TBL 34

Question 1

What is the floor of the cranial cavity?

The _____-shaped floor is formed by _______.

Answer 1

cranial base is the floor of the cranial cavity

from anterior to posterior, the bowl-shaped floor is formed by three cranial fossae.

Question 2

What forms the anterior cranial fossa (3)?

Answer 2

anterior cranial fossa is formed by the frontal bone
anterolaterally, cribriform plate of the ethmoid bone in the midline, and the lesser wings of the sphenoid bone posteriorly.

Question 3

What forms the posterior edges of the lesser wings? Also (Answer) terminates MEDIALLY as _______.

Answer 3

the sphenoidal crests are the posterior edges of the lesser wings and terminate medially as the anterior clinoid processes.

Question 4

Where are the frontal lobes of the cerebral hemispheres lodged?

Answer 4

the frontal lobes of the cerebral hemispheres are

lodged in the anterior cranial fossa.

Question 5

On the skull, identify the cribriform plate of the ethmoid bone and the frontal bone in the
anterior cranial fossa. Find the lesser wings of the sphenoid bone, the sphenoidal crests,
and the anterior clinoid processes.

Answer 5

Bone (In Lab)

Question 6

the middle cranial fossa is composed of (4)- centrally/laterally.

Answer 6

the middle cranial fossa is composed centrally by
the body of the sphenoid bone and laterally by the greater wings of the sphenoid bone plus the
squamous and petrous parts of the temporal bone.

Question 7

What area of skull accommodates the pituitary gland?

Answer 7

the hypophyseal fossa in the body

of the sphenoid bone accommodates the pituitary gland.

Question 8

Discuss the dorsum sellae.

Answer 8

the dorsum sellae denotes the square posterior wall of the body of the sphenoid bone from which the posterior clinoid processes project superiorly.

Question 9

Where are the superior orbital fissures located and what’s their function?

Answer 9

superior orbital fissures are located beneath the sphenoidal crests and provide conduits between the middle cranial fossa and orbit.

Question 10

the trigeminal ganglion resides in the (structures) and CN V1 traverses the (structure) into the (structure).

Answer 10

the trigeminal ganglion resides in the middle cranial fossa

and CN V1 traverses the superior orbital fissure into the orbit.

Question 11

What’s the origin of the frontal nerve and nasociliary nerve?

Answer 11

CN V1 generates the frontal nerve

the nasociliary nerve is another orbital branch of the ophthalmic nerve.

Question 12

TEMPORAL lobes of the cerebral hemispheres

are lodged in the (structure).

Answer 12

temporal lobes of the cerebral hemispheres

are lodged in the middle cranial fossae.

Question 13

On the skull, locate the superior orbital fissures, body of the sphenoid bone, hypophyseal
fossa and dorsum sellae in the middle cranial fossa.

Answer 13

Bone (In lab)

Question 14

What form the posterior cranial fossa (2)?

Answer 14

the posterior cranial fossa is formed mostly by the

occipital bone and the petrous temporal bone contributes to its anterolateral sides.

Question 15

Identify the jugular foramen and foramen magnum and clivus.

Where is the clivus located?

Answer 15

jugular foramen and locate the foramen magnum and the clivus between the foramen magnum and the dorsum sella.

Question 16

Where does CN XII exit, innervation, serves to transport (fibers)?

Answer 16

CN XII exits the posterior cranial fossa via the hypoglossal canal

it innervates the skeletal muscles of the tongue and transports somatic motor fibers of C1 to the
thyrohyoid and geniohyoid muscles.

Question 17

medulla oblongata and pons of the brainstem
reside (structure).

the midbrain of the brainstem extends from the (structure) into the (structure).

Answer 17

medulla oblongata and pons of the brainstem
reside on the clivus

the midbrain of the brainstem extends from the posterior
cranial fossa into the middle fossa.

Question 18

(2-Structures) reside in the posterior cranial fossa.

Answer 18

occipital lobes of the cerebral hemispheres and the cerebellum reside in the posterior cranial fossa.

Question 19

On the skull, find the squamous and petrous parts of the temporal bone, the occipital bone,
foramen magnum, clivus, hypoglossal canal and jugular foramen in the posterior cranial
fossa.

