Cranial Nerves

Question 1

List all the cranial nerves and the foramine through which they pass.

Answer 1

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

Question 2

. List the three branches of the trigeminal nerve and the foramina through which they pass.

Answer 2

Ophthalmic – Superior Orbital Fissure

Maxillary – Foramen Rotundum

Mandibular – Foramen Ovale

Question 3

Which vessel passes through the optic canal?

Answer 3

Opthalamic artery

Question 4

Which vessel passes through the superior orbital fissure?

Answer 4

Superior Ophthalmic Vein and Inferior Ophthalmic Vein

Question 5

Which foramen does the middle meningeal artery and vein pass through?

Answer 5

Foramen Spinosum

Question 6

Which foramen does the internal carotid artery pass through?

Answer 6

Carotid canal

Question 7

Which vessel passes through the internal acoustic meatus

Answer 7

Labyrinthine Artery

Question 8

Which vessel passes through the jugular foramen?

Answer 8

Sigmoid sinus —- jugular vein

Question 9

Which foramen do the spinal roots of the accessory nerve pass through?

Answer 9

Foramen Magnum

Question 10

Which major arteries pass through the foramen magnum?

Answer 10

vertebral arteries

Question 11

What is the tentorial notch and what is its clinical significance?

Answer 11

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.

Question 12

Describe the facial nerve

Answer 12

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.

Question 13

Describe where the two roots of the facial nerve meet

Answer 13

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.

Question 14

What happens at the geniculate ganglion

Answer 14

At the geniculate ganglion the facial nerve [VII] turns and gives off the greater petrosal nerve, which carries mainly preganglionic parasympathetic (GVE) fibers

Question 15

What else does the facial nerve give off

Answer 15

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).

Question 16

What passes through the petro-tympanic fissure

Answer 16

Chorda tympani

Tympanic arteries and veins

Question 17

What passes through the pterygoid canal

Answer 17

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).

Question 18

What structure is medial to the posterior limb of the internal capsule in a brain cut in the transverse plane?

Answer 18

Thalamus

Question 19

What structure contains the main fibre tracts going up and down from the cortex?

Answer 19

Internal capsule

Question 20

What is the structure that separates the two lateral ventricles

Answer 20

Septum pellucidum

Question 21

Name three structures found within the cavernous sinus

Answer 21

Internal carotid artery

Various cranial nerves (occulomotor, trochlear, trigeminal (ophthalmic and maxillary divisions) and abducens)

Pituitary Gland

Question 22

Which sinus connects the two inferior petrosal sinuses?

Answer 22

Basilar Sinus

Question 23

What is the pterygoid plexus?

Answer 23

A venous plexus of considerable size that is situated between the temporalis muscle and lateral pterygoid muscle, and partly between the two pterygoid muscles

Question 24

Which vein is joined to the end of the straight sinus at the point where the inferior sagittal sinus joins the straight sinus?

Answer 24

Great cerebral vein

Question 25

Which veins drain into the cavernous sinus

Answer 25

Superior and inferior ophthalmic veins

There is also communication with the pterygoid plexus

Question 26

List three different types of brain herniation and their consequences.

Answer 26

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

Question 27

. Describe the arrangement of dural venous sinuses and the direction of blood flow

Answer 27

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

Question 28

What is the name given to the highest point of the protrusion of the occipital bone

Answer 28

inion

Question 29

What are the two horizontal ridges found on the occipital bone

Answer 29

Superior and inferior nuchal lines

Question 30

What part of the mandible that protrudes under the zygomatic bone?

Answer 30

Coronoid process

Question 31

Which bones form the medial part of the orbit

Answer 31

Orbital plate of ethmoid

Frontal process of maxilla

Lesser wing of sphenoid

Lacrima

Question 32

What is the name of the midline notch just below the nose

Answer 32

Anterior nasal spine

Question 33

What is the name of the hole in the mandible through which a branch of the inferior alveolar nerve and vessels pass?

Answer 33

Mental foramen

Question 34

What are the three parts of the ethmoid bone?

Answer 34

Orbital Plate

Middle Nasal Concha

Perpendicular Plate

Question 35

What is another name for the conchae and what is their role?

Answer 35

Turbinate Bones – they increase the surface area of the upper respiratory tract

Question 36

Where does the scalp extend from

Answer 36

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.

Question 37

State the different layers of the scalp

Answer 37

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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

Question 38

Describe the skin of the scalp

Answer 38

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.

Question 39

Describe the dense connective tissue of the scalp

Answer 39

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.

Question 40

Describe the aopneurotic layer of the scalp

Answer 40

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

Question 41

Describe the different parts of the aopneurotic layer

Answer 41

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.

Question 42

Describe the loose connective tissue of the scalp

Answer 42

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

Question 43

Describe the pericranium

Answer 43

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.

Question 44

Describe scalp laceration

Answer 44

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.

Question 45

Summarise arterial supply to the scalp

Answer 45

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.

Question 46

Describe the branches from the opthalamic artery

Answer 46

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.

Question 47

Describe the branches from the external carotid artery

Answer 47

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

Question 48

Describe the venous drainage of the scalp

Answer 48

Follows arteries (and named the same) as branches of external carotid artery supplying the scalep.

Question 49

What accounts for the profuse bleeding following scalp lacerations

Answer 49

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