Skull Flashcards
State the functions of the skull
Supports and protects the brain; isotropic resistance to impact by dispersing forces
Describe the layers of the skull
External (outer) table and internal (inner) table with diploe in the middle (bubbly less solid structure)
How can the skull be split in to two sections?
Neurocranium: aspects supporting and containing the brain; Viscerocranium: facial aspects that aid in talking, breathing etc
What is excess cranial bone called?
Wormian bones which do not have names but are small amounts of bone that sit between the sutures
What lies between cranial bones?
Sutures: joints between cranial lines which will not move (with exception to mandible)
Name the outer and inner surfaces of the skull
Ectocranial (outside) and endocranial (inside).
How can the neurocranium be split?
Membranous/dermatocranium: mainly the flat bones of the skull cap e.g. frontal & parietal - formed through intramembranous ossification ; Cartilaginous/chondrocranium: More complex structures e.g. sphenoid and ethmoid which border on mixing with viscerocranium - formed by endochondral ossification (start as cartilage)
Name the bones of skull
Cranial: frontal, parietal (x2), occipital, temporal (x2), ethmoid, sphenoid ; Facial: maxillae (x2), palatines (x2), nasals (x2) lacrimals (x2), zygomatics (x2), vomer, inferior nasal conchae (x2), manidble ; Ear ossicles: malleus, incus, stapes.
Name the type of suture that is present in childhood but can stay as a non-metric trait in adults
Metopic suture
Name the sutures of the skull
(Synchondroses): coronal, sagittal, squamous (overlapping), lambdoid, lambda, bregma, pterion, frontomaxillary, frontonasa, frontozygomatic, intermaxillary, median palatine, occipitomastoid, parietomastoid, sphenofrontal, sphenooccipital, sphenoparietal, sphenosquasomal, sphenozygomatic, temporozygomatic, transverse palatine, zygomaticomaxillary, tempomandibular joint, atlanto-occipital joint
Name the 12 cranial nerves and their type of nerve function
CNI - Olfactory (S) ; CNII - Optic (S) ; CNIII - Oculomotor (M) ; CNIV - Trochlear (M) ; CNV - Trigeminal (S&M) ; CNVI - Abducens (M) ; CNVII - Facial (S&M) ; CNVIII - Vestibulocochlear/Auditory (S) ; CNIX - Glossopharyngeal (S&M); CNX - Vagus (S&M) ; CNXI - Accessory (M) ; CNXII - Hypoglossal (M)
Which nerve has 3 branches and what are they?
CNV - Trigeminal (S&M): 1 - Ophthalmic, 2 - Maxillary, 3 - Mandibular.
Which bones are part of the neurocranium?
Frontal, parietal, temporal, occipital, sphenoid, ethmoid
What bones does frontal articulate with?
Parietals, zygomatics, lacrimals, nasals, maxillae, sphenoid, ethmoid
Name and detail the eminences at the front of the frontal bone
Frontal bosses: more significant in females ; marks ossification centres of frontal bone
Name the features just above the orbits
Glabella / supraorbital ridge : of the frontal bone (brown ridge)
Describe the temporal line
Attachment site of temporalis formed by mastication; (temporalis will run through the zygomatic foramen to the coronoid process of the mandible) ; runs across the frontal and parietal bones on either side
Describe the supraorbital margin and a feature within it
Feature of the frontal bone directly above the orbitals superior to the eyes ; supraorbital notch or foramen (if closed) is found here
Describe the nasal spine
The inferior aspect of the frontal bone that comes down to join the nasals
What part of the frontal bone articulates to the zygomatic bones on either side?
Zygomatic processes
Describe the frontal sinuses
Located at the medial inferior aspect of the front bone; air cells that are pockets within the bone; can be used for ID in forensics
Name and detail the structure that runs down the internal midline of the frontal bone
Frontal crest: Anchors the flax celebri (fold of the dura mater (outermost layer of brain surrounding)) ; runs between the sinuses as a slightly raised line ; is continuous with the sagittal sulcus
Describe sagittal sulcus
(Sagittal sinus) for venous drainage, is continuous with the frontal crest of the frontal bone and continues on to the parietal bones
Describe arachnoid granulations / fovae
Run on the internal surface of the frontal and parietal bones along the top on either side of the sagittal sulcus - they are small holes left by the membrane pushing out leading to resorption of the bone
Where does the ethmoid bone articulate with the frontal bone?
