Block 4: TBL 7 Learning Objectives

Question 1

What are the boundaries of the anterior cranial fossa?

Answer 1

frontal bone
limbus of sphenoid bone
lesser wings of sphenoid bone

Question 2

What are the boundaries of the middle cranial fossa?

Answer 2

dorsum sellae of sphenoid bone and clivus, petrous part of temporal bone, squamous part of occipital bone

Question 3

What are the boundaries of the posterior cranial fossa

Answer 3

dorsum sellae of sphenoid bone, petrous part of temporal bone, squamous part of occipital bone, petromastoid part of the temporal bone

Question 4

Bones of the anterior cranial fossa

Answer 4

frontal bone, ethmoid bone, sphenoid bone

Question 5

What does the anterior cranial fossa accommodate?

Answer 5

inferior portions of the frontal lobes of the brain

Question 6

Bones of the middle cranial fossa

Answer 6

sphenoid and 2 temporal bones

Question 7

What does the middle cranial fossa accommodate?

Answer 7

pituitary gland & 2 lateral parts accommodate the temporal lobes of the brain

Question 8

Bones of the posterior cranial fossa

Answer 8

mainly temporal and occipital bones w/ small contributions from parietal and sphenoid bones

Question 9

What does the posterior cranial fossa accomodate?

Answer 9

cerebellum and brainstem

Question 10

Describe the organization and function of the meninges

Answer 10

the meninges are organized into 3 layers:

dura mater: tough outer layer with 2 connective tissue sheaths
arachnoid mater: delicate, inner layer that lines (but is not adherent to) the dura mater
pia mater: inner layer firmly attached to the surface of the brain, entering the grooves and fissures on the surface

Question 11

Describe the divisions of the dura mater

Answer 11

periosteal layer: lines the inner surface of the cranial bones, contains the meningeal arteries
meningeal layer: deep to the periosteal layer; in close contact w/ arachnoid mater

Question 12

Describe the structure and function of the dural reflection and list the types

Answer 12

s(x): areas where the meningeal layer of the dura mater folds inwards
f(x): partition the brain and divide the cranial cavity into several parts
types: falx cerebri & tantorium cerebelli

Question 13

Falx Cerebri

Answer 13

downward projection of dura mater lining the skull that passes b/w the 2 cerebral hemispheres

Question 14

Tentorium Cerebelli

Answer 14

horizontal projection of the meningeal dura mater that covers and separates the cerebellum in the posterior cranial fossa from the posterior parts of the cerebral hemispheres

Question 15

What is the arterial supply to the dura mater?

Answer 15

the dura mater is highly vascularized & is supplied by the anterior meningeal arteries, middle & accessory meningeal arteries, and posterior meningeal arteries

Question 16

Describe the arachnoid mater

Answer 16

avascular and unninervated meningeal layer that lines the inner surface of the dura mater

Question 17

Subarachnoid Space

Answer 17

space beneath the arachnoid mater that contains CSF to cushion the brain

Question 18

Arachnoid Granulations

Answer 18

small projections of the arachnoid mater into the dura mater that allow CSF to re-enter circulation via the dural venous sinuses

Question 19

Which meningeal layers are vascularized?

Answer 19

dura mater

pia mater

Question 20

What is the function of the meningeal layers?

Answer 20

provide supportive framework for cerebral & cranial vasculature

in combination w/ CSF, protects the CNS from mechanical damage

Question 21

Describe the blood supply to the brain

Answer 21

the brain receives arterial supply from 2 pairs of vessels: vertebral and internal carotid arteries, which are connected in the cranial cavity to form an anastamotic circle (cerebral arterial circle of willis)

Question 22

What forms the cerebral arterial circle of willis?

Answer 22

formed by an anterior communicating artery connecting the L and R anterior cerebral arteries to eachother & 2 posterior communicating arteries connecting the internal carotid artery w/ the posterior cerebral artery

Question 23

Describe the origin and course of the internal carotid arteries

Answer 23

origin: from the bifurcation of the common carotids @C4
course: move superiorly within the carotid sheath to reach the base of the skull. they enter the cranial cavity and pass through the cavernous sinus

the brain via the carotid canal.

Question 24

What are the branches of the internal carotid artery?

Answer 24

ophthalmic artery
posterior communicating artery
middle cerebral artery
anterior cerebral artery

Question 25

Describe the course of the vertebral arteries

Answer 25

arise from the subclavian arteries and ascend to the posterior aspect of the neck through the foramen transversum enter the cranial cavity via the foramen magnum

Question 26

Describe the organization of the major dural venous sinuses that drain blood from the brain

Answer 26

the dural venous sinuses lie between the periosteal and meningeal layer of the of the dura mater. They drain blood from the CNS, face, and scalp. All dural venous sinuses ultimately drain into the internal jugular vein, and these sinuses do not have valves. There are 11 sinuses in total.

