Cranial Cavity

Question 1

What is the cranial floor and what is its function?

Answer 1

Its a flat sheet of bone that supports the brain and special senses/

Question 2

What are the perforations of the cranial floor serve as?

Answer 2

Entrance and exit of nerves and vessels

Question 3

Why did the flat sheet is flexed?

Answer 3

The flat sheet is flexed relative to what is seen in quadrupedal mammals to accommodate for the bipedal posture and that resulted in 3 stepped fossae

Question 4

What is the structure and function of the anterior cranial fossa?

Answer 4

It is found over the orbits and houses the enlarged neocortex and is expanded by the diaghragma sellae. The cribriform plate perforates the floor. The crista galli provides an attachment site for the falx cerebri.
Anterior and posterior ethmoidal arteries, veins and nerves enter/ exit here from orbit on their way to nasal cavity.

Question 5

What expanded the middle cranial fossa?

Answer 5

The tentorium cerebelli

Question 6

What is the function of middle cranial fossa?

Answer 6

• Supports much of the neocortex.
• Serves as entrance/exit site of five cranial nerves and the primary blood supply of the brain (Internal carotid artery)

Question 7

What are the entrances and exits found in the middle fossa?

Answer 7

• Superior orbital fissure; junction between face and brain box; portal for CNs III, IV, V.1, VI, and superior ophthalmic artery
• Optic foramina: portal for CNII
• Foramen Rotundum: portal for V.2
• The foramen ovale: the portal for V.3
• Foramen lacerum:
• foramen spinousom

Question 8

Foramen Lacerum what is it filled with?

Answer 8

• In life it is filled with cartilage, within the cartilage runs the internal carotid artery, which actually runs the cranial cavity in the cavernous sinus.
• this foramen is the cartilaginous/ bony junction of the auditory tube and provides a pathway for the greater superficial petrosal nerves which carry taste and Preganglionic parasympathetic fibers from CN VII.

Question 9

What is the structure and function of posterior fossa?

Answer 9

• Roofed by the tentorium cerbelli, composed primarily of modified vertebrae.
• Houses the brainstem and cerebellum
• Serves as a portal site for 6 cranial nerves as well as the vertebral arteries and jugular vein

Question 10

What are the portals, fossas or canals in the posterior cranial fossa?

Answer 10

• Internal acoustic meatus: CNVII and CNVIII
• Jugular foramen: (IX, X, XI) site where sigmoid and inf. Petrosal sinus split into the internal jugular vein.
• Hypoglossal canal: remnant of intervertebral foramen which CN XII exits from

Question 11

What are the menengies?

Answer 11

the three coverings of the brain, continuous with the spinal cord.

Question 12

Pia Mater

Answer 12

Covers the brain intimately and cannot be separated by gross dissection

Question 13

Arachnoid mater

Answer 13

meaning; spider-like; separated from the pia mater by the subarachnoid space which contains cerebrospinal fluid.

Question 14

Dura Mater

Answer 14

• Outer most layer of menengies
• the subdural space is a large space.
• Composed of a smooth inner layer and a rough outer layer that is fused to the periosteum of the skull.

Question 15

What is a subdural hematoma?

Answer 15

Bleeding into the subdural space that separates the dura mater and arachnoid mater.

Question 16

What runs between endocranium and dura mater and susceptible to damage during head injuries in the temporal region?

Answer 16

The middle meningeal artery. The bleeding of the artery between these layers causes epidural hematoma.

Question 17

What are Dural folds?

Answer 17

Comprise sites where the dura mater separates from the endocranium and invaginates into the cranial cavity as double layered folds that form incomplete partitions.

Check out diagrams (G7.18-7.22)

Question 18

What is a tentorium cerebelli?

Answer 18

• Forms a roof for the posterior cranial fossa
• Partially separates the cerebellum and brainstem from the midbrain.
• The tentorial notch is a gap between tentorium cerebelli through which the brain continues into the middle cranial fossa.

Question 19

What is falx cerebri?

