Prac 2: Anatomy of External Skull Flashcards
Excluding the 32 teeth and 6 auditory ossicles, how many bones are in the skull?
22
What types of joints exist between bones of the skull?
All fibrous (sutures) -> which ossify in adults over a variable amount of time
Aside from auditory ossicles, the only non-fibrous joint is the Temporomandibular Joint (TMJ) = Bilateral synovial hinge
What portion is the neurocranium?
The portion surrounding the brain - more dorsal
What portion is the facial skeleton?
Anterior and lower portions of the skull
List the facial bones. Which ones aren’t paired?
Mandible (unpaired) Vomer (unpaired) Maxilla (2) Zygomatic (2) Lacrimal (2) Nasal (2) Inferior Nasal Concha (2) Palatine (2)
Bones of the neurocranium are?
Frontal, Occipital, Parietal (2), Temporal (2), Sphenoid and Ethmoid
What are the two divisions of the neurocranium?
Calvaria (skull cap)
Cranial Base: Cranial base further divided into Anterior, Middle and Posterior Fossae
Coronal suture - between which bones?
Frontal and Parietal
Lambdoid Suture?
Parietal and Occipital
Sagittal Suture?
Between the 2 parietal bones
Squamosal Suture?
Arches posteriorly from the pterion, from the temporal squama to the lower border of parietal bone
What is the Lambda?
Meeting of the sagittal and lambdoid sutures
thus meeting of the two parietal bones and occipittal bone, posteriorly
What is the Bregma?
Meeting of the Sagittal and Coronal sutures
thus of frontal bone and parietal bones
What is the vertex?
Highest point of the skull
Formed by 4 bones: Frontal, 2 parietals and the occipital
What is the Pterion?
Short suture on the lateral side of the skull where the greater wing of the sphenoid articulates with 3 other bones:
- Temporal (squamous part)
- Frontal
- Parietal
What is the asterion?
At the articulations of the Parietal, Occipital and Temporal Bones - posterolaterally
What is the nasion?
Meeting of the nasal and frontal bones
What is the inion?
The most prominent part of the external occipital protuberance
What are the articulating portions involved in the TMJ?
The head of the condylar proces of mandible
with
Mandibular fossa of temporal bone
By what type of joint are the teeth attached to the mandible and maxilla?
Gomphoses - fibrous peg-in-socket joints
From teeth to the inferior (mandible) and superior (maxilla) alveolar processes
Where is the mandibular foramen located? Where does it lead?
Medial aspect of the ramus of mandible
Leads into mandibular canal
Which nerves and blood vessels are transmitted in the mandibular canal?
Inferior Alveolar Nerve (from V3)
Inferior Alveolar Artery and Vein
Where is the mental foramen located?
What emerges from here?
Anterolateral aspect of the mandible
Mental nerve and blood vessels (from the mental canal)
What is the superior nuchal line?
Extends laterally from the external occipital protuberance
What muscle attaches to the mastoid process of the temporal bone?
The sternocleinomastoid
Where is the mastoid notch? Which muscle attaches here?
Just medial to the mastoid process
Posterior belly of digastric muscle attaches here
What are the two parts of the zygomatic bone? With which bones do they articulate?
Frontal Process (superiorly) -> with fronal bone Temporal process (posteriorly) -> with temporal bones
What structures form the zygomatic arch?
Temporal process of the zygomatic and the zygomatic process of the temporal bone
What is the area above the zygomatic arch?
What is the area below?
Temporal Fossa
Infratemporal fossa
Describe the location of the infratemporal fossa
Beneath the zygomatic arch,
deep to the ramus of the mandible
What bones form the anterior opening of the nasal cavity (piriform aperture)?
Maxilla (most)
Nasal bones
What is the sharp projection of the maxilla at the piriform aperture called?
Anterior Nasal Spine
Where is the Lateral Pterygoid Plate located? Which bone does it belong to?
In the infratemporal fossa, posterior to the maxilla
Part of sphenoid bone
Where is the pterygomaxillary fissure?
Between the Lateral Pterygoid Plate (in infratemporal fossa, posterior to maxilla) and the Maxilla bone
Where is the Pterygomaxillary fossa?
Located deeply, at the superior end of the Pterygomaxillary fissure (between maxilla and lateral pterygoid plate)
What is Fossa of the Lacrimal Sac?
