Chapter 1 - Neurocranium Flashcards
Two parts of the cranium (and their purpose)
Neurocranium (above orbits, encases brain) and Viscero/Splanchocranium (Midface, nasal passages and oral cavity)
Neurocranium is divided in two two parts
- Calvaria or cranial vault
2. Cranial base/floor
Calvaria bones and embryonic formation
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.
What is craniosynostosis? How does this affect skull growth?
Premature fusions of cranial bones. Causing expansion perpendicular to the fused suture line.
Name the sutures and their placement on the skull
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
What is the pterion and asterion?
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.
What are bones of the cranial base/floor?
Frontal, Ethmoidal, Sphenoidal, Temporal, and Occipital nones anteirroly to posteriorly.
These form the anterior, middle and posterior cranial fossa.
Anterior cranial fossa compontents
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
Middle Cranial Fossa components
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
What is contained in the Cavernous Sinus?
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
Name the foramen of the middle cranial fossa and the bony location
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
Optic Canal components
CN II (Sensory) and ophthalmic artery (ICA branch) ( provides vision) and postganglionic sympathetic fibers
Superior orbital fissure components
CN III (Motor), IV (M), V1 (Sensory), VI(M) and ophthalmic vein (drains blood from orbit to cavernous sinus) and postganglionic sympathetic fibers
Foramen Rotundum components
CN V2 travels through foramen rotundum to pterygopalatine fissure
Foramen Ovale components
CN V3 and with the lesser petrosal nerve (CN IX) travel through the foramen ovale to the infratemporal fossa
Foramen Spinosum components
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)
Foramen Lacerum components
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.
Posterior Cranial Fossa Components
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
Foramen Magnum components
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.
Clivus components
Contains the pons ( anterior portion of brainstem)
Hypoglossal canal compontents
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)
Jugular Foramen components
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
Internal Auditory Meatus/canal (Stylomastoid foramen)
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
Dura Mater structure
Bilaminar membrane with periosteal layer attachment to skull and meningeal layer confluent with spinal cord dural mater. these layers are fused throughout EXCEPT
- Dural Infoldings (Falx cerebri and cerebellar tentorium)
- Dural Sinuses (Venous blood drains to IJV which exits via jugular foramen.)