Question 27

List the locations of various dural sinuses

Answer 27

the straight, superior, and inferior sagittal sinuses are found in the falx cerebri of the dura mater and these sinsues converge at the confluence of sinuses the straight sinus is a continuation of the great cerebral vein and the inferior sagittal sinus

Question 28

Confluence of Sinuses

Answer 28

a dilated space at the internal occipital protuberance that is drained by the right and left transverse sinus

Question 29

Name each cranial nerve and the openings through which each nerve communicates with the cranial cavity

Answer 29

``` Cribiform plate: olfactory nerve (CNI) optic canal: optic nerve (CNII) superior orbital fissure: oculomotor nerve (CNIII) trochlear nerve (CNIV) ophthalmic nerve (CNV1) abducens (CNV) ``` foramen rotundum: maxillary nerve (CNV2) foramen ovale: mandibular (CNV3) internal acoustic meatus: Facial N (CNVII), vestibulocochlear nerve (CNVII) ``` jugular foramen glossopharyngeal nerve (CNIX) vagus nerve (CNX) accessory nerve (CNXI) ``` hypoglossal canal: hypoglossal nerve (CNXII)

Question 30

Describe the extra-ocular movements of the eye

Answer 30

elevation: superior pupil movement depression: inferior pupil movement abduction: moving pupil laterally adduction: moving pupil medially internal rotation (intorsion): rotating the upper part of the pupil medially external rotation (extorsion): rotating upper part of the pupil laterally

Question 31

Describe the maxillary artery

Answer 31

it is the largest branch of the external carotid artery in the neck and is a major supply for the nasal cavity, oral cavity, teeth, and dura mater

Question 32

What is the course of the maxillary artery

Answer 32

originates within the parotid gland, passes into the infratemporal fossa, then passes through the pterygomaxillary fissure to enter the pterygopalatine fossa

Question 33

What are the branches of the 1st part of the maxillary artery?

Answer 33

1st part: middle meningeal, inferior alveolar, deep auricular, anterior tympanic, accessory meningeal

Question 34

Describe the middle meningeal artery

Answer 34

the largest of the meningeal vessels and supplies much of the dura mater, bone, and related bone marrow of the cranial cavity walls

Question 35

What are the branches of the 2nd part of the maxillary artery?

Answer 35

deep temporal, masseteric, buccal, pterygoid branches

Question 36

Diplopia

Answer 36

double vision; causes a person to see 2 images of a single object

Question 37

Describe the development of the paranasal sinuses

Answer 37

develop as outgrowths from the nasal cavities and erode into the surrounding bones

Question 38

Describe the characteristics of all the paranasal sinuses

Answer 38

lined by respiratory mucosa open into the nasal cavities innervated by branches of the trigeminal nerve

Question 39

What are the paranasal sinuses

Answer 39

frontal sphenoid ethmoidal maxillary

Question 40

Describe the frontal sinuses

Answer 40

most superior of the sinuses and drain into the nasal cavity via the frontonasal

Question 41

Describe the sphenoid sinuses

Answer 41

drain onto the roof of the nasal cavity; important b/c the pituitary gland can be surgically accessed by passing through the nasal roof, into the sphenoid sinus and through the sphenoid bone

Question 42

Describe the ethmoidal sinuses

Answer 42

3 that all empty into the nasal cavity at different places Anterior: empty into the hiatus semilunaris Middle: empty into the ethmoid bulla Posterior: empty into the superior meatus

Question 43

Describe the maxillary sinuses

Answer 43

largest of the sinuses located inferior to the nasal cavity; drains into the nasal cavity at the hiatus semilunaris, underneath the frontal sinus opening This opening is a potential pathway for the spread of infection; fluid draining from the frontal sinus can enter the maxillary sinus

Question 44

List the venous connections between the dural sinuses and the facial veins and sinuses

Answer 44

Superior ophthalmic vein drains into cavernous sinus Facial vein communicates with with cavernous sinus through that vein Pteryoid venous plexus communicates with cavernous sinus through inferior ophthalmic vein

Question 45

Oculomotor nerve controls

Answer 45

Levator palpebrae superioris | Superior rectus, inferior rectus, medial rectus, inferior oblique

Question 46

Abducens Nerve controls

Answer 46

Lateral rectus muscle

Question 47

Trochlear Nerve controls

Answer 47

Superior Oblique muscle

Question 48

entrapment of the lamina papyrcaea of the ethmoid bone

Answer 48

leads to entrampment of the medial rectus muscle, causing an inability to gaze laterally

Question 49

How does fracture of the anterior cranial fossa present?

Answer 49

CSF rhinorrhea, brusing around the eye