Ethmoid notch, either side of the frontal crest, medial to sinuses
What do the parietal bones articulate with?
Eachother, sphenoid, occipital, temporal, frontal
Name and detail the protrusions of the parietal bones
Parietal bosses/eminences: similar to those of frontal, lie on either side and are slightly posterior - can be felt
Can foramen be found on the parietal bones?
Yes. Parietal foramen / emissary foramina - on posterior superior portion on either side - not always present.
What are parietal striae?
Lines found on the temporal aspect of parietal bones formed from the friction at the squamal suture sitting underneath the overlap
What lies on the internal surface of parietal bones?
Meningeal grooves are anteriorly close to the coronal suture and travel from inferior to superior in a posterior direction. Bregma inner table protrudes more than outer table
What do the temporal bones articulate with?
Parietal, sphenoid, occipital. zygomatics, mandible
How can the temporal bone be split?
Squamous portion: flatter thinner part ; petrous/mastoid portion: solid, thick bone which houses ear organs
Describe two features of and two attachment to the mastoid process
Mastoid foramina: posterio-inferior for occipital veins and arteries ; Supramastoid crest ; Mastoid notch: medial attachment for digastric muscle (to digastric fossa of mandible and hyoid for jaw movement) ; attachment for sternocleidomastoid (head & neck movement - lateral flexion)
Name and describe two key features of the petrous part of the temporal bone relating to the ear
The external and internal auditory meatus. Internal points posteriorly. Suprameatal crest lies superior to external. external is posterior, internal is anterior
Where does temporalis attach to the temporal bone
Supramastoid and suprameatal crests
Where on the temporal bone does the mandible articulate?
Glenoid / mandibular fossa at the temporomandibular joint
Name three processes of the temporal bone and describe them.
Mastoid process: attachment for sternocleidomastoid ; Zygomatic process: attaches to the temporal process of the zygomatic to create the zygomatic arch; styloid process: often broken off post-mortem, lies inferior to the mandibular fossa, is called “eagle” if it is really long.
What foramen on the temporal bone houses the stylomastoid artery and what cranial nerve also passes here?
Stylomastoid foramen - passage for CN VII (Facial)
What groove lies posterior to the stylomastoid foramen (internal surface)?
Groove for transverse sinus which continues onto the occipital bone
Which fossa lies antero-medial to the styloid process and what nerves does it carry?
Jugular fossa creates jugular foramen with occipital bone for CN IX, X, XI.
What bones does the occipital articulate with?
Parietals, temporals and sphenoid
What is the flat aspect of the occipital bone called?
The occipital squama
What part of the occipital bone lies between the foramen magnum and the outer edges of the bone?
Pars lateralis - this is unfused in children
What aspect of the occipital bone articulates with sphenoid?
Basilar synchondrosis
What aspect of the occipital bone articulates with C1?
Occipital condyles
What parts of the occipital bone makes the border of the foramen magnum and what does this hold?
Squama, pars lateralis and basilar synchondrosis - holds the spinal cord
What protrudes posteriorly on the occipital bone and what attaches here?
External occipital protuberance roughly halfway between neck and top of head - attachment for ligamentum nuchae from C7 - larger in males.
Describe the nuchal lines and their muscular attachments
Superior: Trapezius (from clavicle and scapula - elevates and depresses scapula) ; Inferior: Rectus capitus posterior (from axis - extends and rotates head) ; Between superior and inferior: Semispinalis capitis (from transverse processes C4-7, T1-7 - extends and rotates head)
Name and describe the two sulcus’s of the occipital bone and what they create on the endocranial surface
Transverse sulcus for transverse sinus (venous drainage of the brain) ; sagittal sulcus for sagittal sinus (continues to parietals) creating the cruciform eminence at the middle of the cross creating 4 fossae - superior for cerebrum and inferior for cerebellum
What notch of the occipital meets with the temporal bone to form a foramen and what passes through this foramen?
