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
Which cranial nerve is associated with the first somite?
CN 3
Which cranial nerve is associated with the second somite?
CN 4
Which cranial nerve is associated with the third somite?
CN 6
The neural crest CANNOT form what?
musculature
Since the muscle can’t come from neural crest, where does it come from?
somites
Once the somite musculature gets dragged down onto the arches and becomes associated with branchial arches, you can no longer call it somatic musculature. You now have to consider it…
branchial musculature
Which nerve is associated with the mandibular arch?
CN 5
Which nerve is associated with the hyoid arch?
CN 7
Which nerve is associated with the 3 arch?
CN 9
Which nerve is associated with the rest of the arches?
CN 10
For the branchial arches, they drag down the myotomes in order to create the branchial musculature. But before that, what did the branchial arches had to have?
What does this mean?
sensory innervation
they have BOTH sensory and motor!
So the types of nerves for each….
Branchial arches:
Placodes:
Somites:
Branchial arches: both
Placodes: sensory
Somites: motor
Nerves.. Number 1: Type: Function: Foramen:
Olfactory
Sensory
Smell
Cribiform plate of ethmoid
Nerves... Number 2: Type: Function: Foramen:
Optic
Sensory
Vision
Optic foramen (optic canal)
Nerves... Number 3: Type: Function: Foramen:
Oculomotor
Motor
Eye movement
Superior orbital fissure
Muscles of the oculomotor nerve:
Superior rectus muscle
Medial rectus muscle
Inferior rectus muscle
Inferior oblique muscle
Not all eye muscles are in the oculomotor nerve. Where are the others?
Superior oblique muscle = Trochlear nerve
Lateral rectus muscle = Abducens nerve
Nerves... Number 4: Type: Function: Foramen:
Trochlear
Motor
Superior oblique
Superior orbital fissure
Cranial nerves that carry parasympathetic innervation out of the skull (covered with meninges then NOT covered any more) are…
CN 3
CN 7
CN 9
CN 10
The actual fibers of cranial nerve 4 come out _________ even though cell bodies are in the ________ aspect.
dorsally
ventral
(they are originally ventral)
Nerve 5:
V1 =
V2 =
V3 =
Trigeminal
V1 = ophthalmic (sensory; SOF)
V2 = maxillary (sensory; rotundum)
V3 = mandibular (both; ovale)
Nerves... Number 6: Type: Function: Foramen:
Abducens
Motor
Lateral rectus
Superior orbital fissure
Nerves... Number 7: Type: Function: Foramen:
Facial Both Facial expression, taste, lacrimal, nasal, salivary glands Enter = internal auditory meatus Exit = stylomastoid foramen
Nerves... Number 12: Type: Function: Foramen:
Hypoglossal
Motor
Tongue
Hypoglossal canal
Details on sensory aspect of V1 (ophthalmic)…
-almost wholly sensory: eyeball, lacrimal gland, conductive, part of nasal mucosa, form brow ridge
V1 carries what kind of parasympathetic fibers? From where to where?
Carries postganglionic parasympathetic fibers from pterygopalatine ganglion (preganglionic from CN 7) to lacrimal gland
V1 also carries sympathetic fibers, but for what?
Where do they synapse?
Where do the postganglionic fibers go?
- dilator papillae from upper thoracic levels
- cranial cervical ganglion
- they reach the ophthalmic nerve via branches of internal carotid artery
Details on sensory aspect of V2 (maxillary)…
-almost whole sensory: lower eyelid down to upper lip, gums and teeth; cheek; nose, palate, & pharynx (partial
What kind of fibers does V2 carry? From where to where?
Carries postganglionic parasympathetic fibers from pterygopalatine ganglion (CN 7) to lacrimal and nasal glands
Details on sensory AND motor aspects of V3 (mandibular)…
- Sensory: lower jaw region, including teeth
- Motor nerve to muscles of mandibular arch: masseter, temporalis, medial & lateral pterygoids, mylohyoid, tensor tympani, anterior digastric, and tensor veli palatini
What kind of innervation is involved with V3? Via what?
Postganglionic parasympathetic innervation to sublingual and submandibular glands via lingual nerve
Any muscle associated with the mandibular arch must receive innervation from where?
V3 (mandibular)
The auriculotemporal branch contains what kind of fibers? It takes them where? Via what?
It contains postganglionic parasympathetic secretomotor fibers that go to the parotid gland via the parotid branches
(preganglionic fibers from CN 9)
