• Vertebral – two branches off subclavian artery; after entering skull at foramen magnum, they merge to form basilar artery
• Middle meningeal – largest meningeal artery; branch of the maxillary artery; embedded in the external dura; torn when the skull is fractured; enters middle cranial fossa (foramen spinosum) and gives off anterior and posterior branches
• Internal carotid – enters skull through carotid canal in the petrous portion of the temporal bone, enters the cavernous sinus, leaves the sinus giving off the ophthalmic artery, passes inferior to the optic nerve, turns obliquely superiorly (lateral to the optic chiasma) and finally branches into the anterior and middle cerebral arteries
• Posterior inferior cerebellar – off the basilar
• Basilar – formed by union of the vertebrals; joins the internal carotids in the Circle of Willis
• Posterior cerebral – part of the Circle of Willis, supplies the inferior surface and the occipital pole
• Superior cerebral – off the basilar before the Circle of Willis
• Middle cerebral –continuation of internal carotid after it contributes to Circle of Willis; supplies lat. surface and temporal pole
• Anterior cerebral – part of the Circle of Willis; supplies the medial and superior surface of the frontal pole
• Anterior communicating – connects the two anterior cerebrals; part of the Circle of Willis
• Posterior communicating – connects the internal carotid and the posterior cerebral, part of the Circle of Willis

Veins – generally do not follow arteries (unlike in most other parts of the body)

• Superior sagittal sinus – lies in the median plane attached to the border of the flax cerebri
• begins at the crista galla and ends at the internal occipital protuberance in the confluence of sinuses
• Transverse sinuses – pass laterally from the confluence of the sinuses in the attached border of the tentorium cerebelli
• after leaving the tentorium, they become the sigmoid sinuses
• Lacunae lateralis – superior sagittal sinus communicates on each side with these venous spaces in the dura
• Inferior sagittal sinus – smaller than the superior; occupies the posterior 2/3 of the free edge of the falx cerebri
• ends by joining the great cerebral vein (of Galen) to form the straight sinus
• Straight sinus – runs inferioposteriorly along the line of attachment of the flax cerebri to the tentorium cerebelli, where it becomes continuous with one of the transverse sinuses
• Confluens of the sinuses – located behind the lambda in the midline
• Sigmoid sinuses – all of the venous sinuses of the dura eventually deliver most of their blood to the sigmoid sinuses and form them to the internal jugular veins, except for the inferior petrosal sinuses which drain into the IJV directly
• Superior petrosal sinus – small channels that drain cavernous sinuses to the transverse sinuses (Þ sigmoid sinuses)
• Cavernous sinus – large venous sinuses located on each side of the sella turcica and the body of the sphenoid bone
• the internal carotid artery and CN VI are inside each cavernous sinus
• the lateral wall of the sinus contains CN III, CN IV, and CN V₁ and V₂

• Trochlear (CN IV) – quite slender, only CN to cross the midline, innervates the superior oblique muscle of the eye
• Trigeminal (CN V) – large, pierces the pons laterally at the rostral border of the middle cerebellar puduncle
• Facial (CN VII) – just lateral to CN VI, composed of 2 rootlets (proper and intermedius); carries taste from the anterior 2/3 of the tongue, motor info to facial muscles of expression and parasymp. fibers to the salivary and lacrimal glands
• Vestibulocochlear (CN VIII) – hearing and balance; passes through the internal auditory meatus
• Accessory (CN XI) – leaves the skull via the jugular foramen; motor and sensory
• Spinal cord – meets the medulla at the foramen magnum, continues down in the vertebral foramen
• Hypoglossal (CN XII) – motor nerve to the tongue; leaves via the hypoglossal canal in the occipital bone
• Olfactory bulbs and tracts – from the optic chiasma the optic tracts continue dorsolaterally around the midbrain
• Optic (CN II) – passes through the optic canal into the middle cranial fossa to join its partner at the optic chiasm
• Oculomotor (CN III) – moves eye; passes in lateral wall of cavernous sinus and enters orbit through the superior orbital fissure
• Abducens (CN VI) – most medial of the nerves, at jct. of the pons and medulla; innervates the lateral rectus of the eye
• Trigeminal ganglion (CN V) – motor nerve for mastication and the principal general sensory nerve for the head
• Mandibular division (V₃) – nerve to the mandibular prominence (below teeth), purely sensory
• Maxillary division (V₂) – nerve to the maxillary prominence (above teeth, below orbit), purely sensory
• Opthalmic division (V₁) – nerve to the frontonasal prominence (above orbit), sensory and motor
• Greater petrosal – a branch from the facial nerve running through the hiatus of greater petrosal nerve
• Lesser petrosal – leaves the tympanic cavity through the canal for lesser petrosal nerve and passes in the cranium to the sphenopetrosal fissure, or the foramen ovale, or the petrosal foramen through which it reaches the otic ganglion
• Greater occipital (dorsal ramus C2) – medial branch of the dorsal ramus of C2; mainly cutaneous, supplying the back part of the scalp; sends branches to the semispinalis capitis and multifidus cervicis.
• Suboccipital (dorsal ramus C1) – from dorsal ramus of C1; passes through the suboccipital triangle and sends branches to the rectus capitis posterior major and minor, obliquus capitis superiorand inferior, rectus capitis lateralis, and semispinalis capitis