Answer 19

Divides the cerebral hemispheres in the midline.

• joins the tentorium cerebelli posteriorly.
• divides the cerebellum in the midline.

Question 20

What does the diaphragma sellae covers?

Answer 20

The hypophyseal fossa

Question 21

What are the dural venous sinuses?

Answer 21

Constitute the spaces that are lined with endothelium/ they carry venous blood and collect excess cerebrospinal fluid.

Question 22

What 5 sinus occur where the dura mater invaginates to form folds?

Answer 22

• Superior sagittal sinus
• superior petrosal sinus
• trasverse sinus
• confluence sinuses
• occipital sinus

Question 23

Where is the superior sagittal sinus located?

Answer 23

• located in the root of falx cerebri; extends from the crista galli to the confluence of sinuses
• joined by cerebral veins

Question 24

What do arachnoid granulations leak into the venous blood and where do these veins drain into?

Answer 24

-They leak cerebralspinal fluid and the veins then drain into the superior sagittal sinus; that produces pits on the inner surface of the skull roof (Granular fovea)

Question 25

What is the location and extension of superior petrosal sinus?

Answer 25

• Located in the root of the leading edge of the tentorium cerebelli and posterior margin of petrous portion of temporal bone
• extends from the cavernous sinus to the transverse sinus

Question 26

Where is the transverse sinus located and what is its extension?

Answer 26

its located in the root of the tentorium cerebelli from the confluence of sinuses to the junction with the superior petrosal sinus

Question 27

What is the confluence of sinuses and where is it located?

Answer 27

Its the junction of transverse, occipital, straight and superior sagittal sinuses in the midline in the occipital region.

Question 28

Where is the occipital sinus and where does it join?

Answer 28

It’s at the root of falx cerebelli and joins the confluence of sinuses.

Question 29

What 3 sinuses occur where the dura mater simply separates from the endocranium without the association to the dura mater?

Answer 29

-Sigmoid sinus
-Cavernous sinus
-Inferior petrosal sinus
Check out G 7.21-7.26

Question 30

What is the extension of the sigmoid sinus?

Answer 30

Extends from the junction of the transverse and superior sinuses to the jugular foramen

Question 31

Where is the cavernous sinus located, what does it carry and what is ensheathed in its lateral wall?

Answer 31

Located on either side of the sella tucica. It carries a portion of the carotid artery and CN VI. Parts of CN III, IV and V1 are ensheathed in the lateral wall.

Question 32

What does the cavernous sinus communicate with?

Answer 32

Communicates with the ophthalmic veins and pterygoid plexus veins. That could be problematic as pathogens can transmit from the face and mouth to the cranial cavity.

Question 33

what is the extension of the Inferior petrosal sinus?

Answer 33

Extends from the cavernous sinus to the jugular foramen along the inferior margin of the petrous portion of the temporal bone.

Question 34

What 3 sinuses are not associated with the endocranium, but are sinuses between the folds of the dura mater?

Answer 34

• Inferior sagittal sinus
• Straight sinus
• intercavernous (Anterior and posterior) sinus

Question 35

Where is the inferior sagittal sinus located and where does it join?

Answer 35

Located along the inferior margin of falx cerebri and joins the straight sinus

Question 36

what is the Straight sinus continuation of? where does it end and what veins is it joined by?

Answer 36

• Continuation of the inferior sagittal sinus in the junction of the tentorium cerebelli, falx cerebri, and falx cerebelli.
• Joined by the great cerebral veins.

Question 37

Where can you locate the intercavernous sinuses?

Answer 37

Between layers of the dura mater forming diaphragm sellae. Anterior and posterior to the stalk of pituitary; communicates between cavernous sinuses.

Question 38

What are the emissary veins?

Answer 38

Venous channels extending from the dural sinuses to veins outside cranial cavity; they communicate with diploic veins.

Question 39

what are diploic veins?

Answer 39

Run between tables in (diploe) that drain to sinuses or veins of the scalp, head or face.