Answer 19

Bone (In lab)

Question 20

Discuss relation of cranial and spinal meninges.

Answer 20

the brain is covered by cranial meninges that are continuous with the spinal meninges of the spinal cord at the foramen magnum.

Question 21

Discuss how and why the arachnoid is in its relation against the dura?

Discuss the tissue of the pia relation to brain.

Answer 21

the arachnoid is held against the dura by CSF in the subarachnoid space

the pia, several layers of fibroblasts linked by tight junctions and separated by loose connective tissue, adheres to the surface of the brain.

Question 22

Origin of middle meningeal artery and where does it enter (how)?

Answer 22

middle meningeal artery arises from the maxillary artery

in the infratemporal fossa and enters the middle cranial fossa via the foramen spinosum.

Question 23

Discuss what forms the foramen spinosum and grooves.

Answer 23

locate the foramen spinosum and grooves created by the middle meningeal artery and its anterior and posterior branches.

Question 24

veins accompanying the middle meningeal arterial branches traverse the (structure) and empty into the (structure).

Answer 24

veins accompanying the middle meningeal arterial branches traverse the foramen spinosum and empty into the pterygoid venous plexus.

Question 25

What fibers convey somatic sensations from the cranial dura?

Answer 25

CNs V1, V2 and V3 and peripheral fibers from the

DRG at C2 and C3 convey somatic sensations from the cranial dura.

Question 26

dural pain is referred to the (regions) supplied by nerves (provide examples).

Answer 26

dural pain is referred to the cutaneous or mucosal regions supplied by the nerves (e.g., the scalp or skin of the face or neck, or the nasal or oral mucosae).

Question 27

discuss the periosteal layer of the cranial dura and what forms the dural inholdings and dural venous sinuses?

Answer 27

the periosteal layer of the cranial dura adheres
to the inner surface of the cranium and the meningeal layer separates from the periosteal layer to form dural infoldings and dural venous sinuses.

Question 28

superior cerebral veins on the surface of the brain drain into the (structure).

Answer 28

superior cerebral veins on the surface of the brain drain into the superior sagittal sinus.

Question 29

superior sagittal sinus resides in the (structure)

the dural venous sinuses are lined by _____.

Answer 29

superior sagittal sinus resides in the cerebral falx

the dural venous sinuses are lined by endothelium.

Question 30

Describe the cerebral falx and spatial relation function.

Answer 30

cerebral falx is a vertical infolding of the meningeal

dura that partially separates the bilateral cerebral hemispheres.

Question 31

(Portion) of the cerebral falx attaches to the cerebellar tentorium- describe cerebellar tentorium.

its (Portion of the cerebral falx) bony attachment enables the cerebellar tentorium to

Answer 31

posteroinferior portion of the cerebral falx attaches to the cerebellar tentorium, a horizontal dural infolding.

its bony attachment enables the cerebellar tentorium to cover the posterior cranial fossa

Question 32

the tentorium separates (structures)

Answer 32

the tentorium separates the occipital lobes of the cerebral hemispheres from the cerebellum.

Question 33

observe the tentorial notch in the cerebellar tentorium

Answer 33

Informational

Question 34

the midbrain of the brainstem traverses the (structure) as it passes from (structure) into the (structure)

Answer 34

the midbrain of the brainstem traverses the tentorial

notch as it passes from the posterior cranial fossa into the middle cranial fossa.

Question 35

like the superior sagittal sinus, the inferior sagittal sinus
resides in the (structure) and its (fxn) to then form (structure).

Answer 35

like the superior sagittal sinus, the inferior sagittal sinus
resides in the cerebral falx.

it unites with the great cerebral vein, which drains the deep cerebral veins, to form the straight sinus.

Question 36

the confluence of sinuses drains into the (structure) that course along the (spatial relation and structure) to join the (structure) at the (spatial relation and structure).

Answer 36

the confluence of sinuses drains into the right and left
transverse sinuses that course along the posterolateral attached margins of the cerebellar tentorium to join the sigmoid sinuses at the posterior aspect of the petrous temporal bones.