• Temporal – forms side and base of the calvarium; has 4 parts: squamous, petromastoid, tympanic, and styloid process
• Mastoid process – projects anteroinferiorly medial to the ear lobe, superior attachments for sternocleidomastoid
• Pterion – junction of the greater wing of the sphenoid, squamous temporal, frontal, and parietal bones
• Petrous – encloses the internal ear and mastoid cells, forms part of the base of the skull
• Superior petrosal crest
• Occipital
• External occipital protuberance (inion) – the bump at the midline of the superior nuchal line
• Foramen magnum – largest foramen in the skull, lies at the most inferior part of the posterior cranial fossa midway between mastoid processes, where the spinal cord meets the medulla
• Cerebellar fossa – inferior 2 of 4 fossae, for the cerebellar hemispheres (the superior 2 are for occipital poles)
• Jugular foramen – located between the occipital bone and the petrous portion of the temporal bone, transmits the internal jugular vein, CN IX, CN X, CN XI, and the inferior petrosal sinus
• Superior nuchal line – on the external posterior skull, where the trapezius inserts
• Inferior nuchal line – on the external posterior skull, where the rectus capitis posterior major and minor insert
• Ethmoid
• Crista galli – a median process or crest that projects superiorly from the ethmoid bone
• Cribiform plate – forming the side of the crista galli, foramina of these sieve-like plates allow olfactory nerves to enter the anterior cranial fossa
• Sphenoid
• Optic foramen – a.k.a. the optic canal; see "Middle cranial fossa" below
• Atlas (C1 "vertebra") – ring shaped bone that supports the skull
• Posterior arch – the arch on the dorsal side of the "ring"
• Posterior tubercle – the prominence on the midline of the posterior arch
• Transverse process – the processes projecting out laterally from the anterior arch
• Foramen transversarium – the hole that the vertebral artery passes through, in the transverse processes
• Vertebral artery groove – the groove on the posterior arch, posterior to the transverse process, where the vertebral artery travels after exiting the foramen transversarium before it enters the foramen magnum
• Anterior arch – the anterior portion of the "ring"; has it’s own anterior tubercle
• Axis (C2 "vertebra") – looks just like a vertebra, except for the Dens
• Spinous process – often bifid, C2 has a process projecting posterior and inferior in the midline from the lamina
• Vertebral foramen – the hole between the body of C2 and the spinous process, bridged by lamina
• Dens epistrophe (odontoid process) – the portion of C2 that projects superiorly inside the "ring" of C1
• Atlantoaxial joint – the joint between C1 and C2, allows rotation of the head (nodding "no")

• Anterior cranial fossa – shallowest of the three cranial fossae
• Sphenoid – wedge-shaped bone located anterior to the temporal bones, has a body and greater and lesser wings
• Lesser wing of sphenoid – forms the posterior part of the floor of the anterior cranial fossa
• Ethmoid – the crista galli of the ethmoid projects superiorly in the midline of the anterior cranial fossa
• Frontal – the floor of the anterior cranial fossa is made up of the orbital plates of the frontal bone
• Posterior cranial fossa – largest and deepest of the 3 fossae; lodges the pons, medulla, and cerebellum; formed mainly by the anterior and inferior portions of the occipital bone
• Hypoglossal canal – transmits CNB XII; internal opening lies between the jugular foramina and occipital condyle
• Internal acoustic meatus – lies superior to the anterior part of the jugular foramen in the petrous part of the temporal bone; it is closed laterally by a perforated piece of bone that separates if from the inner ear
• Middle cranial fossa
• Superior orbital fissure – an elongated slit between the greater and lesser wings of the sphenoid bone, allows communication between the middle cranial fossa and orbit; traversed by CN III, CN IV, CN V₃, and CN VI
• Foramen rotundum – located in the greater wing of the sphenoid, transmits CN V₂ (the Maxillary nerve)
• Foramen ovale – in greater wing, transmits CN V₃ (the Mandibular nerve)
• Foramen spinosum – smallest of the 3 in the greater wing, transmits the Middle meningeal artery (largest meningeal artery), the middle meningeal vein, and the meningeal branch of CN V₃
• Hypophyseal fossa (sella) – the sella turcica, houses the pituitary gland
• Optic groove (chiasmatic sulcus)
• Optic canal – allows the optic nerves and opthalmic arteries to enter the middle cranial fossa from the orbits
• Dorsum sellae–rectangular bony projection that forms posterior of sella turcica; separates mid. and posterior cranial fossae
• Foramen lacerum – a ragged foramen located between the body of the sphenoid and the apex of the petrous part of the temporal bone, posteriolateral to the foramen ovale; transmits the internal carotid artery and accompanying sympathetic and venous plexuses
• Carotid groove – a groove in the sphenoid bone for the internal carotid artery

