Chapter 1 - Neurocranium

Question 1

Two parts of the cranium (and their purpose)

Answer 1

Neurocranium (above orbits, encases brain) and Viscero/Splanchocranium (Midface, nasal passages and oral cavity)

Question 2

Neurocranium is divided in two two parts

Answer 2

1. Calvaria or cranial vault

2. Cranial base/floor

Question 3

Calvaria bones and embryonic formation

Answer 3

Skull roof bones are frontal - parietal - temporal (squamous) - and occipital bones. These bones are formed by intramembranous ossification. This means that membranes of mesenchymal cells around the brain becomes osteoblasts directly that secretes a matrix that becomes bone when calcified. These islands of bone expand radially during infancy creating fontanelles that eventually fuse at suture lines.

Question 4

What is craniosynostosis? How does this affect skull growth?

Answer 4

Premature fusions of cranial bones. Causing expansion perpendicular to the fused suture line.

Question 5

Name the sutures and their placement on the skull

Answer 5

Sagittal ( along midlines ant-post)

Coronal (separates frontal from parietal bones)

Lambdoid (separates parietal and occipital bones)

Bregman = sagittal and coronal intersection

Lambda = sagital and lambdoid intersection

Question 6

What is the pterion and asterion?

Answer 6

These are confluence points of multipl bones.

Pterion is the confluence of temporal, parietal, sphenoidal, frontal bones anteriorly. The middle meningeal artery runs through this point. If traumatized it can cause a fatal epidural hematoma. (H shaped)

Asterion is more posterior confluence of parietal temporal and occipital bones.

Question 7

What are bones of the cranial base/floor?

Answer 7

Frontal, Ethmoidal, Sphenoidal, Temporal, and Occipital nones anteirroly to posteriorly.

These form the anterior, middle and posterior cranial fossa.

Question 8

Anterior cranial fossa compontents

Answer 8

Frontal, Ethmoidal, and Sphenoid bones. Contains Cerebrum.

Foramen Cecum - between frontal and ethmoid bones near crista gali

Ethmoid bone creates the CRISTA GALI which attaches to the CEREBRAL FALX (that separates the hemispheres of the brain. The CRIBIFORM PLATES can be seen laterally to the Crista Gali where CN 1 enters (sensory smell).

Sphenoid bone lesser wings make up the posterior aspect of the anterior cranial fossa. They form the anterior clinoid processes and jugum.

ANTERIOR CLINOID PROCESSES attaches to cerebellar tentorium which separates the cerebellum from cerebrum.

JUGUM is a flattened process that support CN 1/olfactory tracts

Question 9

Middle Cranial Fossa components

Answer 9

Greater wings and body of Sphenoid bone and Temporal bones.

This fossa contains the temporal lobes laterally.

Centrally it contains the SELLA TURCICA ( body of sphenoid bone). The HYPOPHYSEAL FOSSA in the center of this structure contains the PITUITARY GLAND. Posterior potion of the sella turcica called DORSUM SELLA contains the POSTERIOR CLINOID PROCESSES which attach to the cerebellar tentorium.

This also contains most of the cranial nerve foramen.

Lateral to this fossa is the Cavernous Sinus

Question 10

What is contained in the Cavernous Sinus?

Answer 10

Cavernous sinus is a drainage point of the superior ophthalmic vein and superficial middle cranial vein. OTOM pneumonic
A
C
OTOM (Oculomotor/III, Trochlear/IV, Opthalmic/V1, Maxillary/V2) which is contained in the lateral wall of the sinus.

Abducens Nerve (CN VI) contained in cavernous sinus

Carotid Artery (Internal) contained in cavernous sinus

Question 11

Name the foramen of the middle cranial fossa and the bony location

Answer 11

Moving from central/anteriorly to posterior laterally

Optic Canal - lesser wing of sphenoid (just under anterior clinoid processes)

Superior orbital fissure - gap between greater and lesser wings of sphenoid

Foramen rotundum - Greater wing of sphenoid
Foramen ovale - Greater wing of sphenoid
Foramen spinosum - Greater wing of sphenoid

Foramen Lacerum - gap between sphenoid and temproal bones

Question 12

Optic Canal components

Answer 12

CN II (Sensory) and ophthalmic artery (ICA branch) ( provides vision) and postganglionic sympathetic fibers

Question 13

Superior orbital fissure components

Answer 13

CN III (Motor), IV (M), V1 (Sensory), VI(M) and ophthalmic vein (drains blood from orbit to cavernous sinus) and postganglionic sympathetic fibers

Question 14

Foramen Rotundum components

Answer 14

CN V2 travels through foramen rotundum to pterygopalatine fissure

Question 15

Foramen Ovale components

Answer 15

CN V3 and with the lesser petrosal nerve (CN IX) travel through the foramen ovale to the infratemporal fossa

Question 16

Foramen Spinosum components

Answer 16

Middle Meningeal Artery travels from the infratemproal fossa through the foramen spinosum to provide vasculature to the brain.