Large depression at the anterior part of the medial wall of the orbit
This opens into the Nasolacrimal Canal -> leads to the nasal cavity
Infraorbital foramen - which nerve traverses this?
Infraorbital Nerve -> of maxillary division of trigeminal
Supraorbital Foramen - which nerve traverses this?
Supraorbital Nerve -> from Frontal Nerve of Opthalmic nerve from Trigeminal Nerve
Where is the apex of the orbit?
Losated Posteriorly/medially on the orbit
Where is the superior orbital fissure?
In apex of the orbit
What nerves and vessels pass through the superior orbital fissure?
(hint think nerves to muscles of eye movement…)
CNIII
CNIV
Branches of Opthalmic Nerve (CNV)
CNVI
Sympathetic Fibres from the Cavernous Plexus
Inferior Division of the Opthalmic Vein (also passes through the inferior orbital fissure)
Where is the optic canal located?
What nerve and vessel pass through here?
Just medial/superior to the superior orbital fissure
Optic Nerve (CNIII) Opthalmic Artery
What passes through the inferior orbital fissure?
Zygomatic branch of maxillary nerve
What bones contribute to the nasal septum?
Inferiorly, the VOMER bone articulates with the Anterior Nasal Spine (of the maxilla).
Superiorly, the nasal septum is formed by the PERPENDICULAR PLATE OF ETHMOID BONE
Septal cartilage fills the triangular space between these bones
Middle nasal concha is part of which bone?
Ethmoid
Roof of nasal cavity is formed by…?
Cribriform plate of ethmoid bone
What nerve passes through the foramina in the cribriform plate?
Olfactory Nerve CNI
What forms the base of the nasal cavity?
Anteriorly: Palatine Process of Maxilla
Posteriorly: Horizontal Plate of the Palatine bone
What specific part of the CNS passes through the Foramen Magnum?
Where the medulla is continuous with the spinal cord
What major arteries, and which CN enter the skull through the foramen magnum?
Vertebral Arteries
Posterior and Anterior Spinal Arteries
Accessory Nerve CNXI
What is the Basion?
What is its significance?
The most anterior part of the foramen magnum
A landmark to emasure cranial height: from basion to bregma
What are the occipital condyles?
The point of articulation of the skull onto the 1st cervical vertebra (atlas)
Where is the hypoglossal canal, and what passes through it?
Superior to the occipital condyles
Hypoglossal nerve (CNXII)
Where is the condylar canal?
May be present posterior to the occipital condyle
Which bones contribute to the Clivus?
Clivus = anterior to foramen magnum
Formed from:
Occipital bone anterior to the foramen magnum
Posterior part of the body of sphenoid
What is the Foramen Lacerum?
Located lateral to the anterior part of the Clivus
Formed at the junction between the Occipital, Temporal (apex of petrous part) and sphenoid bones.
Filled with cartilage in life*
What nerve passes through the stylomastoid foramen?
Facial Nerve
also the stylomastoid artery
What bones contribute to the jugular foramen
What vessel and nerves pass through it?
occipital and temporal
Internal Jugular vein
Meningeal Branches from Occipital and Pharyngeal Arteries
Glossopharyngral, Vagus and Accessory Nerves
What passes through the carotid canal?
Where is it?
Internal carotid artery
Just anterior to the jugular foramen
What bone (and part of that bone) forms the lateral walls of the posterior nasal apertures?
Medial Pterygoid Plates of the Sphenoid Bone
What passes through the foramen ovale?
Mandibular division of trigeminal nerve (CNV3)
What passes through foramen spinosum?
What artery is this a branch of?
Middle Meningeal Artery
from maxillary artery, which is from external carotid artery
What is a Metopic Suture?
Failure of the frontal suture to ossify (usually does so by ~4yo).
What is a fontanelle?
Why do they occur?
Fibrous tissue yet to ossify between bones of the neurocranium
Occur because neurocranium bones develop via intramembranous ossification
What is the site of the anterior fontanelle?
Bregma in v young children
Site of Posterior Fontanelle?
Lambda in v young children
Site of Sphenoidal Fontanelle
Pterion in v young children
Site of Mastoid Fontanelle
Asterion
Which bones contain air sinuses?
Ethmoid air cells
Maxillary Sinuses
Frontal Sinuses
Sphenoid Sinuses
