Cranial Nerves Flashcards
List all the cranial nerves and the foramine through which they pass.
Olfactory (I) – Cribiform Plate
Optic (II) – Optic Canal
Oculomotor (III), Trochlear (IV), Trigeminal (ophthalmic – V1 (V)) and Abducens (VI) – Superior Orbital Fissure
Facial (VII) and Vestibulocochlear (VIII) – Internal Acoustic Meatus
Glossopharyngeal (IX), Vagus (X) and Accessory (XI) – Jugular Foramen
Hypoglossal (XII) – Hypoglossal Canal
. List the three branches of the trigeminal nerve and the foramina through which they pass.
Ophthalmic – Superior Orbital Fissure
Maxillary – Foramen Rotundum
Mandibular – Foramen Ovale
Which vessel passes through the optic canal?
Opthalamic artery
Which vessel passes through the superior orbital fissure?
Superior Ophthalmic Vein and Inferior Ophthalmic Vein
Which foramen does the middle meningeal artery and vein pass through?
Foramen Spinosum
Which foramen does the internal carotid artery pass through?
Carotid canal
Which vessel passes through the internal acoustic meatus
Labyrinthine Artery
Which vessel passes through the jugular foramen?
Sigmoid sinus —- jugular vein
Which foramen do the spinal roots of the accessory nerve pass through?
Foramen Magnum
Which major arteries pass through the foramen magnum?
vertebral arteries
What is the tentorial notch and what is its clinical significance?
Tentorial notch is a triangular opening in the tentorium cerebelli through which the brainstem extends from the posterior to the middle cranial fossa. In the case of increased intracranial pressure, part of the temporal lobe could be pushed through this opening.
Describe the facial nerve
Has SA fibres for taste from anterior 2/3rds of tounge
The facial nerve [VII] attaches to the lateral surface of the brainstem, between the pons and medulla oblongata (Fig. 8.51). It consists of a large motor root and a smaller sensory root (the intermediate nerve):
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The intermediate nerve contains the SA fibers for taste, the parasympathetic GVE fibers, and the GSA fibers.
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The larger motor root contains the BE fibers.
Describe where the two roots of the facial nerve meet
The motor and sensory roots cross the posterior cranial fossa and leave the cranial cavity through the internal acoustic meatus (Fig. 8.50). After entering the facial canal in the petrous part of the temporal bone, the two roots fuse and form the facial nerve [VII]. Near this point the nerve enlarges as the geniculate ganglion, which is similar to a spinal ganglion containing cell bodies for sensory neurons.
What happens at the geniculate ganglion
At the geniculate ganglion the facial nerve [VII] turns and gives off the greater petrosal nerve, which carries mainly preganglionic parasympathetic (GVE) fibers
What else does the facial nerve give off
The facial nerve [VII] continues along the bony canal, giving off the nerve to the stapedius and the chorda tympani, before exiting the skull through the stylomastoid foramen.
The chorda tympani (passes through petro-tympanic fissure) carries taste (SA) fibers from the anterior two-thirds of the tongue and preganglionic parasympathetic (GVE) fibers destined for the submandibular ganglion (salivary glands) (Table 8.6).
What passes through the petro-tympanic fissure
Chorda tympani
Tympanic arteries and veins
What passes through the pterygoid canal
Secretomotor fibers from the parasympathetic part of the autonomic division of the PNS stimulate fluid secretion from the lacrimal gland. These preganglionic parasympathetic neurons leave the CNS in the facial nerve [VII], enter the greater petrosal nerve (a branch of the facial nerve [VII]), and continue with this nerve until it becomes the nerve of the pterygoid canal (Fig. 8.84).
What structure is medial to the posterior limb of the internal capsule in a brain cut in the transverse plane?
Thalamus
What structure contains the main fibre tracts going up and down from the cortex?
Internal capsule
What is the structure that separates the two lateral ventricles
Septum pellucidum
Name three structures found within the cavernous sinus
Internal carotid artery
Various cranial nerves (occulomotor, trochlear, trigeminal (ophthalmic and maxillary divisions) and abducens)
Pituitary Gland
Which sinus connects the two inferior petrosal sinuses?
Basilar Sinus
What is the pterygoid plexus?
A venous plexus of considerable size that is situated between the temporalis muscle and lateral pterygoid muscle, and partly between the two pterygoid muscles
Which vein is joined to the end of the straight sinus at the point where the inferior sagittal sinus joins the straight sinus?
Great cerebral vein
Which veins drain into the cavernous sinus
Superior and inferior ophthalmic veins
There is also communication with the pterygoid plexus
List three different types of brain herniation and their consequences.
Subfalcine – part of the frontal lobe goes under the falx cerebri
Uncal – medial part of the temporal lobe goes under the tentorium cerebelli – which affects the midbrain and can cause unconsciousness
Tonsilar – cerebellar tonsils go through the foramen magnum – this can affect the medulla and cause cardiorespiratory failure
. Describe the arrangement of dural venous sinuses and the direction of blood flow
There is a separation between the dural layers at the top of the falx forming the superior sagittal sinus. There is another separation at the bottom of the falx forming the inferior sagittal sinus. The inferior sagittal sinus drains into the straight sinus, which then joins the superior
sagittal sinus, and the two transverse sinuses at the confluence of sinuses.
