Embryology

Question 1

what are the three components of the pharyngeal apparatus?

Answer 1

1. Arch (mesenchymal tissue)
2. Cleft (ectoderm)
3. Pouch (endoderm)

Question 2

what separates arches?

Answer 2

clefts and pouches

Question 3

what is each arch associated with?

Answer 3

artery
nerve
vein

Question 4

cranial nerve of arch 1

Answer 4

trigeminal nerve (CNV2 and V3)

Question 5

cranial nerve of arch 2

Answer 5

facial nerve (CNVII)

Question 6

cranial nerve of arch 3

Answer 6

glossopharyngeal nerve (CNIX)

Question 7

cranial nerves of arch 4 and 6

Answer 7

both CNX (vagus nerve)

• 4 is superior laryngeal branch
• 6 is recurrent laryngeal branch

Question 8

what does the 2nd-4th cleft form?

Answer 8

cervical sinus (if contact not lost then cervical cysts form)

Question 9

what does the 2nd pouch form?

Answer 9

palatine tonsil

Question 10

where are cervical (branchial) cysts and fistulas seen?

Answer 10

anterior border of sternocleidomastoid (enlarge in childhood associated with persistence of cervical sinus)

Question 11

describe formation of the nasolacrimal groove

Answer 11

lies between maxillary and lateral nasal prominence
solid epithelial cord in floor of the groove
cord detaches from the ectoderm
canalisation forms nasolacrimal duct

Question 12

formation of cleft lip

Answer 12

mal-union between the primary palate and upper lip (medial nasal prominence still connected)

Question 13

why can babies eat and breath at the same time?

Answer 13

the distance between the epiglottis and maxilla is very small and the oropharynx is not fully developed yet

Question 14

formation of cleft palate

Answer 14

floating of the primary palate (potential for nasolacrimal clefting)