7/22 Part One (Cranial Dvlpmt. & Innerv; Cranial Nerve overview; Cranio-facial muscltr.) Flashcards
Very basically, what are placodes?
neural tissue that will contribute to special senses
The neural plate becomes the DHNT, the neural fold becomes neural crest, but what happens to the part that is lateral to both of those?
it becomes placodes
still neural tissue but NOT neural crest or neural plate
The 3 placodes that we need to “focus” on:
1 = Olfactory (nasal) placode 2 = Optic (lens) placode 3 = Otic (ear) placode
What does the nasal placode start to become…
nerve fibers
Where do the “nerve fibers” of the olfactory placode pass through?
cribiform plate of the ethmoid bone
What does the second placode become? How?
- It becomes the lens of the eye
- It sinks below the surface of the skin and an outgrowth of the brain wraps around it
What does the “outgrowth” that wraps around the lens become?
the retina
The inner ear starts out as what? Then what does it turn into?
Starts out as a lens
Turns into a fluid filled sac
With the otic placode, the fluid filled sac has hairs that are sensitive to what?
movement vibrations (sound) comes into the ear and moves the fluid which moves the hairs and allows you to hear stuff
Movement of the fluid causes movement of the hair and leads to the ability to hear, but what else?
balance
Vestibulocochlear nerve is also called __________ but is usually called the first name because it refers to both balance AND hearing.
auditory nerve
only refers to hearing
The vestibular apparatus and cochlear apparatus are derived from…
the otic placode
What is a somitomere?
smaller portion/division of somites; takes 2 to make one somite
Head (cranial) somites can be divides into how many general regions? What are they?
2
Pre-otic and post-otic
Pre-otic has how many somites?
Post-otic has how many somites?
Pre: 3 somites
Post: the rest (4-5) of the somites
The first 3 somites are associated with the…
developing eye
The post-otic somites represent…
the branchial/pharyngeal/visceral arches
The sclerotomes of the post-otic somites form what?
the floor of the braincase
chondocranium
Since chondrocranium comes from the sclerotome of somites, it is homologous to…
the vertebrae
When the CNS leaves the protection of the vertebral column, what does it now lack?
meninges
What does the myotome of the post-otic somites become?
the muscles of the tongue
What does the myotome of the pre-otic somites become?
the muscles that move the eye