Question 37

the sigmoid sinuses course within (structures) and join the (structures) at the (structure).

Answer 37

the sigmoid sinuses course within deep grooves in

the temporal and occipital bones and join the IJVs at the jugular foramina

Question 38

Describe the cavernous sinuses (lined by and location).

Answer 38

the cavernous sinuses are plexuses of endothelium-lined dural venous channels on the lateral sides of the body of the sphenoid bone.

Question 39

(structures) are the primary tributaries of the cavernous sinuses that drain via the (structure) into the (structures)

Answer 39

the superior ophthalmic veins are the primary tributaries of the cavernous sinuses that drain via the inferior petrosal sinuses into the sigmoid sinuses.

Question 40

the inferior petrosal sinuses also drain into the (structure) that traverses the (structure) to join the (structure).

Discuss the relation to metastasis and distant/near tumors. (provide examples)

Answer 40

the inferior petrosal sinuses also drain into the basilar plexus that traverses the foramen magnum to join the internal vertebral venous plexus of the spinal cord.

metastasis from distant tumors (e.g., prostate or cervical cancer) to the brain occurs via this venous pathway.

Question 41

TINY EMISSARY veins pierce the floor of the middle cranial fossa (fxn).

Answer 41

tiny emissary veins pierce the floor of the middle cranial fossa to allow additional drainage of the cavernous sinuses into the pterygoid venous plexus.

Question 42

On the skull, locate the grooves for the middle meningeal artery, the transverse sinuses,
and the sigmoid sinuses.

Answer 42

Bone (In lab)

Question 43

How can facial infections spread to the cavernous sinus or to the pterygoid venous plexus?

Answer 43

facial vein can travel up to the inferior or superior ophthalmic vein–> cavernous sinus. Deep Facial vein branch from the facial vein—> pterygoid plexus.

Because of these connections, an infection of the face may spread to the cavernous sinus and pterygoid venous plexus.

Question 44

How does thrombophlebitis of the cavernous sinus typically occur?

Answer 44

In persons with thrombophlebitis of the facial vein, pieces of an infected thrombus may extend into the cavernous sinus, producing thrombophlebitis of the cavernous sinus.

Question 45

Why can a fracture of the pterion be life threatening?

Answer 45

Fracture of the pterion can be life threatening because
it overlies the frontal branches of the middle meningeal
vessels, which lie in grooves on the internal aspect of the lateral wall of the calvaria.

A hard blow to the side of the head may fracture the thin bones forming the pterion producing a rupture of the frontal branch of the middle meningeal artery or vein crossing the pterion. The resulting hematoma exerts pressure on the underlying cerebral cortex.

An untreated middle meningeal vessel
hemorrhage may cause death in a few hours.

Question 46

How do the sources and locations of extravasated blood differ with an epidural hematoma, a dural border hematoma, and a subarachnoid hemorrhage?

Note: blood extravasation - the leakage of blood from a vessel into tissues surrounding it; can occur in injuries or burns or allergic reactions. extravasation - the process of exuding or passing out of a vessel into surrounding tissues; said of blood or lymph or urine.

Answer 46

Extradural (epidural) hemorrhage is arterial in origin.
Blood from torn branches of a middle meningeal
artery collects between the external periosteal layer of
the dura and the calvaria. The extravasated blood strips the dura from the cranium.

A dural border hematoma is commonly called a subdural
hematoma; however, this term is a misnomer
because there is no naturally occurring space at the dura– arachnoid junction. Hematomas at this junction are usually caused by extravasated blood that splits open the dural border cell layer. The blood does not collect
within a preexisting space, but rather creates a space at the dura–arachnoid junction . Dural border hemorrhage
is typically venous in origin and commonly results from tearing a superior cerebral vein as it enters the superior sagittal sinus.

Subarachnoid hemorrhage is an extravasation of blood,
usually arterial, into the subarachnoid space.
Most subarachnoid hemorrhages result from rupture of a
saccular aneurysm (sac-like dilation on the side of an artery), such as an aneurysm of the internal carotid artery

Question 47

the forebrain, midbrain, and hindbrain create three (things) and where?

