Osteology Of Skull Flashcards
What are the parts of the cranium called?
Neurocranium
Viscerocranium
What are sutures?
The fibrous joints between the bones of the cranium
What is the term for depressions?
Fossae
What is the name given to roundish holes?
Narrow slits?
Foramina
Fissures
What is the function of the Neurocranium?
Encases and protects brain
What make up the Neurocranium?
Calvaria/skull cap made of the cranial floor and cranial cavity
How do the vault bones of the Neurocranium form?
Start as membranes then ossify (intrramembranous ossification)
Floor/ base starts as cartilage (Endochondral ossification)
What part of the skull makes up the viscerocranium?
Facial skeleton and jaw
How do the viscerocranium bones form?
Begin as membranes or cartilage and ossify
What is the name of the embryological structure that gives rise to the head and neck?
Pharyngeal arches (1,2)
What are the bones of the Neurocranium that are visible(calvaria/skull)?
Frontal bone
Parietal bones
Temporal bone
Occipital bones
What is the bone that forms the forehead?
Frontal bone
What is it called when the left and right frontal bones dont fuse together at the midline?
Metopic suture
What is the name of the bone that is posterior to the frontal bone?
Parietal bone (left and right parietal bone)
What is the name of the main bone that forms the lateral aspect of the Neurocranium?
Temporal bone
What is the name of the part of the temporal bone that houses the delicate structures of the inner and middle ear?
Petrous part of temporal bone
What is the name of the bone visible on the lateral aspect of the Neurocranium that’s anterior to the temporal bone but posterior to the orbital cavity?
Greater wing of sphenoid bone
What is the main bone forming the posterior aspect of the skull?
Occipital bone
What part of the occipital bone articulates with the C1 vertebra?
Occipital condyles
Look at the end of the lecture and label the bones of the Neurocranium
Blue = frontal bone
Red = parietal bones
Pink = temporal bone
Green = greater wing of sphenoid
Yellow = occipital bone
What is the name of the suture on the top of the skull joining the frontal bone and the parietal bone?
Coronal suture
What is the name of the suture joining the 2 parietal bones?
Sagittal suture
What is the name of the suture joining the occipital bone and the 2 parietal bones?
Lambdoid suture
What is the name of the point where the coronal suture and Sagittal suture meet?
Bregma
What is the name of the point where the Sagittal suture and lambdoid suture meet?
Lambda
What is the name of the large areas of unossified membranous gaps between flat bones of the calvaria which are present in development?
Anterior fontanelle
Posterior fontanelle
Go to slide 10 to look at the sutures and points that the suture meet
What is the importance of the fontanelles in the infant?
Allows for the skull size to increase as the brain size increases
What is the name of the condition where the fontalleles and sutures fuse too early?
Craniosynostosis
How should the anterior fontanelle appear in a healthy baby?
Slightly convex
What is concave and what is convex?
Concave is a U shape (imagine a bombs gone off in the ground)
Convex is a n shape
What does a bulgining anterior fontanelle indicate?
What does a sunken anterior fontanelle indicate?
Bulging = high intercranial pressure
Sunken = dehydrate/low intercranial pressure
How are the bones of the calvaria specially structured to provide strength?
Trilaminar arrangement
Describe the trilaminar arrangement of the bones of the calvaria:
Inner table (compact bone)
Spongy bone (dipole)
Outer table (compact bone)
What is the name of the membrane covering the surfaces of the outer and inner table of the skull bones?
Periosteum
Where are arteries located within the structure of the trilaminar arrangement of the skull bones?
Between the periosteum and the bone (inner table)
What are the 3 types of intracranial haemorrhages that can form as a result of bleeding from the artery between the periosteum and the bone?
Subarachnoid haemorrhage
Subdural haemorrhage
Extramural haemorrhage
What type of intracranial haemorrhage is a lentiform appearance characteristic of? (look at slide 14)
Extradural haemorrhage
What artery is ruptured in an Extradural haemorrhage?
Middle meningeal artery
What creates the lentiform appearance for an Extradural haemorrhage?
The bleeding from the middle meningeal artery strips the periosteals layer from the inner table but it isn’t strong enough to stir the periosteum at the ends
What are the names of the 3 depressions making the cranial floor?
Anterior cranial floor/fossa
Middle cranial floor
Posterior floor
What is the rough shape of the middle cranial fossa?
Butterfly shaped
What are the bones that form the anterior cranial floor?
Frontal bone
Ethmoid bone
Lesser wing of sphenoid
Where is the ethmoid bone located in the anterior cranial floor?
In between the orbital planes which is the parts of the frontal bone overlying the orbits
What cavity does the ethmoid bone form a key part of?
