Osteology Of The Skull Flashcards
The skull is considered
The mandible and cranium
The cranium is considered the
Calvaria- upper dome like portion minus the facial skeleton and mandible
The Calva
Skullcap is the upper portion of the calvaria that is typically removed during autopsy
Endocranium and epicranium are continuous with each other:
Along walls of passageways through the skull- canals, foramina, fissures, and sutures.
Metopic suture
Used to describe a frontal suture that fails to close completely or partially in childhood. The frontal suture is a naturally occurring division of the skull in babies and children that normally grows together and disappears by age 8.
The paired maxillae form
Upper jaw, medial and inferior margins of orbits, and the lateral and inferior margins of the anterior nasal aperture
The nasal bones form
The bridge of the nose and the superior margins of the anterior nasal aperture
The paired zygomatic bones
Form the prominences of the cheeks and the inferior and lateral margins of the orbits
The supraorbital notch
Transmits the supraorbital nerve and vessels. The nerve is a branch of the frontal nerve, which belongs to the ophthalmic division of the trigeminal nerve (V1). The artery is derived from the ophthalmic artery, a branch of the internal carotid; the vein drains to the superior ophthalmic vein and thence to the cavernous sinus.
Infraorbital foramen
Transmits the infraorbital nerve and vessels. The nerve is a branch of the maxillary division of the trigeminal nerve. The artery is a branch from the 3rd part of the maxillary artery, a terminal branch of the carotid; the vein drains to the pterygoid venous plexus and thence to the maxillary vein.
The mental foramen
Transmits the mental nerve and vessels, which are continuations of the inferior alveolar neurovascular bundle. The nerve is therefore a branch of the mandibular division of the trigeminal. The artery is a branch of the maxillary artery from the external carotid; the vein drains to the maxillary vein
The nasion
Point of intersection of the internasal (joins nasal bones) and frontonasal (between frontal and two nasal bones) sutures
What marks the union of the left and right maxillae
Anterior nasal spine
Suture between frontal and parietal bones
Coronal suture
Suture between the left and right parietal bones
Sagittal suture
Suture between the occipital and left and right parietal bones
Lambdoidal suture
The Bregma
Point of intersection of the coronal and sagittal sutures
The location of the anterior fontanelle
The lambda
Point of intersection of the sagittal and lambdoidal sutures.
The location of the posterior fontanelle.
The parietal emissary foramina
Transmit emissary veins that are valveless and normally drain blood from the scalp into the dural sinuses in the cranium. Clinically they represent potential paths of infection leading into the brain.
The vertex
Highest point of the skull in the midline- slightly posterior to the bregma
The mastoid process
Of the temporal bone- not present at birth. It is gradually raised by the pull of the sternocleidomastoid once the infant has begun to lift its head. The process is filled with a system of air cells created by extensions of the lining of the middle ear cavity, which they remain continuous.
The pterion
Region in which the frontal, parietal and temporal bones all converge on the greater wing of the sphenoid bone. Here the wall of the temporal fossa is thin and is weakened by the presence of numerous sutures. It is easily fractured, and bone fragments may tear the underlying middle meningeal artery producing an epidural hematoma
Coronoid process
Anterior upward projection from the ramus of the mandible that gives attachment to the temporalis muscle
Mandibular notch
Lies between the coronoid and condylar processes and it gives access to the infratemporal fossa
Squamosal suture
Between the squamous portion of the temporal bone and the inferior aspect of the parietal bone
Sutures extending from the squamosal suture and what they separate
Sphenoparietal and sphenofrontal sutures
The hard palate is formed by
The maxillae- anterior 2/3
The paired palatine bones- posterior 1/3
The vomer bone
Posterior and lower part of the bony nasal septum- seen from basalis inferior
The carotid canal
Leads the internal carotid artery into the petrous portion of the temporal bone. The canal, which runs parallel to the long axis of the petrous pyramid, transmits the artery upwards into the cranial cavity towards the circle of Willis. The artery is accompanied by the internal carotid nerve, a bundle of postganglionic fibers originating from cells of the superior cervical sympathetic ganglion.
The jugular fossa
Lies on the petrooccipital suture, immediately posterior to the carotid canal. The fossa lodges the jugular bulb, the dilated upper end of the jugular vein, which communicates with the intracranial system of dural venous sinuses through jugular foramen. It also transmits the glossopharyngeal, vagus, and accessory nerves from the cranial cavity into the neck.
The stylomastoid foramen
Lower end of the facial canal in the temporal bone, lies lateral to the jugular fossa behind the base of the styloid process.
It transmits the facial nerve and the stylomastoid branch of the external carotid arterial system
Foramen spinosum
Base of the spinous process of the sphenoid bone, anterior to and across the petrosphenoid fissure from the carotid canal. The foramen transmits the middle meningeal artery branch of the external carotid arterial system into the cranial cavity. The artery is accompanied by a postganglionic plexus originating from superior cervical ganglion.
Foramen ovale
Lies anteriomedial to the foramen spinosum. It transmits both the mandibular division of the trigeminal nerve and the lesser petrosal branch of the glossopharnygeal nerve from the cranial cavity into the infratemporal fossa
Foramen lacerum
Junction of the petrous temporal, sphenoid and occipital bones. This jagged aperture does not exist in life. It is formed after death when the cartilaginous tip of the petrous temporal bone disappears. The only structures that pass through the thickness of the skull floor here are a small emissary vein and a very small branches of the ascending pharyngeal artery.
The ethmoid bone
Completes the anterior part of the floor of the anterior cranial fossa by filling a narrow, median slot in the frontal bone.
