Osteology Of The Skull

Question 1

The skull is considered

Answer 1

The mandible and cranium

Question 2

The cranium is considered the

Answer 2

Calvaria- upper dome like portion minus the facial skeleton and mandible

Question 3

The Calva

Answer 3

Skullcap is the upper portion of the calvaria that is typically removed during autopsy

Question 4

Endocranium and epicranium are continuous with each other:

Answer 4

Along walls of passageways through the skull- canals, foramina, fissures, and sutures.

Question 5

Metopic suture

Answer 5

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.

Question 6

The paired maxillae form

Answer 6

Upper jaw, medial and inferior margins of orbits, and the lateral and inferior margins of the anterior nasal aperture

Question 7

The nasal bones form

Answer 7

The bridge of the nose and the superior margins of the anterior nasal aperture

Question 8

The paired zygomatic bones

Answer 8

Form the prominences of the cheeks and the inferior and lateral margins of the orbits

Question 9

The supraorbital notch

Answer 9

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.

Question 10

Infraorbital foramen

Answer 10

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.

Question 11

The mental foramen

Answer 11

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

Question 12

The nasion

Answer 12

Point of intersection of the internasal (joins nasal bones) and frontonasal (between frontal and two nasal bones) sutures

Question 13

What marks the union of the left and right maxillae

Answer 13

Anterior nasal spine

Question 14

Suture between frontal and parietal bones

Answer 14

Coronal suture

Question 15

Suture between the left and right parietal bones

Answer 15

Sagittal suture

Question 16

Suture between the occipital and left and right parietal bones

Answer 16

Lambdoidal suture

Question 17

The Bregma

Answer 17

Point of intersection of the coronal and sagittal sutures

The location of the anterior fontanelle

Question 18

The lambda

Answer 18

Point of intersection of the sagittal and lambdoidal sutures.
The location of the posterior fontanelle.

Question 19

The parietal emissary foramina

Answer 19

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.

Question 20

The vertex

Answer 20

Highest point of the skull in the midline- slightly posterior to the bregma

Question 21

The mastoid process

Answer 21

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.

Question 22

The pterion

Answer 22

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

Question 23

Coronoid process

Answer 23

Anterior upward projection from the ramus of the mandible that gives attachment to the temporalis muscle

Question 24

Mandibular notch

Answer 24

Lies between the coronoid and condylar processes and it gives access to the infratemporal fossa

Question 25

Squamosal suture

Answer 25

Between the squamous portion of the temporal bone and the inferior aspect of the parietal bone

Question 26

Sutures extending from the squamosal suture and what they separate

Answer 26

Sphenoparietal and sphenofrontal sutures

Question 27

The hard palate is formed by

Answer 27

The maxillae- anterior 2/3

The paired palatine bones- posterior 1/3

Question 28

The vomer bone

Answer 28

Posterior and lower part of the bony nasal septum- seen from basalis inferior

Question 29

The carotid canal

Answer 29

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.

Question 30

The jugular fossa

Answer 30

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.

Question 31

The stylomastoid foramen

Answer 31

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

Question 32

Foramen spinosum

Answer 32

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.

Question 33

Foramen ovale

Answer 33

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

Question 34

Foramen lacerum

Answer 34

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.

Question 35

The ethmoid bone

Answer 35

Completes the anterior part of the floor of the anterior cranial fossa by filling a narrow, median slot in the frontal bone.

Question 36

The body of the sphenoid

Answer 36

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.

Question 37

The cavernous sinus

Answer 37

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

Question 38

The jugum sphenoidale

Answer 38

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

Question 39

The posterior edge of the jugum sphenoidale forms the anterior border of a narrow, transfer groove called

Answer 39

The chiasmatic groove (optic groove, prechiamatic sulcus) above and behind which lies the optic chiasma of cranial nerve II.

Question 40

The tuberculum sellae

Answer 40

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

Question 41

Anterior clinic process

Answer 41

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

Question 42

Dorsum sellae

Answer 42

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.

Question 43

Posterior clinoid process

Answer 43

Project from the dorsum sellae serving as attachment sites for the tentorium cerebelli, the dural roof for the cerebellum.

Question 44

The hypophyseal fossa

Answer 44

Holds the pituitary gland

The fossa is located in a depression in the body of the sphenoid bone

Question 45

The clivus

Answer 45

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.

Question 46

Squamous portion of the temporal bone

Answer 46

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

Question 47

The petrous portion of the temporal bone contains

Answer 47

Cochlear and vestibular labryinths and provides the roof of the middle ear cavity

Question 48

Cribiform plate

Answer 48

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

Question 49

Optic canals

Answer 49

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

Question 50

Superior orbital fissure

Answer 50

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.

Question 51

Foramen rotundum

Answer 51

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.

Question 52

Internal acoustic meatus

Answer 52

Shallow foramen in the posterior slope of the petrous ridge of temporal bone. Facial nerve and vestibulococchlear nerves pass here.

Question 53

Hypoglossal canal

Answer 53

Passage for hypoglossal nerve- innervates the muscles that move the tongue

Question 54

Crista galli

Answer 54

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.

Question 55

Frontal crest

Answer 55

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.

Question 56

The arcuate eminence

Answer 56

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

Question 57

Tegmen tympani

Answer 57

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.

Question 58

Trigeminal depression

Answer 58

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.

Question 59

Petrous ridge serves as attachment for

Answer 59

Tentorium cerebelli

Grooved for the superior petrosal sinus

Question 60

Internal occipital crest

Answer 60

Attachment for falx cerebri. In this attachment margin is the occipital sinus

Question 61

Cruciform eminence

Answer 61

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

Question 62

Wormian bones

Answer 62

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.