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recitation: headneckII

What forms the primary prominence? an unpaired frontonasal prominence, paired maxillary processes & paired mandibular processes.
What innervates the frontonasal prominence? What does it become? V1. Turns into forehead.
What innervates the maxillary processes? What do those become? V2. Turns into upper jaw.
What innervates the mandibular processes? What do these become? V3. Turns into lower jaw, the "primordial floor of the mouth".
What do the maxillary processes and mandibular processes develop from? 1st branchial arch.
What happens if the mandibular processes don't fuse midline? You get a cleft mandible and/or cleft lower lip
What is the epithelium of the oral cavity derived from? Ectoderm, b/c it covered the branchial arch that formed the mandibular processes.
What does the frontonasal prominence become? The forehead/bridge of nose.
What forms the nasal cavities? The nasal placodes that invaginate to form nasal pits/sacs.
What forms the primitive choana? When the dorsal section of the oronasal membrane breaks down.
What does the oronasal membrane do? It separates the oral cavity from the inferior dorsal part of the nasal pit.
What do the median nasal processes fuse with? What is formed? With ea other! They form the intermaxillary segment.
What gets pushed ventrally out of the way when the median nasal processes fuse? The frontaonasal prominence.
What does the rostral portion of the intermaxillary segment become? What about the caudal portion? Rostrally, it become the philtrum. Caudally, it becomes the primary palate.
What do the lateral nasal processes fuse with? The maxillary process.
What separates the lateral nasal processes from the maxillary process? The nasolacrimal groove.
What forms the nasolacrimal duct? When the lateral nasal processes fuse with the maxillary process, but leave behind a cord of epithelial cells that make the canal that will be your duct.
What happens if the lateral nasal processes don't fuse with the maxillary processes? You get an oblique facial cleft that goes all the way up to the medial canthus.
What fuses to the philtrum to finish making the upper lip? What happens if the fusion doesn't happen? The fusion of intermaxillary segment with the maxillary processes. If fusion fails, you get cleft lip.
What forms the secondary palate? When the lateral palatine processes grow caudally from maxillary process and fuse to each other...
What has to happen before the secondary palate can form? The tongue has to move out of the way, and THEN the lateral palatine processes rotate to horizontal orientation to fuse.
How do the hard and soft palate form? When the primary palate (ventral) meets up with the secondary palate (dorsal).
What happens if the primary and secondary palate never meet up? You get a cleft palate.
What does the tongue develop from? The midline of the 5 branchial arches, where there are prominences that develop from top to bottom.
What are the prominences that form the tongue from first to last? Tuberculum impar, copula, hypobranchial eminence & epiglottic eminence.
Where does tuberculum impar come from? What does it form? 1st arch. The ROSTRAL 2/3 of tongue.
Where does copula come from? 2nd arch
Where does hypobranchial eminence come from? What does it form? Mostly 3rd and some 4th arch. The caudal 1/3 of the tongue, and the 4th arch region (more caudal) gives rise to epiglottic eminence.
Where does epiglottic eminence come from? What does it form? 4th arch. Epiglottis.
What does the lateral lingual eminence do? What is it a part of? It overgrows the tuberculum impar, and is also part of 1st arch.
What does the hypobranchial eminence do? Obliterates copula.
What does the foramen cecum and sulcus terminals act as a demarcating boundary for? Rostral 2/3 of tongue and caudal 1/3 of the tongue.
What innervates 3rd arch? And What part of the tongue does it form again? CN9, and will innervate posterior 1/3 of tongue, specifically with lingual branches.
What innervates 4th arch? What comes from 4th arch again? CN10 (VAGUS) innervates epiglottis from 4th arch!
What innervate the vallate papillae? CN9...NOT CN7, which is what you'd like to think with chorda tympani and taste. This is the EXCEPTION for the taste buds/taste in gen.
Where do the extrinsic and intrinsic tongue muscles come from? What innervate the intrinsic tongue muscles? Occipital somites that turn into myoblasts and move to tongue area. They're innervated by CN7.
Where does the thyroid develop? Between the tuberculum impar (1st arch) and copula (2nd arch).
How did the thyroid migrate to its present location? Thyroid cells invaginated in btwn the 1st and 2nd arch and moved caudally thru floor of pharynx leaving behind the thyroglossal duct. Eventually, duct gets cut and it moves further down to final resting spot.
What does the thyroglossal duct become? Foramen cecum
What if the thyroglossal duct regresses? It becomes a thyroglossal duct cyst.
What if the thyroglossal duct never closed off? It becomes a thyroglossal duct sinus.
Where do the parafollicular cells of the thyroid come from? How do they help form the thyroid? Neural crest cells from the ultimobranchial/postbranchial bodies. They move down to 4th arch & ventrally to collide with thyroid follicular cells/primordial thyroid that were moving down and get mixed in there, forming the thyroid.
