cranial cavity via foramen spinosum
- runs forwards and laterally in groove in on upper surface of the squamous part of the temporal bone and greater wing of sphenoid
- divides into anterior and posterior branches:
- anterior branch passes forwards and up to the anterior inferior angle of the parietal bone
- bone is deeply grooved by the artery which then runs backwards and upwards on parietal bone (this is where tends to be damaged at pterion)
- posterior branch passes backward and upward across squamous part of temporal bone to reach parietal bone
89
What is the function of the middle meningeal artery?
Supplies the dura mater and bones of the skull
## Footnote
It divides into anterior and posterior branches after entering the cranial cavity.
90
Where is the foramen lacerum located?
Between the apex of the petrous part of the temporal bone and the sphenoid bone
91
What enters the foramen lacerum through the carotid canal?
The internal carotid artery
92
What happens to the internal carotid artery after entering the foramen lacerum?
It turns upward to reach the side of the body of the sphenoid bone. Then turns forward in cavernous sinus to reach region of anterior clinoid process
Then turns vertically upwards(medial to anterior crinoid process) and emerges from cavernous sinus
93
True or False: The carotid canal opens into the foramen rotundum.
False
## Footnote
The carotid canal opens into the side of the foramen lacerum.
94
What is located lateral to the foramen lacerum on the apex of the petrous part of the temporal bone?
An impression for the trigeminal ganglion
95
Which two nerves travel in the grooves along the petrous bone?
- Greater petrosal nerve in larger, medial groove (branch of facial nerve)
- lesser petrosal nerve in smaller, lateral groove (branch of tympanic plexus)
96
Where in relation to the trigeminal ganglion does the greater petrosal nerve enter the foramen lacerum? What does it join here?
Enters deep to trigeminal ganglion and joins the deep petrosal nerve (sympathetic fibres from around internal carotid arteries) to form nerve of pterygoid canal
97
What type of fibers does the deep petrosal nerve contain?
Sympathetic fibers
98
Where does the lesser petrosal nerve pass forward to from its groove in the petrous part of the temporal bone?
Foramen ovale
99
The abducent nerve leaves the posterior cranial fossa and enters which sinus?
Cavernous sinus
100
What is the arcuate eminence formed by?
Underlying superior semicircular canal
(seen on anterior surface of petrous bone)
101
What is the tegmen tympani?
A thin plate of bone (forward extension of petrous part of temporal bone that adjoins squamous part of bone) that forms the roof of the mastoid antrum, tympanic cavity, and auditory tube
102
What is the significance of the tegmen tympani?
It is the only major barrier separating infection in the tympanic cavity from the temporal lobe of the cerebral hemisphere
103
What forms the median part of the middle cranial fossa?
Body of the sphenoid bone
104
What is located in front of the sulcus chiasmatis?
Optic chiasma
105
What lies posterior to the sulcus chiasmatis?
Tuberculum sellae
106
What is the deep depression that lodges the hypophysis cerebri?
Sella turcica
107
What bounds the sella turcica posteriorly?
Dorsum sellae
108
What are the two tubercles on the superior angles of the dorsum sellae called?
Posterior clinoid processes
109
What does the cavernous sinus relate to?
Side of the body of the sphenoid
110
Which cranial nerves are carried in the lateral wall of the cavernous sinus?
Third and fourth cranial nerves + V2 and V3
111
Which structures pass through the cavernous sinus?
internal carotid artery and CN VI
112
What structures are lodged in the posterior cranial fossa?
Cerebellum, pons, and medulla oblongata
## Footnote
These are parts of the hindbrain.
113
What are the anterior and posterior boundaries of the posterior cranial fossa?
Anterior: superior border of the petrous part of the temporal bone
Posterior: squamous part of the occipital bone
114
What forms the floor of the posterior cranial fossa?
Basilar, condylar, and squamous parts of the occipital bone and mastoid part of the temporal bone
115
What is the roof of the posterior cranial fossa formed by?
Tentorium cerebelli
116
What does the foramen magnum transmit?
1) Medulla oblongata
2) surrounding meninges
3) ascending spinal parts of the accessory nerves
4) two vertebral arteries
117
The tentorium cerebelli separates which two structures?
Cerebellum and occipital lobes of the cerebral hemispheres
118
True or False: The posterior cranial fossa is shallow and contains the cerebellum.
False - deep and contains cerebellum, pons, medulla
119
What canal transmits the hypoglossal nerve?
The hypoglossal canal
## Footnote
The hypoglossal canal is located above the anterolateral boundary of the foramen magnum.
