L12 - Skull

Question 1

**describe the bones of the base of the skull?

Answer 1

• underlie the brainstem

- endochondral

Question 2

**bones forming the side and roof of the skull

Answer 2

dermal bones

make up the bones of the face

Question 3

**what forms in the branchial arches

Answer 3

cartilage-replacement elements

Question 4

what is neoteny?

Answer 4

failure to replace cartilage with bone in adults

Question 5

**what are the components of the skull?

Answer 5

chondrocranium (neurocranium and splanchnocranium)

dermatocranium (dermal bone)

Question 6

**what is the chondrocranium and what does it consist of?

Answer 6

the cartilaginous embryonic skull

• the braincase (neurocranium)
• the pharyngeal (gill) arches or splanchnocranium

Question 7

**describe the neurocranium

Answer 7

• makes up most of the mass of cartilage that condenses beneath the embryonic brain and the bones that replace this cartilage
• collectively referred to as basicranium

Question 8

**what are the 3 pairs of cartilaginous capsules? what do they do?

Answer 8

• they house special sensory organs

- olfactory (ant); optic; otic (post)

Question 9

neurocranium: what two pairs of cartilaginous plates forms the floor?

Answer 9

• parachordals (flank the cranial end of the notochord)

- prechordals (hypophyseals) (cranial to notochord and parachordals)

Question 10

neurocranium: what are the bones of the basicranium? what do they represent?

Answer 10

• these represent the primitive vertebrate braincase, therefore all nerves and vessels passing to and from the brain pass through the foraminae in these bones

(5 bones) ethmoid, sphenoid, L/R temporals, occipital