Jugular notch on side of pars lateralis - forms jugular foramen for the jugular vein as well as CN IX (glossopharyngeal), CN X (vagus) and CN XI (accessory)
Name CNXII and where it passes (specify the bone)
Hypoglossal nerve passes through the hypoglossal canal on the rim of the foramen magnum of occipital
What fossas exist slightly posterior to the occipital condyles?
Condylar fossa
What bones does sphenoid articulate with?
Frontal, parietal, ethmoid, zygomatics, temporal, occipital, palatine, vomer
Name the major bony features of the sphenoid bone
Greater wings, lesser wings, basilar synchondrosis, medial and lateral pterygoid plates
What do the greater wings of sphenoid articulate with?
Frontal, parietals and temporals
Where do the lesser wings of the sphenoid lie?
Internally and superiorly
What bone does the basilar synchondrosis of the sphenoid meet?
Occipital
Name the articulations of the pterygoid plates and their muscular attachments/
Each pair articulates anteriorly with palatines, posteriorly with maxilla (medial plate is part of the nose). Lateral plates act as surface area for attachment for medial and lateral pterygoid muscles (from mandible - opening and closing mouth)
What lies between the pterygoid plates?
Pterygoid fossa - lies inferio-posteriorly and opens posteriorly
What feature lies within the anterior body of the sphenoid bone?
Sphenoid sinus
Describe the “Turkish Saddle” of the sphenoid bone and the processes that surround it.
Sella turcica is surrounded by clinoid processes on four corners - these can sometimes bridge to form foramen. They are either anterior or posterior.
What structure holds the pituitary gland and where is it?
The pituitary fossa of the sphenoid bone which sits between sella turcica and basilar synchondrosis.
Detail the cranial nerve passages in the sphenoid bone.
Optic foramen/canal : CNII OPTIC - sits anteriomedially to sella turcica just inferior to clinoid processes ; Superior orbital fissure : CNIII OCULOMOTOR, CN IV TROCHLEAR, CNV(1) OPHTHALMIC, CN VI ABDUCENS - sits inferior to lesser wing between greater and lesser ; Foramen rotundum: CNV(2) MAXILLARY ; Foramen ovale: CNV(3) MANDIBULAR.
Name two non-cranial foramen of the sphenoid and what structures they carry
Foramen spinosum - middle meningeal artery ; foramen lacerum (formed from borders of sphenoid, occipital and temporal) - carotid artery
How many bones does ethmoid articulate with?
15
How does this ethmoid sit in relation to nasals and frontal?
Sits posterior to nasals and fits into the ethmoid groove of frontal.
What kind of surface does the ethmoid bare making it useful for smell?
Pneumatised tissue (lots of holes) with a large surface area.
Describe the superior aspect of the ethmoid bone
Crista galli is the superior process which sits in ethmoid groove of the frontal bone. It sits above the cribriform plate which has many tiny holes - ethmoid sinuses - for the olfactory nerve (CN I) to go through after splitting into branches.
What structures lie laterally and inferiorly within the ethmoid bone?
Lamina orbitalis / orbital plates and perpendicular plate (inferior process)
Describe the position of the nasal concha
Part of the ethmoid bone - superior and middle nasal concha lie on either side of the perpendicular plate (inferior nasal concha below)
What bones do the zygomatics articulate with?
Frontal, temporals, maxillae, sphenoid
Describe the articulation points of the zygomatics.
Maxillary process: most anterior border ; Fronto-sphenoidal process: most superior process (tip articulates with frontal, posterior articulates with sphenoid) ; Temporal process: attaches zygomatic process of temporal bone to form zygomaticotemporal suture and zygomaticarch.
Name the foramen of the zygomatic bone
Zygomatico-orbital foramen: within orbital border ; zygomatico-facial foramen: anterior bone just inferior to orbit ; zygomatico-temproal foramen: posterior aspect of fronto-sphenoidal process (CNVII - facial)
What bones do the maxillae articulate with?