Nasal cavity
What is the name of the part of the ethmoid bone visible when looking at the anterior cranial floor?
What does it attatch to?
Look at slide 18
Crista galli
Dural fold
What is the name of the flat rectangular plate that the crista galli attaches to?
Cribriform plate
What is the name of the long protuberance that separates the nasal cavity into 2 halves?
Perpendicular plate/vomer
What nerve passes through the perforations in the cribriform plate to roof of nasal cavity?
Olfactory nerve
What bone is present in both the anterior and middle cranial floor?
Sphenoid bone
(Lesser wing = anterior floor)
(Greater wings = middle floor)
What is the central bony prominence of the greater wing of sphenoid in the middle cranial floor?
Sella turcica
What is the central depression of the sella turcica called?
Pituitary fossa
What are some key parts of the temporal bone? (slide 20(
Zygomatic process which forms shape of cheek
Mastoid process
Petrous bone
Squamous part
What is important about the Petrous part of the temporal bone?
Its very hard so it can protect the very delicate structures of the inner ear
What is the palpable part of the occipital bone called?
Occipital protuberance
What iis the curved line at the back of the occipital bone called and what attaches here?
Superior nuchal line
Trapezius attaches here
What is the name of the hole which the brainstem continues through becoming the spinal cord?
Foramen magnum
Why is significant traum needed to force a skull fracture?
Trilaminar structure very strong
What is a linear skull fracture?
When the fracture line is fairly straight and theres no bone displacement
What is a comminuted fracture?
Fragments multiple fracture lines which can be depressed or non depressed
Why are comminuted fractures which have depressed dangerous?
Can displace into the brain
What is the Pterion?
Where the 4 bones of the Neurocranium (vault/skull cap) join together on the lateral side
Why are blows to the lateral side of the head (pterion) dangerous?
Pterion is relatively weak
Medial meningeal artery located underneath it which can consequently cause an extra dural intercranial haemorrhage
What is a characteristic feature of an orbital plate fracture of the anterior cranial fossa?
Periorbital ecchymosis (raccoon eyes)
What are the 3 characteristic indications of a fracture to the Petrous bone in the middle cranial floor?
Blood + CSF out of ear (otorrhea)
Battles sign (bruising of mastoid process)
Haemotympanum (blood pooling in middle ear cavity since tympanic membrane is leaking blood)
What is indicative of an anterior cranial floor/fossa fracture involving the ethmoid bone?
Clear fluid (CSF) dripping from nose
What are the bones of the viscerocranium?
Zygomatic (2bones)
Maxilla
Nasal
Lacrimal
Mandible
Look at the last slide
Name the bones
Blue = zygomatic bones
Red = maxilla
Yellow = nasal
Purple = lacrimal
Green = mandible
Why do impacts to the supraorbital ridge usually lead to laceration?
The supraorbital ridge of the frontal bone is very tough
What are the 3 bones commonly fractured in the face?
Nasal bones
Zygomatic bone and arch
Mandible
What type of x-ray is taken if a mandibular fracture is suspected?
OPG xray
What type of joint is the temporomandibular joint (TMJ)?
Synovial hinge-type joint between mandible at condyles and temporal bone
What separates the tempormandibular joint into 2 synovial cavities?
Fibrocartilaginous disc
What is Tempormandibular joint disorder?
Pain around the joint with clicking and locking
What nerve innervates the temporomanidibular joint?
Auriculotemporal nerve which is a branch of the mandibular division of the Trigeminal nerve
What stabilises the TMJ?
Joint capsule
3 extracapsular ligaments
What is the function of the inferior joint capsule of the TMJ?
Rotation
What is the function of the superior joint capsule of the TMJ?
Gliding function
Hoe does the jaw open with reference to the motions due to the superior and inferior joint capsule?
Inferior capsule rotates
Superior joint capsule glides forward (condyle slide onto articular tubule)
What are the 4 muscles of mastication?
What is the innervation?
Temporalis
Masseter
Lateral pterygoids
Medial pterygoids
Mandibular division of the Trigeminal nerve
What muscles elevate the mandible at the TMJ?
Masseter
Temporalis
Medial pterygoids
What muscle depresses the mandible at the TMJ?
Lateral pterygoids
Platysma (against resistance)
What muscles do protraction at the TMJ??
Lateral pterygoids
Medial pterygoids
What leads to a TMJ dislocation?
When the condyle passes in front of the articular tubercle
What leads to the jaw locking once it has anteriorly displaced/dislocated?
Muscles of mastication around joint keep it locked
What leads to the jaw locking once it has anteriorly displaced/dislocated?
Muscles of mastication around joint keep it locked
How is a dislocated TMJ fixed?
Reduced by pushing down on jaw and sliding condyle back in the mandibular fossa