The body of the sphenoid
Central position in the middle cranial fossa, indented from above by the hypophyseal fossa to form the sella turcica
It meets the ethmoid bone and so completes the central section of the floor of the anterior anterior cranial fossa.
The cavernous sinus
Venous sinus formed within dura positioned against the body of the sphenoid bone just lateral to the sella turcica
The internal carotid artery and the abduct she nerve pass through the sinus. Embedded in the lateral wall of the sinus from superior to inferior are the oculomotor nerve, the trochlear nerve, and the ophthalmic and maxillary divisions of the trigeminal nerve
The jugum sphenoidale
Plane surface on the sphenoid bone, in front of the sella turcica, connecting the two lesser wings,and forming part of the anterior cranial fossa and the roof of the anteriomot portion of the sphenoidal sinus
The posterior edge of the jugum sphenoidale forms the anterior border of a narrow, transfer groove called
The chiasmatic groove (optic groove, prechiamatic sulcus) above and behind which lies the optic chiasma of cranial nerve II.
The tuberculum sellae
Tubercle of the sella turcica
Variable slight prominent elevation located behind the chiasmatic groove. The tuberculum sellae forms the posterior boundary of the chiasmatic groove and the anterior boundary of the hypopyseal fossa
Anterior clinic process
Posteriorly directed projection that is the medial end of the sphenoidal ridge (lesser wings); it is the attachment for the free edge of the tentorium cerebelli
Dorsum sellae
High back of the sella turcica- vertical plate of bone
Anterior surface of the dorsum faces the middle cranial fossa, its posterior surface faces the posterior cranial fossa, and its superior margin serves as a boundary between the two.
Posterior clinoid process
Project from the dorsum sellae serving as attachment sites for the tentorium cerebelli, the dural roof for the cerebellum.
The hypophyseal fossa
Holds the pituitary gland
The fossa is located in a depression in the body of the sphenoid bone
The clivus
Bony surface in the posterior cranial fossa sloping upward from the foramen magnum to the dorsum sellae. Located behind the sphenoid sinus and provides support for the pons.
Squamous portion of the temporal bone
Thin and flat- forms much of the lateral wall of the middle cranial fossa and thus contributes to the wall of skull as seen in Norma lateralis
Also includes the posterior part of the zygomatic arch, and the mandibular fossa, which lies below the floor of the middle cranial fossa
The petrous portion of the temporal bone contains
Cochlear and vestibular labryinths and provides the roof of the middle ear cavity
Cribiform plate
Horizontal part of the ethmoid bone in the floor of the anterior cranial fossa. It is thin, perforated with many small holes and is easily fractured. Forms the roof of the nasal cavity on each side, just above the olfactory epithelium, and bundles of olfactory axons pass upward through the perforations to end in the olfactory bulb, which lies on the upper surface of the plate
Optic canals
Each one opens just medial to the anterior clinoid process. It passes anterolaterally through the base of the lesser wing of the sphenoid bone to enter the apex of the orbit, transmitting the optic nerve, ensheathed by meninges, and the ophthalmic branch of the internal carotid artery. As they enter the middle cranial fossa from the orbits, the optic nerves exchange axons returning from the nasal half of each retina, forming the chiasm against the body of the sphenoid bone in front of the pituitary gland
Superior orbital fissure
Between lesser and greater wings of sphenoid bone. Through it pass the branches of the ophthalmic division of the trigeminal, the oculomotor, trochlear, and abduct some nerve, and the superior ophthalmic vein.
Foramen rotundum
Lies in the floor of the middle cranial fossa at the junction of the body and greater wing of the sphenoid. It transmits the maxillary divisions of the trigeminal from the cranial cavity into the pterygopalatine fossa.
Internal acoustic meatus
Shallow foramen in the posterior slope of the petrous ridge of temporal bone. Facial nerve and vestibulococchlear nerves pass here.
Hypoglossal canal
Passage for hypoglossal nerve- innervates the muscles that move the tongue
Crista galli
Sail shaped vertical plate of bone projecting upward along the midline from the cribiform plate. Continuous below wit the bony nasal septum and anchors the anterior end of the falx cerebri.
Frontal crest
Internal surface of frontal bone has a ridge with a midline sagittal sulcus, which is related to the superior sagittal sulcus. The margins of the frontal crest afford attachment of the falx cerebri.
The arcuate eminence
Distinct, rounded prominence on the superior surface of the petrous temporal bone. It sits about half way up the anterior slope of the bone. This rounded eminence marks the positions of the anterior semicircular canal in the inner ear
Tegmen tympani
Thin plate of bone which separates the middle cranial fossa from the tympanic cavity. It is situated on the anterior slope of the petrous portion of the temporal bone close to where it meets the squamous portion. Right in front of the arcuate eminence.
Trigeminal depression
Floor of middle cranial fossa. This is where the trigeminal ganglion resides. Can see the ophthalmic division passing through the superior orbital fissure, the maxillary division passing through the foramen rotundum, and the mandibular division passing through the foramen ovale.
Petrous ridge serves as attachment for
Tentorium cerebelli
Grooved for the superior petrosal sinus
Internal occipital crest
Attachment for falx cerebri. In this attachment margin is the occipital sinus
Cruciform eminence
Bony cross like elevation on the internal aspect of the squamous portion of the occipital bone. Formed by the intersection of the groove for the transverse sinuses and the internal occipital crest. The internal occipital protuberance is at the center of the cross
Wormian bones
Intrasutural bones can form between the cranial sutures formed by the bones of the cranial vault. When these separate centers of ossification occur in the lambdoidal suture, where they are typically found, they are called Wormian bones. They are innocuous and should not be interpreted as skull fracture lines during imaging of skull bones.