It also contains some CN V meningeal branches (Sensory)

Question 17

Foramen Lacerum components

Answer 17

Short vertical tunnel blocked off by cartilage inferiorly.

ICA travels through it partly then turns to access the cavernous sinus. ( it enters via a lateral opening from external carotid canal)

Greater petrosal nerve (CN VII) travels from superior opeing then joins the deep petrosal nerve via a lateral opening to the pterygoid canal.

Question 18

Posterior Cranial Fossa Components

Answer 18

Sphenoid, Parietal, Temporal, and Occipital bones.

Contains Cerebellum and brainstem,
Clivus (flat surface of sphenoid and occipital bones anterior to foramen magnum and posterior to dorsum sella)
Foramen Magnum (occipital bone)
Hypoglossal canals(Occipital bone)
Jugular foramen (gap between temporal and occipital bones)
Internal Auditory Meatus/Canal

Question 19

Foramen Magnum components

Answer 19

Vertebral arteries and Spinal Cord, spinal component of CN XI, and anterior and posteiror spinal arteries.

Where brain stem ends and spinal cord begins. Vertebral arteries pass through vertebral foramena of vertebrae and vertebral canal.

Question 20

Clivus components

Answer 20

Contains the pons ( anterior portion of brainstem)

Question 21

Hypoglossal canal compontents

Answer 21

contains CN XII (M) and branches of upper cervical spinal nerves (S)

Damage to CN XII causes tongue protrusion to affected side. Motor to all tongue muscles except palatoglossus (CN 9 and 11)

Question 22

Jugular Foramen components

Answer 22

Internal jugular vein, CN IX, CN X, and CN XI

Glossopharyngeal provides Sensory and Motor to tongue and pharynx - motor to stylopharyngeous and pharyngeal muscles. Parasympathetic on parotid gland. innervates carotid body and sinus. Taste to posterior third of tongue.

Vagus provides parasympathetic, Motor to pharyngeal, laryngeal (talking) and palatal muscles (swallowing) and Sensory to skin and posterior cranial fossa (sensory). Taste to epiglottis. Parasympathetic innervation to thorax and abdomen.

Accessory nerve provides Motor to SCM and trapezius

Question 23

Internal Auditory Meatus/canal (Stylomastoid foramen)

Answer 23

CN VII and CN VIII enter this canal

CN VII = Motor to face, Parasympathetic to lacrimal and salivary glands ( not parotid), and sensory (taste) and extis at stylomastoid foramen

CN VIII = sensory hearing and vestibular system and ends at inner ear

Question 24

Dura Mater structure

Answer 24

Bilaminar membrane with periosteal layer attachment to skull and meningeal layer confluent with spinal cord dural mater. these layers are fused throughout EXCEPT

1. Dural Infoldings (Falx cerebri and cerebellar tentorium)
2. Dural Sinuses (Venous blood drains to IJV which exits via jugular foramen.)

Question 25

Foramen Cecum

Answer 25

Anterior start of superior sagittal sinus with a vein that runs from the nasal cavity.

Question 26

Blood drainage from brain

Answer 26

Superior sagittal sinus runs along midline to confluence of sinuses.

Superior ophthalmic vein runs through the superior orbital fissure and middle cranial vein drain to the cavernous sinus which drains to jugular foramen via petrosal sinuses (Sup and inf.)

Confluence drains laterally through transverse sinuses to sigmoid sinuses ( S shaped) which become IJV at the jugular foramen.

Question 27

Carotid canal components

Answer 27

ICA from neck to brain and opens to wall for rotundum lacerum.

Question 28

External skull components not noted internally

Answer 28

Carotid Canal
Occipital Condyle, 
Stylomastoid foramen
Styloid Process
Mastoid process

Question 29

Occipital Condyles (Atlanto-Occipital Joint)

Answer 29

Are lateral to foramen magnum and articulate with first cervical vertebrae forming the Atlanto-Occipital Joint

Question 30

CN V motor vs sensory

Answer 30

both - muscles of mastication and sensory

Question 31

CN III motor vs sensory

Answer 31

both - IOM and accomodation via pupillary constriction, raises eyelid via levator palpabrae superioris

Question 32

CN VII motor vs sensory

Answer 32

both - motor to orbicularis oculi to close eye and all facial expression muscles plus stapedius muscle, stylohyoid muscle, posterior belly of digastric.

Parasympathetic influence on lacrimal and salivary glands. Taste to anteriro two thirds of tongue chroda tympani.