Treacher-Collins Syndrome

• first arch syndrome
• small mandibles and zygomatic bones(formed by mandibular prominence)
• malformed external ears(partly formed by first arch)
• down slanted palpebral fissures(eye openings), incompletely formed lower eyelids (formed by maxillary prominence)
• deafness resulting from malformed ossicles(meckels cartilage) and middle ear cavity(formed by first pouch

Aperts Syndrome

• rare, autosomally dominant congenital syndrome
• nearly always caused by a mutation in the parent in the gene for the receptor of signaling protein FGF2
• underdeveloped mid-face
• loss of hearing
• syntosis of calvarium, but enlarged fontanelle
• polydactyly and syndactyly
• doesnt run in familys

Developmental Anomalis of 

Face and Palate

• 1:1000 births
• orginate during weeks 6-9 of development
• can be surgically corrected, but their developmental background has to be understood
• median cleft of lower and upper lip, complete unilateral cleft of upper lip and primary palate, bilateral oblique facial cleft, macrostomia, complete unilateral cleft of upper lip

Median Cleft of the Lower Lip

• failure of the left and right mandibular prominences to fuse(below lip)

Median Cleft of the Upper Lip

• failure of the left and right medial nasal prominences to fuse

Complete Unilateral Cleft of the Upper Lip

and unilateral cleft of primary palate

• failure of maxillary and medial nasal prominences to fuse

Bilateral Oblique Facial Cleft with 

Complete Bilateral Cleft lip and

exposed nasolacrimal duct

• failure of maxillary prominences to fuse to medial and lateral nasal prominences

Macrostomia(Bilateral Facial Cleft)

• failure of maxillary and mandibular proceses to fuse
• macrostomia means big mouth opening(joker)

Cleft of Maxilary prominences and 

Palantine Shelves?

• failure of left and right palantine shelves to fuse

Pharangeal Arches

• pharyngeal arches at end of gut tube are segmented area by stomodeum
• have a skeleton that consist of cartilage bars

Development of Face

• Frontonasal prominence (swelling): bulging of forehead of embryo, underlain by bulging brain
• nasal placode: thickening of epithelium that will form dimple in embryos face and is induced by underlying brain
• placodes form ears, eyes and nose
• First pharyngeal arch: splits into maxillary and mandibular prominence that surrounded the stomodeum

Philtrum

• flat area between upper lip and nose formed by medial nasal prominence

Development of Palate Pt 1

• nasal cavity develops as invagination of nasal pit
• oral cavity develops from foregut
• nasal and oral seperated by oronasal membrane that disapears
• palate then forms to separate all but a little part 

Coloboma Iridis

• normally choroid(neuroectoderm) or optic cup surrounds the entire perimiter of lens
• when it doesnt a cleft is left in the iris connecting pupil to sclera
• persistance of choroid fisure 
• can be small or large and symptoms range from none to blindness 

Layers of Optic Cup

• external layer forms the pigmented layer of the retina
• internal layer froms all other(neural) layers of the retina
• also forms other structures, including parts of the iris, optic nerve and ciliary body

German Measles in

Pregnant Women

• If contracted before and around week 7 then congenital cataracts is developed in child 
• if they occur later then hearing damage is more likely since the ear develops later then the eye

Sclera and Choroid Formation

• formed by mesenchyme cells that surround the optic cup 
• cells also form vitreous body, dilator and constrictor papillae and part of iris and part of the cornea

Iridopupillary membrane

• sheet of mesenchyme posterior to the anterior chamber
• disappears and the resulting foramen is the pupil
• persistance of the membrane results in strands of connective tissue suspended anterior to the lens

Development of Bony Labyrinth

(cochlea)

• mesenchyme surround membranous becomes cartilage (otic capsule)
• two long narrow spaces around membranous labyrinth of the cochlea are formed from vacuolization forming scala vestibuli and tympani 
• organ of corti, basilar membrane reissners membrane all form from otic visicle(ectoderm origin)

Auricle Development

• develops from edge of pharyngeal arch I and II (pharyngeal cleft 1)
• congenital deformations usually do not interfere with function but can alert physicians to high likelihood of presence of malformations not apparently external
• innervation of external ear very complex

Optic Vessicle Development

• forms as a bulge from brain(grows laterally)
• thin overlying area is lens placode(epithelium)
• optic vesicle invaginatesm making double walled optic cup that goes around it
• lens placode buds off forming the lens vessicle that forms lens

Optic Cup

• surrounds lens becoming choroid and remaining opening is the pupil
• choroid fissure is area around lens that is not fused in development but normally fuses all the way in adults
• imagine one circle surrounding the another circle

Otic Vessicle Formation

• otic placode fors in neck, lateral to posterior brain
• otic placode invaginates, forming otic pit
• otic pit releases from surface and forms otic vessicle