What forms the inner ear? The otic placode
How does the inner ear form? Otic placode invaginates to form otic pit. Pit is pinched off to make otic vesicle. SHh & WNts/BMPs help differentiate vesicle into pts of the inner ear & the epithelium helps form otic capsule for cartilage.
Which direction does SHh work in? What direction does WNts/BMP work? SHh goes ventrally. WNts/BMPs go dorsally.
What does the first outgrowth of the otic vesicle become? Endolymphatic duct.
What does the dorsal part of the otic vesicle give rise to? The utricle and semicircular canals (look like pancakes at first, then donuts).
What does the ventral part of the otic vesicle form? Saccule & cochlea
What does the otic vesicle epithelium do? Induce mesenchyme around it to condense & turn into cartilage, which makes the otic capsule.
What does the otic capsule become? The petrous part of the temporal bone that gives way to perilymphatic space.
What does the otic placode give rise to specifically (don't just say "inner ear!") Otic vesicle & sensory neurons in vestibular and cochlear ganglia.
What was our eye field(s) like at first? Eye line starts as ONE transverse groove that crosses along midline.
What directs the splitting of the central pt of transverse groove? SHh inhibitory signals of central portion of transverse growth will cause growth only laterally & bilaterally.
What happens if there is a dysfunction in SHh signaling? Then you get holoprosencephaly (eyes are close together) and dyclopia (one eye, b/c the field didn't split well.)
What is the optic vesicle connected to? Neural tube via optic stalk. So lumen of vesicle, tube & stalk are all continuous.
How does the lens form from the optic vesicle? Vesicle moves mesenchyme out of the way and reaches placodal ectoderm. This weakens the inhibitory signals from the mesenchyme on the ectoderm. Now ectoderm can form the lens placode that makes the lens...eventually.
How do you get the lens from the lens placode? Lens placode will invaginate to form lens pit & pinches off to form lens vesicle. And...that will eventually become lens.
How does the lens vesicle become the lens? It is filled with fluid at first, but then it gets signals from optic cup posteriorly that causes the epithelial cells to get longer and form lens fibers, getting rid of the fluid and becoming a real lens.
What is the optic cup? When the lens vesicle pushed back into the optic vesicle, causing the optic vesicle to invaginate & cup in. This makes it bi-layered. *fist in balloon analogy*
What is the retina made up of? Pigmented epithelium, intraretinal space, and neural retina.
What is the pigmented epithelium? The outer layer of the optic cup that is still continuous with optic stalk. But it doesn't do anything sensory.
What is the intraretinal space? It is what is left of the optic vesicle lumen remnant & is still continuous with optic stalk lumen.
What happens when the retinal layers fuse? What happens if they don't fuse fully? The intraretinal space disappears. If they don't fuse, then you can get retinal detachment.
What is the neural retina? It is the part of the retina that gives rise to sensory neurons (rods & cones) and interneurons (horizontal & amacrine cells), that all come together back to optic stalk to make optic nerve.
What is the choroidal fissure? A ventral "crack" in the optic cup that contains the hyaloid artery running through it.
What does the hyaloid artery supply? What does it become? It supplies neural retina, vitreous body & lens. The distal part will regress & the proximal part that is left will be the central artery of the retina.
What forms the vitreous body? When fibroblasts fill up the space behind the optic cup where it invaginates (b/c of the lens) with Type II collagen~
What forms the choroid & sclera? The optic cup & stalk inducing the mesenchyme around it to turn into choroid & sclera.
What is the choroid continuous with & what does it do? It's continuous with pia & arachnoid. Provides blood supply to outer layers of eye.
What is the sclera continuous with & what does it do? Is external to choroid & continuous with dura matter. It is the sheath to optic nerve.
What does the cornea come off of? The cutaneous ectoderm that was outside of the lens vesicles after it's been pinched off to make primary stroma...that will eventually become cornea.
How does the cornea form? When secondary stroma forms from the ECM and hyaluronic acid from corneal endothelium. Hyaluronidase comes in later to reduce water content & make the cornea thin.
What is Descemets membrane? An acellular matrix that forms between secondary stroma & corneal endothelium.
What is corneal endothelium from? Mesenchyme from under the primary stroma.
How do the anterior chambers form? Fluid filled spaces in mesenchyme deep to cornea expand & comes together to make one big space.
What separates the anterior chamber from the lens? A pupillary membrane.
How does the pupil form? When pupillary membrane starts to degrade from the center. This allows communication between & creates a posterior chamber.
How does the posterior chamber form? After the pupillary membrane breaks down in the center & the eye epithelium at the anterior end has become continuous with the pigmented epithelium.
Created by: h.pang00