120
Where is the jugular foramen located?
Between the lower border of the petrous part of the temporal bone and the condylar part of the occipital bone
## Footnote
The jugular foramen transmits several important structures.
121
Which structures are transmitted by the jugular foramen from front to back?
* The inferior petrosal sinus
* The ninth cranial nerve
* The tenth cranial nerve
* The eleventh cranial nerve
* The large sigmoid sinus
## Footnote
These structures are critical for various functions including venous drainage and nerve signaling.
122
Describe the course of the inferior petrosal sinus
Descends in the groove on the lower border of the petrous part of the temporal bone to reach the jugular foramen. Becomes internal jugular vein as it passes through the jugular foramen.
## Footnote
It is part of the venous drainage system of the brain.
123
What nerve is transmitted by the internal acoustic meatus?
The vestibulocochlear nerve + motor and sensory roots of facial nerve
## Footnote
pierces posterior surface of petrous part of temporal bone
124
What does the internal occipital crest attach to?
The small falx cerebelli over the occipital sinus
## Footnote
The internal occipital crest runs upward from the foramen magnum.
125
What is located on each side of the internal occipital protuberance?
A wide groove for the transverse sinus
## Footnote
This groove connects to the posterior inferior angle of the parietal bone.
126
What does the transverse sinus become after passing onto the mastoid part of the temporal bone?
The sigmoid sinus
## Footnote
The sigmoid sinus is a crucial part of the venous drainage system.
127
Where does the superior petrosal sinus drain?
Into the sigmoid sinus
## Footnote
It runs backward along the upper border of the petrous bone.
128
True or False: The sigmoid sinus lies directly anterior to the mastoid antrum as it descends to the jugular foramen.
False
## Footnote
The sigmoid sinus lies directly posterior to the mastoid antrum.
129
What are the three membranes that surround the brain and spinal cord?
Dura mater, arachnoid mater, pia mater
130
What are the two layers of the dura mater?
Endosteal layer, meningeal layer
131
What is the function of the endosteal layer of the dura mater?
Covers the inner surface of the skull bones
132
Does the endosteal layer of the dura mater extend through the foramen magnum?
No
133
What does the meningeal layer of the dura mater cover?
The brain
134
What does the meningeal layer of the dura mater provide for cranial nerves?
Tubular sheaths
135
What do the septa sent inward by the meningeal layer do?
Divide the cranial cavity into freely communicating spaces
136
What is the function of the falx cerebri?
Lies in the midline between the two cerebral hemispheres
137
Where is the falx cerebri attached at its narrow end?
Internal frontal crest and crista galli
138
What runs along the upper fixed margin of the falx cerebri?
Superior sagittal sinus
139
What is the shape of the tentorium cerebelli?
Crescent-shaped
140
What does the tentorium cerebelli cover?
Upper surface of the cerebellum
141
What is the gap in the tentorium cerebelli called?
Tentorial notch
142
What cranial nerves pass forward at the point where the fixed and free borders of the tentorium cerebelli cross?
Third and fourth cranial nerves
143
1) parietal bone
2) squamous part of temporal bone
3) lambdoid suture
4) occiput
5) external auditory meatus in tympanic plate
6) mastoid process of temporal bone
7) mandible (ramus vs angle)
8) mental foramen
9) body of mandible (note part by teeth = alveolar part)
10) coronal suture
11) frontal bone
12) Greater wing of sphenoid
13) ethmoid bone
14) nasal bone
15) lacrimal bone
16) zygomatic bone
17) maxilla
18) zygomatic arch (union of temporal process of zygomatic bone + zygomatic process temporal bone at zygomaticotemporal suture)
144
What are fractures of the skull more common in?
Adults
## Footnote
Fractures of the skull are very common in adults, but much less so in young children.
145
How do the bones of the infant skull compare to those of an adult skull?
More resilient and separated by fibrous sutural ligaments
## Footnote
Infant skull bones are more resilient than adult skull bones.
146
What happens to the sutural ligaments during middle age?
They begin to ossify
147
What type of fracture occurs in the adult skull when subjected to a severe localized blow?
Local indentation with splintering of the bone
148
What is the analogy used to describe the adult skull?
Eggshell
149
What type of fractures result from blows to the vault of the skull?
Linear fractures that radiate out
150
What analogy is used to describe the young child's skull?
Table-tennis ball
151
What type of fracture is referred to as a 'pond' fracture?
Circumscribed lesion from a localized blow in children
152
What may be damaged in fractures of the anterior cranial fossa?