Answer 47

the forebrain, midbrain, and hindbrain create three

dilations in the cephalic end of the neural tube.

Question 48

the forebrain consists of (2) and discuss.

Answer 48

the forebrain consists of the telencephalon that forms the cerebral hemispheres and the diencephalon that forms the optic vesicles, hypothalamus, infundibular stalk, and pars nervosa.

Question 49

the straight sinus runs along the (structure and area) to the (structure) and joins the (structure).

Answer 49

the straight sinus runs along the midline attachment of the cerebral falx to the cerebellar tentorium and joins the confluence of sinuses.

the superior sagittal sinus also empties into the confluence of sinuses.

Question 50

Discuss the draining of the confluence of sinuses.

Answer 50

the confluence of sinuses drains into the right and left
transverse sinuses that course along the posterolateral attached margins of the cerebellar tentorium to join the sigmoid sinuses at the posterior aspect of the petrous temporal bones.

Question 51

Discuss the course of the sigmoid sinuses and (structure) it joins and where.

Answer 51

the sigmoid sinuses course within deep grooves in

the temporal and occipital bones and join the IJVs at the jugular foramina

Question 52

Describe the cavernous sinuses (type of tissue and location).

Answer 52

the cavernous sinuses are plexuses of endothelium-lined dural venous channels on the lateral sides of the body of the sphenoid bone.

Question 53

What are the primary tributaries of the cavernous sinuses and what do (answer) drain into?

Answer 53

the superior ophthalmic veins are the primary tributaries of the cavernous sinuses that drain via the inferior petrosal sinuses into the sigmoid sinuses.

Question 54

Discuss the inferior petrosal sinuses (drain location and join a structure).

Answer 54

the inferior petrosal sinuses also drain into the basilar plexus that traverses the foramen magnum to join the internal vertebral venous plexus of the spinal cord.

Question 55

metastasis from distant tumors (e.g., prostate or cervical cancer) to the brain occurs via _____.

Answer 55

metastasis from distant tumors (e.g., prostate or cervical cancer) to the brain occurs via this venous pathway.

Question 56

a

Answer 56

tiny emissary veins (unlabeled) pierce the floor of the middle cranial fossa to allow
additional drainage of the cavernous sinuses into the pterygoid venous plexus.

Question 57

On the skull, locate the grooves for the middle meningeal artery, the transverse sinuses,
and the sigmoid sinuses.

Answer 57

Bone (In lab)

Question 58

the forebrain, midbrain, and hindbrain create what?

Answer 58

the forebrain, midbrain, and hindbrain create three

dilations in the cephalic end of the neural tube.

Question 59

the forebrain consists of the (structure) that forms the (structures)

the diencephalon forms the (structures).

Answer 59

the forebrain consists of the telencephalon that forms the cerebral hemispheres

the diencephalon forms the optic vesicles, hypothalamus, infundibular stalk, and pars nervosa.

Question 60

the primitive midbrain (aka ______ ) forms the (structure).

the hindbrain consists of the (structures).

Answer 60

the primitive midbrain (aka mesencephalon) forms the midbrain of the brainstem

the hindbrain consists of the metencephalon and myelencephalon.

Question 61

the metencephalon forms the (structures)

the myelencephalon forms the (structure)

Answer 61

the metencephalon forms the pons of the brainstem and the cerebellum

the myelencephalon forms the medulla oblongata of the brainstem.

Question 62

5. From Exencephaly, Anencephaly and Craniorachischisis, pp. 311 and Figure 18.37, pp. 312
   (ME): How do closure defects associated with exencephaly and craniorachischisis differ?
   How can these defects be prevented?

Answer 62

Exencephaly is characterized by the failure of the cephalic part of the neural tube to close. As a result the vault of the skull does not form, leaving the malformed brain exposed. Later this tissue degenerates, leaving a mass of necrotic tissue- anencephaly although brainstem is intact.

In some cases the closure defect of the neural tube extends caudally into the spinal cord and the abnormality is called craniorachischisis. There is anencephaly, but with a large defect involving the spinal cord.

Question 63

the neural tube in the telencephalon forms the (structures).