• Frontalis – from the dense subcutaneous tissue above the orbits to the epicranial aponeurosis; wrinkles forehead
• Occipitalis – from the lateral aspect of the superior nuchal line to the epicranial aponeurosis; pulls scalp posteriorly
• both frontalis and occipitalis are innervated by CN VII (facial nerve)
• Semipinalis capitis – arises from the spinous processes of T6-T1 and inserts into the medial ½ of the area between inferior and superior nuchal lines; bilaterally these muscles extend the head; unilaterally they rotate head to opposite side
• Obliquus capitus inferior (inferior oblique) – from the lateral surface of the spinous process of C2 to the inferior surface of the transverse processes of C1; supports the head by pulling on the atlas, but does not insert on the skull
• Rectus capitis posterior major (rectus major) – connects the spinous process of C2 to the inferior nuchal line
• Obliquus capitus superior (superior Oblique) – small triangular muscle that arises from the transverse processes of C1 and inserts into the smaller lateral impression between the superior and inferior nuchal lines; mainly a postural muscle

• Cerebellum – "little brain"; occupies most of the posterior cranial fossa, mainly concerned with motor functions that regulate posture, muscle tone, and muscular coordination
• Cerebral hemispheres – largest part of the brain; comprise the central cortex, basal nuclei, and lateral ventricles
• Frontal pole and lobe – the inferior and anterior extremities of the frontal lobes of the cerebral hemispheres, located in the anterior cranial fossa; anterior to central sulci and superior to lateral sulci
• Temporal pole – the two rounded anterior extremities of the temporal lobes of the cerebral hemispheres
• Occipital pole – contain the visual area, rest of the tentorium cerebelli
• Lateral sulcuc (lateral cerebral fissure) – separates frontal and temporal lobes, as well as parietal and temporal lobes
• Insula – the part of the lateral surface of the hemisphere that is hidden between the frontal and temporal lobes
• Hypophysis cerebi – the pituitary gland, located in the sella turcica

• five layers of the scalp (spell "SCALP": skin, connective tissue, aponeurosis, loose areolar tissue, pericranium)
• (1) Skin – has hair, sweat and sebaceous glands as well as a good vascular supply
• (2) Superficial fascia – thick subcutaneous tissue, richly vascularized and supplied with nerves, fat enclosed in lobules
• (3) Galea aponeurosis – a.k.a. aponeurosis epicranialis or epicranial aponeurosis; connects frontalis and occipitalis forming the epicranius
• (4) Loose areolar tissue – loose connective tissue that allows movement of the scalp
• (5) Pericranium – dense layer of specialized connective tissue, firmly attached to bone via Sharpey’s fibers.
• Posterior atlanto-occipital – ligament connecting posterior arch of C1 to the posterior margin of the foramen magnum
• Meninges – membranes covering the brain
• Dura Mater – thick, tough, external covering; internal layer is continuous with the spinal dura and epineurium of CN’s
• Leptomenix – refers to both arachnoid and pia mater together; Pachymeninx is another term for Dura mater
• Arachnoid – intermediate, thin, cobweblike layer; passes over sulci without dipping into them
• Pia mater – internal, delicate, highly vascular layer; dips into sulci; separated from Arachnoid by CSF
• Arachnoid granulations – hypertrophied aggregations of arachnoid villi (which absorb CSF); often produce erosion or pitting of the internal surface of the superior portions of the frontal and parietal bones
• Flax cerebi – large, sickle shaped, vertical partition in the longitudinal fissure between the two cerebral hemispheres, reduces side-to-side movement
• Diaphragma sellae – small, circular sheet of dura that forms a roof over the sella turcica

• Subdural hematoma – bleeding within the dura
• Cisterna cerebellomedullaris (cisterna magna) – space between cerebellum and inferior part of the medulla; receives CSF from median aperture of the 4^th ventricle and is continuous with the subarachnoid space around brain and spinal cord
• Infundibulum – connects the hypothalamus with the pituitary; travels through the diaphragma sellae