Intracranial Anatomy Flashcards
Neurocranium Components
Cranial vault and cranial base
Cranial vault
- Calvaria or membranous neurocranium
- Develops from intramembranous ossification
Cranial base
- Basicranium or chondral neurocranium
- Develops from endochondral ossification
Viscerocranium
- Face and mandible
- Develops from branchial arches
Types of bone in cranial vault
- Compact bone of inner and outer tables
- Diploë: spongy bone in the middle
Cranial Sutures
- Fibrous joint: held together by Sharpey’s fibers (collagen type III)
- Sutural (Wormian) bones: small, irregular bones that develop within sutures
Cranial vault sutures
- Coronal
- Lambdoid
- Metopic/frontal (fuses at 9 months)
- Pterion
- Sagittal
- Squamosal
Facial (palatal) sutures
- Intermaxillary
- Transverse palatine
Emissary veins
External veins that drain through diploic veins to internal dural sinuses. These are a potential route of infection from the scalp into the cranial vault.
Cranial sinuses
- Frontal
- Ethmoidal
- Sphenoidal
- Maxillary (Antrum)
Also: mastoid air cells
Semilunar hiatus
Drains frontal, maxillary, and anterior ethmoidal sinuses into nasal cavity
Posterior ethmoidal and sphenoidal sinuses drain into…
nasopharynx
Maxillary Sinus (Antrum)
- contains the CN V2, maxillary nerve (GSA to upper teeth, palate, nasal cavity)
- Maxillary dental roots can project into sinus
Meninges from Superficial to Deep
- Dura mater
- Arachnoid mater
- Pia mater
Arterial supply to meninges
middle meningeal artery from maxillary artery
Innervation of meninges
- anterior and middle cranial fossae- CN V
- Posterior cranial fossa- CN IX, X C1-3
Dura mater
- Endosteal layer (ends at foramen magnum)
- Meningeal layer (continues to spinal cord)
- Dural sinuses (venous drainage for intracranial region) form between layers
- Forms folds around parts of the brain (e.g. tentorium cerebelli, falx cerebri)
- Dural folds
- Falx cerebri
- Tentorium cerebelli
- Formed by the meningeal layer of dura mater
- Falx cerebri separates the left and right cerebral hemispheres
- Tentorium cerebelli separates the cerebru, and cerebellum
Arachnoid mater
Forms arachnoid granulations, which allow cerebrospinal fluid (CSF) to enter dural sinuses and return to systemic circulation
Pia mater
- impermeable to fluid, encloses CSF around brain
- forms perivascular spaces that act as brain’s lymphatic system
Meningeal Spaces Chart
Dural Sinuses
- Venous drainage for the cranial cavity
- Returns CSF to circulation
- Lymphatic system runs along sinuses inside skull
Dural Sinuses: Superior and Inferior sagittal sinuses
in falx cerebri
Dural Sinuses: Straight sinus
at junction of falx cerebri and tentorium cerebelli
Dural Sinuses: transverse sinus
in tentorium cerebelli
Dural Sinuses: Sigmoid sinus
drain to internal jugular vein
Dural Sinuses: Cavernous sinus
surrounds internal carotid artery
Venous blood exits skull through:
- internal jugular vein (sigmoid sinus)
- vertebral veins (vertebral venous plexuses)
- Maxillary vein (cavernous sinus and pterygoid venous plexuses)
Cranial base: Foramen (pl. foramina)
holes where cranial nerves and vasculature enter/exit the skull
Cranial base: fossa (pl. fossae)
- depression in cranial base
- anterior cranial fossa: frontal lobes, olfactory bulbs
- middle cranial fossa: temporal lobes, pituitary gland
- posterior cranial fossa: cerebellum, medulla, pons
Middle Cranial Fossa Contents
- temporal lobe of brain
- pituitary gland
- internal carotid artery, opthalmic arteries
- middle meningeal vessels and nerves
- cavernous sinus
- cranial nerves: CN II, III, IV, V, VI
- trigeminal ganglion (CN V)
- autonomic nerves: greater (CN VII) and lesser (CN IX) petrosal nn.
Cavernous Sinus Contents (nerves/arteries)
- Internal carotid artery
- CN III- oculomotor n.
- CN IV- trochlear n.
- CN V1- opthalmic n.
- CN V2- maxillary n.
- CN VI- abudcent n.
Anastomosis
- an alternative route for vascular flow
- multiple pathways of getting blood to or from the source
- seen around joints, organs with high vascular requirements
Carotid arteries
- external carotid a.
- supplies face, scalp, skull, meninges
- internal carotid a.
- supplies brain, eyes
- carotid sinus and body at bifurcation of carotid aa.
- monitor blood chemistry and pressure
venous drainage of superficial face
- facial vein
- common facial vein
- internal jugular vein
- brachiocephalic vein
- superior vena cava
Opthalmic veins
- connect cavernous sinus to facial veins
Cavernous sinus
- intracranial
- found in middle cranial fossa
- surrounds the internal carotid artery
Cavernous sinus drainage
- Cavernous sinus
- Sigmoid sinus
- Internal jugular vein
- right brachiocephalic vein
Anterograde flow
at rest, blood drains inferiorly from the facial v. to the internal jugular v.
retrograde flow
- intracranial hyperthermia (the brain gets hot!), blood drains posteriorly through the orbits (opthalmic vv.) to the cavernous sinus
- counter-surrent cooling
- venous blood in the cavernous sinus cools arterial blood in the internal carotid artery before brain
danger triangle
retrograde venous flow from skin in this region can spread skin infections into the cavernous sinus, meninges, and brain
Cranial nerves
I: Olfactory
II: Optic
III: Oculomotor
IV: Trochlear
V: Trigeminal
VI: Abducens
VII: Facial
VIII: Vestibulochoclear
IX: Glossopharyngeal
X: Vagus
XI: Spinal accessory
XII: Hypoglossal