Answer 63

the neural tube in the telencephalon forms the

lateral (1st and 2nd) ventricles and the 3rd ventricle in the diencephalon.

Question 64

What forms the narrow/wide cerebral aqueduct?

Answer 64

the neural tube in the mesencephalon forms the narrow cerebral aqueduct

Question 65

What forms the 4th ventricle?

Answer 65

the neural tube in the metencephalon and myelencephalon forms the 4th ventricle.

Question 66

the choroid plexus project into (structures and function-rate).

Answer 66

the choroid plexus projecting into the ventricles produces 500 ml CSF/day.

Question 67

Discuss the course of CSF.

Answer 67

CSF flows inferiorly from the lateral ventricles into the 3rd ventricle and via the cerebral aqueduct into the 4th ventricle that directs CSF into the central canal of the spinal cord or into the subarachnoid space of the
cerebral hemispheres, cerebellum, and spinal cord.

Question 68

What creates the subarachnoid cisterns?

Answer 68

enlargements of the subarachnoid space along the inferior surface of the brain create subarachnoid cisterns

Question 69

Discuss the function of the subarachnoid cisterns.

Answer 69

the cisterns prevent compression of the cranial nerve roots and the cerebral arterial circle against the bony cranial base.

Question 70

Define arachnoid granulations.

Answer 70

arachnoid granulations are protrusions of the arachnoid through the meningeal dura mainly in the lumen of the superior sagittal sinus.

Question 71

What covers the arachnoid granulations?

How is CSF volume regulated?

Answer 71

the sinus endothelium covers the arachnoid granulations

CSF volume is regulated by the absorption of CSF across the endothelium into the venous blood of the sinus.

Question 72

Describe and discuss the ependyma (tissue type and location)

Answer 72

ependyma (ciliated, simple cuboidal epithelium) lines the ventricular system of the brain and the central canal of the spinal cord.

Question 73

Discuss glial cells and their proportion in numbers compared to neurons of the CNS.

Answer 73

glial cells (i.e., the ependyma, microglial cells, astrocytes, andvoligodendrocytes) outnumber the neurons of the CNS by 10:1.

Question 74

Discuss the function of oligodendrocytes.

Answer 74

oligodendrocytes support and myelinate the axons of the CNS

Question 75

Define the role of microglial cells.

Answer 75

Microglia, as their name implies, are the smallest glial cell. They act as phagocytes and remove CNS debris, protect the brain from invading microorganisms, and constitute the brain’s immune system.

Question 76

Discuss the formation of the blood-brain barrier.

Answer 76

foot processes of the astrocytes cover most of the capillary endothelial basement membrane, and with tight junctions that link the contiguous endothelial cells, form the blood-brain barrier.

Question 77

Where does obstruction usually occur during obstructive hydrocephalus and why do the calvaria expand?

Overproduction of CSF, obstruction of CSF flow, or
interference with CSF absorption results in excess
fluid in the cerebral ventricles and enlargement of the head, a condition called obstructive hydrocephalus

Answer 77

Although an obstruction can occur any place, the blockage usually occurs in the cerebral aqueduct or an interventricular foramen.

The excess CSF dilates the ventricles, thins the cerebral
cortex, and separates the bones of the calvaria in infants. In infants, the internal pressure results in expansion of the brain and calvaria because the sutures and fontanelles are still open.

Question 78

Why do glial cells form most intracranial tumors, (i.e., gliomas)?

Answer 78

Unlike neurons, glia retain a postnatal ability to divide and are the source of most intracranial tumors, known as gliomas.

Question 79

How do astrocytes respond to CNS injury?

Answer 79

In response to CNS injury, astrocytes undergo

mitosis and are the main source of gliotic scar tissue (gliosis), which may impede neural regeneration.

Question 80

What is the function of the blood-brain barrier?

Answer 80

The BBB restricts passage of large molecules from the capillary lumen to the surrounding tissue, but it allows free passage of gases and selected molecules such as glucose. The barrier protects neurons in the CNS from toxins, drugs, and other potentially harmful substances that may be in the bloodstream.

