H&N Embryology I

Question 1

special sense placodes are derived from what germ layer?

Answer 1

ectoderm (surface ectoderm)

Question 2

ectomesenchyme is derived from what germ layer?

Answer 2

ectoderm (neuroectoderm-neural crest cells)

Question 3

somitomeres & somites are derived from what germ layer?

Answer 3

mesoderm (paraxial mesoderm)

Question 4

What CNs are associated with special sense placodes?

Answer 4

CN I, II, VIII

Question 5

What CNs are associated with ectomesenchyme?

Answer 5

CN V

Question 6

What CNS are assoc w/ somitomeres and somites?

Answer 6

CN III, IV, V3, VI, VII, IX, X, XI, XII

Question 7

sensory innervation and primordia of face

Answer 7

CN V and ectomesenchyme (neural crest cells)

Question 8

sensory innervation and primordial of posterior of head

Answer 8

spinal nerves, like rest of the body and somites (paraxial mesoderm)

Question 9

two parts of the cranium

Answer 9

1. neurocranium - encloses the brain, has two parts a. calvaria b. basicranium 2. viscerocranium - facial skeleton, encloses gut tube derivatives

Question 10

how does the calvaria form?

Answer 10

intramembranous ossification of ectomesenchyme (frontal bone) or paraxial mesoderm (parietal or occipital bones)

Question 11

how does the basicranium form?

Answer 11

endochondral ossification of sclerotome portion of occipital somites

Question 12

when do pharyngeal arches form?

Answer 12

4th or 5th week

Question 13

Arch 0

Answer 13

frontonasal prominence

Question 14

Arch 1a

Answer 14

maxillary prominence of 1st arch

Question 15

Arch 1b

Answer 15

mandibular prominence of 1st arch

Question 16

Contents of each pharyngeal arch (4)

Answer 16

(1) cartilage (2) muscle (3) cranial nerve (4) aortic arch artery

Question 17

what does the cartilage in 1st, 2nd, 3rd arches derive from?

Answer 17

ectomesencyhme

Question 18

what does the cartilage in 4th-6th arches derive from?

Answer 18

lateral plate mesoderm

Question 19

Definitive muscles formed from pharyngeal arches

Answer 19

1st - muscles of mastication, 2nd- muscles of facial expression, 3rd - stylopharyngeus muscle, 4th-6th laryngeal muscles

Question 20

sensory pretrematic branches (4)

Answer 20

(1) opthalmic division of trigeminal nerve –> arch 0 (2) chorda tympani (CN VII) –> taste fibers in anterior 2/3 of tongue (1st arch) (3) tympanic branch of glossopharyngeal nerve (CN IX) –> middle ear and auditory tube (2nd arch) (4) internal laryngeal branch of vagus nerve (CN X) –> sensory innervation to larynx superior to vocal cords (4th arch)

Question 21

Pharyngeal arch artery derivatives

Answer 21

1st - mostly disappears (forms small part of maxillary artery)
2nd- mostly disappears
3rd - common carotid a, proximal internal carotid a
4th - aortic arch, proximal right subclavian a.
6th - proximal part of pulmonary arteries, ductus arteriosus

Question 22

pharyngeal arch table

Answer 22

slide 23 - memorize!

Question 23

cervical sinus

Answer 23

formed by remnants of the second, third, and fourth pharyngeal clefts –> normally obliterated

Question 24

adult derivatives from frontonasal prominence

Answer 24

forehead, nose, philtrum, primary palate

Question 25

adult derivatives from maxillary prominence

Answer 25

upper cheek, maxilla, zygoma, lateral portion of upper lip, secondary palate

Question 26

adult derivatives from mandibular prominence

Answer 26

lower lip, lower cheek, mandible

Question 27

Cranial nerves assoc w/ arches

Answer 27

1st arch: CN V1 - opthalmic division of trigeminal nerve
2nd arch: CN VII - facial
3rd arch: CN IX - glossopharyngeal
4th-6th arch: CN X - vagus