Head and neck embryology

Question 1

when do neural crest cells migrate

Answer 1

week 3-4 of development

Question 2

2 teratogens that can destry neural crest cells

Answer 2

alcohol and retinoic acid (Accutane)

Question 3

first arch syndrome

Answer 3

• from insufficient migration of neural crest cells
• treacher collins/robin sequence
• hemifacial microsoma

Question 4

treacher collins syndrome

Answer 4

• malar hypoplasia (of zygomatic bone)
• mandibular hypoplasia
• eye, ear malformations
• autosomal dominant (also by teratogens)

Question 5

robins syndrome

Answer 5

• triad complex:
  
  • poor growth of mandible
  • high posteriorly placed tongue
  • cleft palate

Question 6

DiGeorge syndrome

Answer 6

• from pharyngeal arch 3/4 differentiation failure (neural crest cells didnt migrate)
• hypoplasia of thymus
• no parathyroid glands
• CVS defects
• facial anomalies (cleft palate)
• poor prognosis
• chrom 22 deletion
• linked to teratogens

Question 7

what does first pharyngeal pouch give rise to

Answer 7

epithelial lining of tympanic cavity and mastoid antrum (distal)

lining of eustachian tube (proximal)

Question 8

second pharyngeal pouch gives rise to

Answer 8

surface of palatine tonsil, tonsillar fossa

Question 9

third pharyngeal pouch gives rise to

Answer 9

dorsal: inferior parathyroid gland ( glandular epithelial cells that secrete PTH)
ventral: forms stroma of thymus

Question 10

fourth pharyngeal pouch gives rise to

Answer 10

dorsal: glandular cells of superior parathyroid cells
ventral: ultimobrachial body (incorporate into thyroid as parafollicular cells)

Question 11

what is derived from pharyngeal clefts

Answer 11

external auditory meatus from first cleft

Question 12

what arises from pharyngeal membranes

Answer 12

tympanic membrane from first membrane

Question 13

where are lateral cervical cysts found and what are they from

Answer 13

found laterally along SCM muscle

remnants of cervical sinus, usually below angle of jaw

Question 14

branchial fistulas

Answer 14

occur when second arch doesnt grow over arch 2,3 and 4 leaving the clefts in contact with the surface epithelium by a narrow canal (internal or external)

Question 15

when does tongue development start

Answer 15

during week 4

Question 16

what starts tongue development

Answer 16

proliferation of endoderm (and mesenchyme) of pharyngeal floor (give rise to mucus membrane)

Question 17

pharyngeal arch 1 gives rise to

Answer 17

anterior 2/3 of tongue

Question 18

root of adult tongue formed by

Answer 18

tissue of third (which overgrows second) and fourth arch endoderm

Question 19

muscles of tongue arise from

Answer 19

myotomes of occipital somites

Question 20

sensory of tongue

Answer 20

• anterior 2/3
  
  • general: lingual of CN V
  • taste: chorda tympani of CN II
• root
  
  • genreal: glossopharyngeal and vagus
  • taste: glossopharyngeal

Question 21

ankyloglossia

Answer 21

aka tongue tied

usually no intervention (frenulum stretches afer birth)

Question 22

when does thyroid gland develop

Answer 22

day 24 (first of all glands)

Question 23

when does synthesis of thyroid hormones start

Answer 23

week 12

Question 24

when should thyroglossal duct degenerate

Answer 24

week 7

(if not, gives rise to throglossal cyst)

Question 25

5 primordia of first pharyngeal arch

Answer 25

Question 26

nasolacrimal groove becomes

Answer 26

nasolacrimal duct (upper end becomes lacrimal sac)

Question 27

frontonasal process gives rise to

Answer 27

medial nasal prominences then intermaxillary segment then primary palate, philtrum, jaw with four incisor teeth

Question 28

skeletal elements pharyngeal arch 1

Answer 28

• meckel’s cartilage
• EC ossification: incus, malleus, perichondrium, sphenomandibular ligament, anterior ligament of malleus
• IM ossification: maxilla, zygomatic squamous temporal bone, mandible, portion of palatine bone

Question 29

skeletal elements pharyngeal arch 2

Answer 29

EC: stapes, styloid process, stylohyoid ligament, lesser horns and upper body of hyoid

Question 30

skeletal elements pharyngeal arch 3

Answer 30

EC: lower body and greater horns of hyoid bone

Question 31

skeletal elements pharyngeal arch 4

Answer 31

laryngeal cartilages

Question 32

skeletal elements pharyngeal arch 6

Answer 32

laryngeal cartilages

Question 33

arch artery pharyngeal arch 1

Answer 33

maxillary

Question 34

arch artery pharyngeal arch 2

Answer 34

stapedial , hyoid

Question 35

arch artery pharyngeal arch 3

Answer 35

common carotid, proximal ICA, ECA

Question 36

arch artery pharyngeal arch 4

Answer 36

left: arch of aorta, left subclavian
right: right proximal subclavian

Question 37

arch artery pharyngeal arch 6

Answer 37

pulmonary arteries, ductus arteriosus

Question 38

muscles from pharyngeal arch 1

Answer 38

muscles of mastication, mylohyoid and anterior belly of digastric, tensor tympani and tensor veli palatine

Question 39

muscles from pharyngeal arch 2

Answer 39

muscles of facial expression, posterior belly of digastric and stylohyoid, stapedius

Question 40

muscles from pharyngeal arch 3

Answer 40

stylopharyngeous

Question 41

muscles from pharyngeal arch 4

Answer 41

muscles of soft palate (except TVP), muscles of pharynx (except stylopharyngeous)

Question 42

muscles from pharyngeal arch 6

Answer 42

intrinsic muscles of pharynx, upper esophagus

Question 43

CN of pharyngeal arch 1

Answer 43

trigeminal

Question 44

CN of pharyngeal arch 2

Answer 44

facial

Question 45

CN of pharyngeal arch 3

Answer 45

glossopharyngeal

Question 46

CN of pharyngeal arch 4

Answer 46

pharyngeal branch of vagus

Question 47

CN of pharyngeal arch 6

Answer 47

recurrent laryngeal of vagus

Question 48

which germ layer gives rise to thyroid gland?

Answer 48

• nerual crest/ectoderm: parafollicular cells of thyroid
• endoderm: follicular cells of thyroid