Otic Vessicle Transformation

(formation of membranous labyrinth)

• grows and divides into sacule, utricle and endolymphatic duct
• cochlear duct develops by curving growth of the thin bottom part of sarcule
• semicircular canal develops by flattening of 3 parts of utricle, eventually walls touch and disapear, leading to 3 circular canals

Pharyngeal Arch Contents 

• ectodermal epithelium
• endodermal epithelium
• cartilaginous skeleton
• segmental artery 
• cranial nerve

Meckel's Cartilage

• cartilaginous support of first Arch
• located in mandibular prominence
• most of it dissapears in development except the posterior part remains and osifies to form the malleus and incus(neural crest ectoderm)

Intramembranous Bone of First Arch

• maxilla, zygomatic bone and even part of the squamous part of temporal bone

Mandibular Arch

• CN V.3
• masseter, temporalis, pterygoids, mylohyoid, digastric, tensor tympani
• meckels cartilage, malleus, incus, sphenomandibular lig, maxilla and mandible

Hyoid Arch

• CN VII
• facial expr, stapedius, stylohyoid, digastric
• stapes, styloid process, stylohyoid lig, hyoid (all cartilage preformed)

Pharyngeal Arch III

• CN IX(glossopharyngeal)
• stylopharngeus muscle
• hyoid(greater hom, inf body)

Pharyngeal Arches IV/VI

• IV is super laryngeal of CN X
• VI is recurent laryngeal of CN X
• cricothyroid, levator palatini, pharyng constrictors (IV)
• intrinsic laryngeal mm (VI)
• laryngeal cartilages

Branchial Cleft 1 and

Pouch 1

• external auditory meatus (cleft)
• tubotympanic recess which forms auditory tube, middle ear

Branchial Clefts 2, 3, 4

Derivatives

• Cervical Sinus

Branchial Pouch 2 derivative 

• palatine tonsil

Branchial Pouch 3 Derivative

• inferior parathyroid, thymus

Branchial Pouch 4 Derivative

• superior parathyroid 

Branchial Pouch 5 derivative

• ultimobranchial body (part of thyroid)

Cervical Sinus defects

• usually degenerates without leaving a trace
• may persists as cervical cyst or cervical fistula
• fistula may retain connections to outside world(external fistula) or pharynx(internal fistula)

DiGeorge Syndrome

• affects regulation of the formation of branchial arches and is pronunced in the first and second arch
• caused by deletion on chromosome 22 and effects other organ systems
• thymus and parathyroids are absent or severerly deformed
• cleft palate is common, facial features arches low set ears, wide set eyes, no philtrum and long face
• heart defects (VSD, tetralogy of fallot)
• learning disabilities and delayed speach

Innervation of Tongue

• motor is CN XII
• General Sense for anterior is CN V3
• Special sense for anterior is CN VII
• general and special sense for posterior part of the tongue is CN IX

Ankyloglossia

• condition where the tongue is not fully released from the floor of the mouth (often by extension of the fenulum to the tip of the tongue(midline flap))
• 1 in 300 births
• surgery not usually necesarry because frenulum stretches after birth
• tongue-tied

Thymus development

• forms from the third left and right paryngeal pouch
• loses its connection to the pouch and migrates inferior and medial
• left and right glandular masses merge
• thmus grows through puberty and is important lymphoid organ 
• dissapears after that

Parathyroid Gland Development

• inferior parathyroid forms from third pharyngeal pouch
• superior parathyoid forms from the fourth pharyngeal pouch
• gland loses its connection with the pouch and is drawn inferiorally with the thymus
• finish their migration in the neck, resting with the thyroid gland
• may not complete journy and can sometimes be found above the thyroid gland, commonly near the bifurcation of the carotids

Thyroid Development

• forms as a blind pouch, the thyroglossal duct, which migrates inferiorly from the posterior area of the tongue in the midline;anterior to the larynx, and eventually embraces the inferior larynx anteriorly and laterally
• the thyroglossal duct may persist in adult life as a pyramidal lobe of the thyroid 
• foramen cecum is postnatal remnant of thyroglossal duct on tongue
• tissue from ultimobranchial body(pharyngeal pouch 5) also contributes
• thymic tissue may be found as small accessory thymic glands in neck

Thyroglossal Cysts

• remnants of the thyroglossal duct
• given that the thyroid forms in the midline, these cysts are always found near the midline
• cysts are liable to the same diseases as the glands themselves

Larynx development

• pharyngeal arch IV and VI from thyroid, cricoid, arytenoid, epiglottis
• arch IV froms cricothyroid muscle and all other intrinisic muscles is arch VI
• endoderm of foregut forms all epithelium as well as vocal and vestibular folds

Thyroglossal duct

• forms the thyroid gland
• on the boundaries btw arch 1 and III in the floor of the mouth