Embryology of the Head and Neck

Question 1

during the first 10 weeks of development what cradles the base of the skull?
-what forms at the end of this period

Answer 1

cartilaginous neurocranium

-flat bones of cranial vault start to form as part of membranous neurocranium

Question 2

2 parts of the viscerocranium or facial bones

Answer 2

cartilaginous: 1st branchial arch: meckel’s
2nd branchial arch: reichert’s
3,4,6 branchial arches

membranous: maxillary prominence of 1st branchial arch
mandibular prominence of 1st branchial arch

Question 3

apert syndrome

Answer 3

premature fusion of coronal sutures

-tower skull appearance

Question 4

cranioschisis

Answer 4

failure of occipital and parietal bones to completely form or close
-associated with arreste4d brain development and rudimentary forebrain (anacephaly)

Question 5

macrocephaly

Answer 5

enlarged cranium secondary to hydrocephaly

Question 6

week 4 development of face, stomodeum

Answer 6

separated from the endodermal foregut by oropharyngeal membrane

Question 7

what induces the evagination of the ectoderm to form the stomodaeum

Answer 7

the primitve pharynx

Question 8

frontalnasal prominence forms what

Answer 8

forehead, dorsum and apex of nose

• portion of skin ectoderm thickens = nasal placodes
• invagination of nasal placodes = lateral and medial nasal prominences

Question 9

what are the nasal prominences formed by

Answer 9

the proliferation of the mesenchyme beneath the medial and lateral edges of the nasal placodes

Question 10

what does the lateral nasal prominence form

Answer 10

the alae of the nsoe

Question 11

what does the medial nasal prominence form

Answer 11

middle part of nose, mdeial upper lip and philtrum

dorsum of nose

Question 12

what forms the primary palate

Answer 12

the posterior portion of the intermaxillary segment

Question 13

how does the nasal septum form

Answer 13

midline down growth of fused medial nasal prominences

Question 14

secondary palate develops as ___ develops

will develop ___ ____ that fuse with ____

Answer 14

tongue

palatal shelves, primary plate

Question 15

how do nasal sacs form

Answer 15

nasal placodes invaginate to form nasal pits, enlarge to form nasal sacs (primitive nasal cavities)

Question 16

what is the remaining membrane between the nasal sacs and oral cavity called

Answer 16

oronasal membrane, later ruptures to open the nasopharynx to the oropharynx (primitive choanae

Question 17

formation of the nasolacrimal duct

Answer 17

lateral nasal prominence and maxillary prominence form furrow, ectoderm in floor thickens to form a cord
-separates from surface and canalizes to form nasolacrimal duct

Question 18

what does the buccopharyngeal membrane mark

Answer 18

its the line marking the anterior 2/3 of oral cavity (ectoderm) and posterior 1/3 (endoderm)

Question 19

what is an oblique facial cleft due to

Answer 19

failure of lateral nasal prominence and maxillary prominence to fuse
-associated with cleft chin

Question 20

what do the maxillary prominences form

Answer 20

lateral parts of upper lip and jaw

-secondary palate or palatine shelves

Question 21

strucutres from branchial arch III innervated by what

Answer 21

glossopharyngeal nerve

Question 22

what happens when the mandibular prominences fail to fuse

Answer 22

a cleft chin will result

Question 23

what fuses to separate the nasal cavity from the oral cavity

Answer 23

the secondary palate

Question 24

if the intermaxillary prominence does not fuse with maxillary swelling what do you get

Answer 24

cleft lip or palate

Question 25

what is the landmark between the primary and secondary palates -what does it determine

Answer 25

the incisive foramen | -determines anterior from posterior cleft deformities

Question 26

what is the secondary palate formed by

Answer 26

lateral palatine processes or palatine shelves on inner aspect of maxillary swellings

Question 27

nasal septum develops between 2 ___ ___ and descends from the ___ ___ and merges with ___ ___

Answer 27

nasal sacs frontal prominence palatine shelves

Question 28

how is an anterior cleft deformity happen

Answer 28

failure of the medial nasal and maxillary swellings to fuse

Question 29

how does posterior cleft deformity happen

Answer 29

palatine shelves do not fuse

Question 30

bilateral cleft lip

Answer 30

failure of medial nasal processes to fuse with the maxillary swellings

Question 31

macrostomia and microstomia

Answer 31

dysfusion of maxillary and mandibular swellings

Question 32

median cleft lip and bifid nose

Answer 32

failure of medial nasal prominences to fuse

Question 33

what is exposed in an oblique facial cleft

Answer 33

nasolacrimal duct

Question 34

the branchial arches are under the induction of what

Answer 34

migratory neural crest cells

Question 35

skeletal strcuture associated with branchial arch I

Answer 35

incus, malleues

Question 36

branchial groove associated with branchial arch I

Answer 36

tympanic membrane | external auditory meatus

Question 37

muscle with arch III

Answer 37

stylopharyngeus

Question 38

skeletal structure arch III

Answer 38

hyoid

Question 39

artery arch III

Answer 39

stem of internal carotids

Question 40

skeletal structure arch IV

Answer 40

laryngeal cartilages

Question 41

artery arch IV

Answer 41

left: aortic arch right: subclavian vein

Question 42

first arch syndrome

Answer 42

treacher collins syndrome - imparied growth of midface - hearing loss in 40-50% of people - small chin, enlarged nose, cleft palate and possibly lip

Question 43

first branchial puch forms what eventually

Answer 43

eustachian tube and tympanic cavity

Question 44

second branchial pouch forms what

Answer 44

tongue (root)

Question 45

third branchial pouch forms what

Answer 45

tongue

Question 46

pouch 1 derivative

Answer 46

tubotympanic recess

Question 47

pouch 2 derivative

Answer 47

palatine tonsils

Question 48

pouch 3 derivatives

Answer 48

inferior parathyroids | thymus

Question 49

pouch 4 derivatives

Answer 49

superior parathyroids and ultimobranchial body

Question 50

what does the first cleft form

Answer 50

the external auditory meatus

Question 51

what happens to the rest of the clefts besdies the first

Answer 51

the second arch expands and fuses with the cardiac eminance to cover remaining clefts = transient cervical sinus

Question 52

abnormal cysts can be produced by ____ or ___

Answer 52

lateral cervical sinus or first pharyngeal cleft - isolated cervical cyst - cervical cyst with external fistula - cervical cyst with internal fistula

Question 53

sites for aural and cervical cysts and fistulae

Answer 53

aural cyst anterior to the ear | lateral cervical cyst located anterior to SCM

Question 54

what is the thyroglossal duct

Answer 54

connects the migrating thyroid to tongue at foramen cecum | -ductal remnants may persist and form cysts

Question 55

glandular part of thyroid that persists along midline

Answer 55

pyramidal lobe

Question 56

formation anterior 2/3 of tongue

Answer 56

lateral lingual swellings (arch 1) overgrow the median tuberculum impar, and fuse midline

Question 57

formation of posterior third of tongue

Answer 57

overgrowth of coula (median mass arch II) by hypobranchial eminence of 3rd arch

Question 58

what demarcates the anterior from posterior portions of the tongue

Answer 58

sulcus terminalis