Cribriform plate of the ethmoid bone
153
What are the symptoms of a fracture involving the cribriform plate?
Epistaxis and cerebrospinal rhinorrhea
154
What results from fractures involving the orbital plate of the frontal bone?
Hemorrhage beneath the conjunctiva and into the orbital cavity
155
What is a common consequence of fractures of the middle cranial fossa?
Leakage of cerebrospinal fluid and blood from the external auditory meatus
156
Which cranial nerves may be involved in fractures of the middle cranial fossa?
Seventh and eighth cranial nerves
157
What can occur if the lateral wall of the cavernous sinus is torn?
Damage to the third, fourth, and sixth cranial nerves
158
What may happen to blood and cerebrospinal fluid in the event of a fracture?
Leak into the sphenoidal air sinuses and then into the nose
159
What can fractures of the posterior cranial fossa cause?
Blood to escape into the nape of the neck
160
What is a common sign of fractures of the facial bones?
Deformity and ocular displacement
161
What is a common type of fracture in the nasal bones?
Simple fractures
162
What is the common result of fractures of the maxilla?
Malocclusion of the teeth
163
What is often a result of a direct anteroposterior blow to the face?
Fractures of the maxilla
164
How may the zygoma or zygomatic arch be fractured?
By a blow to the side of the face
165
What may be associated with zygomatic arch fractures?
Multiple other fractures of the face
166
What shape does the mandible have?
Horseshoe-shaped
167
What forms a bony ring with the mandible?
Two temporomandibular joints and the base of the skull
168
How does traumatic impact affect the mandible?
It causes a single fracture or multiple fractures, often far removed from the point of impact
169
What results from injuries to the brain upon impact?
Displacement and distortion of the neuronal tissues
170
How can the brain be likened in terms of its positioning?
Like a log soaked with water floating submerged in water
171
What limits the lateral displacement of the brain?
The falx cerebri
172
What anatomical structures restrict displacement of the brain?
* Tentorium cerebelli
* Falx cerebelli
173
What type of blows to the head can lead to severe cerebral damage?
Blows to the front or back of the head
174
What is the neurocranium?
A protective case around the brain
175
What initial structure represents the parts of the skull?
A sheet of condensed mesenchyme
176
What types of transformation can the initial mesenchyme undergo?
* Membrane
* Bone
* Cartilage
177
What is the chondrocranium?
A unified mass of cartilage at the base of the skull by the middle of the third month of prenatal life
178
When does ossification of the chondrocranium begin?
Early in the third month of prenatal life
179
What bones form the membranous neurocranium?
* Frontals
* Parietals
* Squamous portion of the occipital bone
180
What is the significance of bone mobility in the skull at birth?
It allows for the molding of the cranium during childbirth
181
Fill in the blank: Most of the bones of the skull are ossified by the time of ______.
Birth
182
What are the right and left halves of the mandible united by at birth?
Fibrous tissue
183
At what age do the two halves of the mandible fuse at the symphysis menti?
By the end of the first year
184
What shape is the angle of the mandible at birth?
Obtuse
185
What anatomical feature lies at a superior level to the head of the mandible at birth?
Coronoid process
186
What causes the angle of the mandible to assume its adult shape?
Eruption of the permanent teeth
187
What happens to the size of the mandible in old age?
It is reduced when a person loses teeth
188
What changes occur to the ramus of the mandible as the alveolar part of the bone becomes smaller in old age?
The ramus becomes oblique in position
189
What is cranioschisis?
Anomaly where the vault of the skull is open
190
Cranioschisis is usually associated with which condition?
Anencephaly
191
What is ocular hypertelorism characterized by?
Widely separated eyes
192
What causes ocular hypertelorism?
Overgrowth of the lesser wing of the sphenoid
193
What does craniosynostosis mean?
Premature fusion of some of the cranial sutures
194
What happens if the sagittal suture is involved in craniosynostosis?
The skull becomes elongated in anteroposterior diameter
195
What shape does the skull take if the coronal suture fuses early?
Turret-shaped
196
What may craniosynostosis lead to due to increased cerebrospinal fluid pressure?
Mental retardation
197
What surgical procedure may be required in craniosynostosis?
Craniectomy
198
What is plagiocephaly?
Asymmetric head shape caused by irregular fusion of cranial bones
199
What may cause plagiocephaly?
Excessive pressure on one part of the developing skull in utero
200
True or False: Plagiocephaly is caused by the molding that occurs during labor.
False
201
What is the developmental outcome for a child with plagiocephaly?
Develops perfectly normally
