Base of the skull : all important viva questions

Viva question of Base of the skull:

1. Define skull:  cranium with mandible is known as skull

Parts of the skull : base of the skull and cranial vault

Ossification : base of the skull : intracartilaginous ossif) & cranial vault : intramembranous ossification

Anatomical points:

1. infraorbital margin and and upper border of external auditory meatus lies in same horizontal line , this line is known as  Frankfort  line

2. orbital cavity directed anteriorly

3. foramen magnum lies horizontally and directed  inferiorly

q. show different view of skull :

norma verticalis : viewed from above

norma frontalis  from front

norma basalis from below

norma occipitalis from behind

norma lateralis from sides

Identification and definition of: bregma, lambda , asterion, pterior  

** pterior: it is the meeting point of 4 bones frontal , squamous part of temporal bone, parietal bone and greater wings of sphenoid clinical important : deep to this point branches of middle meningeal vessels are present . this vessel torn in accident , barr hole operation done here

Cranial fossa : three in number anterior, middle and posterior

Learn Boundary and content of each cranial fossa :

 *** foramen through which cranial nerves are passage 

 

Identify the sulcus which lodges cranial dural sinus

Cranial dural sinus

Cranial dura has two layer : endoesteum layer and meningeal layer

The sinuses of the dura mater are venous channels which drain the blood from the brain;

They are situated between the two layers of the dura mater

They are devoid of valves, and and lined by endothelium but no smooth muscle cells layer.

Different types of dural venous sinus:

1. Pair: cavernous sinus, transverse sinus, sigmoid sinus etc.
2. unpair: superior sagittal sinus, inferior sagittal sinus, straight sinus etc.

Superior sagittal sinus > right transverse sinus > right sigmoid sinus > right internal jugular vein

 Inferior sagittal sinus > straight sinus > left transverse sinus > left  sigmoid sinus > left internal jugular vein

 The cavernous sinuses are placed one on either side of the body of the sphenoid bone, extending from the superior orbital fissure to the apex of the petrous portion of the temporal bone.

 Medial wall (central part) is related to –

1. the internal carotid artery,
2. abducent nerve.

Lateral wall : is related to

1. the oculomotor
2. trochlear nerves,
3. the ophthalmic nerves
4. maxillary divisions of the trigeminal nerve  

The cavernous sinus : tributaries :

1. the superior ophthalmic vein
2. superior and inferior  petrosal sinus
3. pterygoid venous plexus veins
4. The two sinuses also communicate with each other by means of the anterior and posterior intercavernous sinuses.

Sulcus (a bony impression)	Structure lodge on sulcus	Bone
Sagittal sulcus	Superior sagittal sinus	Frontal bone, parietal bone, occipital bone
Transverse sulcus	Transverse sinus	occipital bone
Sigmoid sulcus	Sigmoid sinus	Mastoid part of temporal bones

 

q. Identify the Suture :  coranal , sagittal, lamdoid suture

q:  Suture,  what type of joint: fibrous variety

Location of anterior and  posterior frontanelle and their time of closer

Anterior frontanelle : located in between coronal and sagittal suture close : 8–24 months after birth

Pos frontanelle : located in between coronal and lambdoid suture. close : 6–8 weeks after birth