Zygomatics, nasal, frontal, lacrimals, palatines, spehnoid, ethmoid
Describe some of the processes of the maxillae
Zygomatic process (lateral) ; frontal process (pointed bit superiorly that forms parts of side of the nasal aperture) ; palatine process (anterior 2/3 of palate and floor of nasal cavity which joins to palatines) ; Alveolar process (bit that attaches to the teeth - alveolus = tooth socket)
Detail the ANS
Anterior nasal spine sits as the most inferior/anterior part of the nasal aperture of the maxilla
What eminence forms on the maxillae?
The canine eminence over the canine teeth - created by the large single roots of the canine which is much bigger than the surrounding roots.
What foramen sits inferior to the orbit and what does it carry?
Infraorbital foramen of the maxillae - carries the infraorbital artery and vein
What foramen sits anterior and inferior on the maxillae?
Incisive foramen/canals - blood supply to the palate
What large structure of the maxillae sits posteriorly and superior to the palate?
Maxillary sinus
What suture lies between the maxillae and the palatine bones?
Transverse palatine suture
What foramen lie on the horizontal plate of the palatine bone?
Greater (anterior) and lesser (posterior) palatine foramen - carry arteries and nerves.
What aspect of the palatine bone is often broken?
Perpendicular plate
What part of the palatine forms the roof of the mouth?
Horizontal plate
What bony feature lies most laterally and inferiorly in the palatine
Pyramidal process and it’s tubercle
What bones do the nasals articulate with?
Each other, frontal (superiorly) and maxillae (laterally)
Describe the structure of the nasals
Round and narrow first then widen and flare; lateral margins come down further than medial margins leaving nose to be mostly cartilage
What foramen is present on the nasals
Nasal foramen - tiny hole midway down
What bones do the lacrimals articulate with?
Maxillae, ethmoid, frontal
Name a feature of the lacrimal
Lacrimal groove
What bones dos the inferior nasal concha articulate with?
Ethmoid, maxillae, lacrimals, palatines
What nasal conchae are individual bones or not?
Inferior is own bone, superior and middle are part of ethmoid bone.
Name a feature of the inferior nasal concha
Groove
What bones does the vomer articulate with?
Sphenoid, ethmoid, palatines, maxillae
Describe the structure and function of vomer
Thin bone that splits posteriorly and is covered in sensitive tissue that aids in smelling
Name the main features of the vomer bone
Ala (wings) that open posteriorly ; vomerine groove
Name the main features of malleus
Head (articulates with incus); neck, manubrium (end of bone - no articulation)
Name the main features of incus
Anterior surface (for malleus), body, shortcrus (projection of body with no articulation), longcrus (projection leading to stapes), lenticular process (process off longcrus close to stapes)
Name the main features of stapes
Head (articulates with incus), anterior and posterior crus, base (no articulation)
What bones does the mandible articulate with?
Temporal and hyoid (indirectly)
Describe the main features of the mandible.
Body (corpus), mentum/mental protuberance (chin) ramus (up the side), coronoid process (temporalis), mandibular condyle (posterior to coronoid)
What lies between the coronoid process and mandibular condyle?
Mandibular fossa
Name and describe the angle between the ramus and body of the mandible including sexing traits and muscular attachments
Gonial angle. Angle degree used for sexing and level of gonial flaring. Attachment for masseter (to zygomatic process - chewing)
What feature lies at the mid point of the mandible on the posterior side and what muscle attaches here?
Mental spine - attachment for genioglossus (protruding/sticking tongue out)
What foramen is present on the mandible?
Mental foramen carrying branches of trigeminal (CNV) - can occur as two holes as a non-metric trait
What groove and line lies on the internal ramus of the mandible and what are their functions?
Mylohyloid groove acts as a passage for mylohyoid vessels and trigeminal (CN V) nerve (continues internally to mental foramen).
Mylohyoid line continues anteriorly from groove as a crest acting as an attachment for mylohyoid muscle (elevates hyoid, raises floor of mouth and tongue for swallowing and speaking)
What fossae border the mylohyoid line and what are their functions?
Sublingual (superiorly) and submandibular (inferiorly) to carry salivary glands.