The blood drains to the confluence of sinuses and then along the transverse sinuses to the sigmoid sinus, which then forms the internal jugular vein
What is the name given to the highest point of the protrusion of the occipital bone
inion
What are the two horizontal ridges found on the occipital bone
Superior and inferior nuchal lines
What part of the mandible that protrudes under the zygomatic bone?
Coronoid process
Which bones form the medial part of the orbit
Orbital plate of ethmoid
Frontal process of maxilla
Lesser wing of sphenoid
Lacrima
What is the name of the midline notch just below the nose
Anterior nasal spine
What is the name of the hole in the mandible through which a branch of the inferior alveolar nerve and vessels pass?
Mental foramen
What are the three parts of the ethmoid bone?
Orbital Plate
Middle Nasal Concha
Perpendicular Plate
What is another name for the conchae and what is their role?
Turbinate Bones – they increase the surface area of the upper respiratory tract
Where does the scalp extend from
The scalp is the part of the head that extends from the superciliary arches anteriorly to the external occipital protuberance and superior nuchal lines posteriorly. Laterally it continues inferiorly to the zygomatic arch.
State the different layers of the scalp
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S—skin,
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C—connective tissue (dense),
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A—aponeurotic layer,
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L—loose connective tissue, and
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P—pericranium
Describe the skin of the scalp
The skin is the outer layer of the scalp (Figs. 8.67 and 8.68). It is similar structurally to skin throughout the body with the exception that hair is present on a large amount of it.
Describe the dense connective tissue of the scalp
Deep to the skin is dense connective tissue. This layer anchors the skin to the third layer and contains the arteries, veins, and nerves supplying the scalp. When the scalp is cut, the dense connective tissue surrounding the vessels tends to hold cut vessels open. This results in profuse bleeding.
Describe the aopneurotic layer of the scalp
The deepest layer of the first three layers is the aponeurotic layer. Firmly attached to the skin by the dense connective tissue of the second layer, this layer consists of the occipitofrontalis muscle, which has a frontal belly anteriorly, an occipital belly posteriorly, and an aponeurotic tendon— the epicranial aponeurosis (galea aponeurotica)—connecting the two
Describe the different parts of the aopneurotic layer
The frontal belly of the occipitofrontalis begins anteriorly where it is attached to the skin of the eyebrows. It passes upward, across the forehead, to become continuous with the aponeurotic tendon.
Posteriorly, each occipital belly of the occipitofrontalis arises from the lateral part of the superior nuchal line of the occipital bone and the mastoid process of the temporal bone. It also passes superiorly to attach to the aponeurotic tendon.
The occipitofrontalis muscles move the scalp, wrinkle the forehead, and raise the eyebrows. The frontal belly is innervated by temporal branches of the facial nerve [VII] and the posterior belly by the posterior auricular branch.
Describe the loose connective tissue of the scalp
A layer of loose connective tissue separates the aponeurotic layer from the pericranium and facilitates movement of the scalp proper over the calvaria (Figs. 8.67 and 8.69). Because of its consistency, infections tend to localize and spread through the loose connective tissue
Describe the pericranium
The pericranium is the deepest layer of the scalp and is the periosteum on the outer surface of the calvaria. It is attached to the bones of the calvaria but is removable, except in the area of the sutures.
Describe scalp laceration
The scalp has an extremely rich blood supply from the external carotid arteries, so lacerations of the scalp tend to bleed profusely. Importantly, scalp bleeding is predominantly arterial, because of two reasons. First, in the erect position the venous pressure is extremely low. Second, the vessels do not retract and close when lacerated because the connective tissue in which they are found holds them open.
Summarise arterial supply to the scalp
Arteries supplying the scalp (Fig. 8.71) are branches of either the external carotid artery or the ophthalmic artery, which is a branch of the internal carotid artery.
Describe the branches from the opthalamic artery
The supratrochlear and supra-orbital arteries supply the anterior and superior aspects of the scalp. They branch from the ophthalmic artery while it is in the orbit, continue through the orbit, and exit onto the forehead in association with the supratrochlear and supra-orbital nerves. Like the nerves, the arteries ascend across the forehead to supply the scalp as far posteriorly as the vertex of the head.
Describe the branches from the external carotid artery
Three branches of the external carotid artery supply the largest part of the scalp—the superficial temporal, posterior auricular, and occipital arteries supply the lateral and posterior aspects of the scalp
Describe the venous drainage of the scalp
Follows arteries (and named the same) as branches of external carotid artery supplying the scalep.
What accounts for the profuse bleeding following scalp lacerations
Neurovascular structures are contained in the dense connective tissue layer and the dense nature of this layer is responsible for the profuse hemorrhaging accompanying scalp lacerations. This is because the dense connective layer does not retract; therefore, blood vessels are held in an open position.
Needs to be sutured urgently