Question 81

Discuss the origin of the vertebral arteries and the route taken therefore.

Answer 81

the vertebral arteries arise from the subclavian arteries

and ascend in the transverse foramina of the cervical vertebrae.

Question 82

Discuss the route of the vertebral arteries.

Answer 82

vertebral arteries perforate the dura and arachnoid near the foramen magnum to enter the subarachnoid space of
the spinal cord and continue through the foramen magnum into the subarachnoid space of the medulla oblongata.

Question 83

Discuss the formation of the basilar artery. The basilar artery divides into (Structure and location).

Answer 83

the vertebral arteries unite at the inferior border of the
pons to form the basilar artery that divides into left and right posterior cerebral arteries at the superior border of the pons.

Question 84

Return to Figure 7.9 (B), pp. 831 and the skull to identify the carotid canal on the external
surface of the petrous temporal bone. Surmise the internal carotid artery passes through the
canal to enter the middle cranial fossa.

Answer 84

Bone (In lab)

Question 85

Discuss the route out the internal carotid artery towards the ANTERIOR clinoid process.

Answer 85

the internal carotid artery courses anteriorly along the

floor of the middle cranial fossa toward the anterior clinoid process.

Question 86

discuss the route taken by the internal carotid artery in relation to the ANTERIOR clinoid process.

Answer 86

the internal carotid artery makes a 180⁰ turn under the anterior clinoid process and pierces the dura and arachnoid to enter the subarachnoid space (i.e., it becomes the cerebral part of the internal carotid).

Question 87

the cerebral parts of the internal carotid arteries

terminally bifurcates into the (structures).

Answer 87

the cerebral parts of the internal carotid arteries

terminally bifurcates into the anterior and middle cerebral arteries.

Question 88

Discuss the anterior communicating artery and the posterior communicating arteries (what they unite/join).

Answer 88

the anterior communicating artery unites the bilateral anterior cerebral arteries and the posterior communicating arteries join the terminal ends of the internal carotid arteries to the bilateral posterior cerebral arteries.

Question 89

Discuss the function of the the cerebral arterial circle (of Willis).

Answer 89

the cerebral arterial circle (of Willis) on the inferior
surface of the midbrain creates anastomoses between branches of the basilar artery and the left and right internal carotid arteries.

Question 90

Why are the normal anastomoses between the cerebral arteries unable to compensate for arterial obstruction by a
cerebral embolism?

Answer 90

Branches of the three cerebral arteries anastomose
with each other on the surface of the brain.

However, if a cerebral artery is obstructed by a cerebral
embolism (e.g., a blood clot), these microscopic anastomoses are not capable of providing enough blood for the area of cerebral cortex concerned.

Question 91

What is the typical cause of an ischemic stroke and what is its cardinal symptom?

What is a berry aneurysm and where does it commonly occur?

How does hemorrhagic stroke differ from ischemic stroke?

Answer 91

An ischemic stroke denotes the sudden development
of focal neurological defi cits that are usually related to
impaired cerebral blood flow. An ischemic stroke is
generally caused by an embolism in a major cerebral artery. The cardinal feature of a stroke is the sudden
onset of neurological symptoms.

Hemorrhagic stroke follows the rupture of an artery or a
saccular aneurysm, a sac-like dilation on a weak part of the arterial wall.

The most common type of saccular aneurysm is a berry aneurysm, occurring in the vessels of or near the cerebral arterial circle and the medium arteries at the base of the brain.

Question 92

How do the affects of interrupted blood flow to the brain differ after 30 sec, 1-2 minutes, and 5 minutes?

What are the symptoms of TIAs and why does their occurrence increase the risk of other vascular disorders?

Answer 92

An interruption of blood supply for 30 sec alters a person’s brain metabolism.

After 1–2 min, neural function may be lost.

after 5 min, lack of oxygen (anoxia) can result in cerebral infarction.

Transient ischemic attacks (TIAs) refer to neurologic
symptoms resulting from ischemia.

The symptoms of TIA may be ambiguous: staggering, dizziness, light-headedness, fainting, and paresthesias. Persons with TIAs are at increased risk for myocardial infarction and ischemic stroke.