Craniofacial Embryology

Question 1

when do head and neck develop

Answer 1

weeks 4-8

Question 2

what embryonic structure do the head and neck develop from

Answer 2

pharyngeal apparatus

Question 3

pharyngeal apparatus is sometimes called

Answer 3

branchial apparatus

Question 4

3 components of pharyngeal apparatus

Answer 4

clefts, arches, pouches

Question 5

on what day do the 5 pairs of pharyngeal arches start to form

Answer 5

22

Question 6

what separates the pharyngeal arches externally

Answer 6

clefts

Question 7

what are pharyngeal clefts composed of

Answer 7

ectoderm

Question 8

what separates pharyngeal arches internally

Answer 8

pouches

Question 9

what are pharyngeal pouches composed of

Answer 9

endoderm

Question 10

outer covering of pharyngeal arch is composed of

Answer 10

ectoderm

Question 11

inner lining of pharyngeal arch is composed of

Answer 11

endoderm

Question 12

core of pharyngeal arch is composed of

Answer 12

mesenchyme derived from mesoderm and neural crest

Question 13

what elements of pharyngeal arch are derived from neural crest

Answer 13

cartilage, connective tissue, and arch-associated cranial nerve

Question 14

what elements of pharyngeal arch are derived from mesoderm

Answer 14

skeletal muscle and an aortic arch artery

Question 15

2 components of first pharyngeal arch

Answer 15

maxillary process, mandibular process

Question 16

maxillary process becomes

Answer 16

maxilla, zygomatic bones

Question 17

mandibular process becomes

Answer 17

mandible, middle ear structures (incus, malleus)

Question 18

incus and malleus are derived from what embryonic structure

Answer 18

Meckel’s cartilage

Question 19

what skeletal muscles are derived from first pharyngeal arch

Answer 19

muscles of mastication, anterior digastric, mylohyoid, tensory tympani, anterior 2/3 of tongue

Question 20

what cranial nerve is associated with first pharyngeal arch

Answer 20

mandibular and maxillary divisions of trigeminal nerve

Question 21

what artery is associated with first pharyngeal arch

Answer 21

portion of maxillary

Question 22

what embryonic structure is derived from second pharyngeal arch

Answer 22

Reichart’s cartilage

Question 23

What does Reichart’s cartilage give rise to?

Answer 23

stapes bone, styloid process of temporal bone, part of the hyoid bone

Question 24

what skeletal muscles are derived from second pharyngeal arch

Answer 24

muscles of facial expression, stapedius, stylohyoid, posterior digastric

Question 25

what cranial nerve is associated with second pharyngeal arch

Answer 25

facial nerve

Question 26

what embryonic arteries are derived from second pharyngeal arch and what artery does one of them become

Answer 26

stapedial and hyoid (becomes branch of internal carotid)

Question 27

bones formed from third pharyngeal arch

Answer 27

part of hyoid

Question 28

muscles formed from third pharyngeal arch

Answer 28

stylopharyngeus

Question 29

arteries formed from third pharyngeal arch

Answer 29

common carotid arteries and proximal internal carotid arteries

Question 30

cranial nerve associated with third pharyngeal arch

Answer 30

glossopharyngeal

Question 31

4th and 6th pharyngeal arches share what nerve

Answer 31

vagus

Question 32

4th arch is associated with what branch of vagus nerve

Answer 32

superior laryngeal

Question 33

6th arch is associated with what branch of vagus nerve

Answer 33

recurrent laryngeal

Question 34

4th and 6th arches fuse to form

Answer 34

laryngeal cartilages and muscles

Question 35

list the laryngeal cartilages

Answer 35

thyroid, cricoid, arytenoid, corniculate, cuneiform

Question 36

4th arch forms what muscles

Answer 36

cricothyroid, levator palatini, pharyngeal constrictors

Question 37

6th arch forms what muscles

Answer 37

intrinsic muscles of larynx except cricothyroid

Question 38

4th arch artery becomes

Answer 38

arch of aorta on left and proximal right subclavian

Question 39

6th arch artery becomes

Answer 39

proximal pulmonary arteries and ductus arteriosus

Question 40

derivatives of first pharyngeal cleft

Answer 40

external auditory meatus, external part of tympanic membrane

Question 41

derivatives of first pharyngeal pouch

Answer 41

internal part of tympanic membrane, tympanic cavity, and eustachian tube

Question 42

derivatives of second pouch

Answer 42

palatine tonsil

Question 43

derivatives of third pouch

Answer 43

inferior parathyroid glands and thymus

Question 44

derivatives of fourth pouch

Answer 44

superior parathyroid and ultimobranchial body

Question 45

derivatives of ultimobranchial body

Answer 45

C cells of thyroid

Question 46

how is the cervical sinus formed

Answer 46

the 2nd arch grows over and fuses with 3rd and 4th arches, the cervical sinus was the 2nd-4th clefts

Question 47

what happens if the 2nd-4th arches do not fuse completely

Answer 47

a cervical fistula or cervical cyst

Question 48

location of cervical fistulas or cysts

Answer 48

lateral, anterior to SCM, below angle of mandible

Question 49

other characteristics of cervical fistulas or cysts

Answer 49

are immobile and can occur on one or both sides

Question 50

tongue mucosa develops from

Answer 50

floor endoderm lining pharyngeal arches

Question 51

anterior 2/3 of tongue formed by

Answer 51

1st and 2nd pouches

Question 52

posterior 2/3 of tongue formed by

Answer 52

3rd and 4th pouches

Question 53

thyroid gland is developed from

Answer 53

floor endoderm of pharynx

Question 54

what is thyroglossal duct

Answer 54

a duct connecting thyroid with pharynx that breaks down

Question 55

former site of thyroglossal duct in adults

Answer 55

foramen cecum

Question 56

remnants of thyroglossal duct may persist as

Answer 56

pyramidal lobe of thyroid or fibrous strand of tissue

Question 57

thyroglossal duct cysts present as

Answer 57

midline neck mass, painless, mobile

Question 58

ectopic thyroid tissue may be found

Answer 58

along its path of descent

Question 59

most common place for ectopic thyroid tissue to be found

Answer 59

base of tongue

Question 60

face develops from

Answer 60

frontonasal process and first arch (maxillary and mandibular processes)

Question 61

how is the primary palate formed

Answer 61

a fusion between maxillary and lateral nasal processes

Question 62

how are lower lip and jaw formed

Answer 62

mandibular processes fuse in the midline

Question 63

junction between primary and secondary palate is called

Answer 63

incisive foramen

Question 64

cleft lip results from

Answer 64

incomplete fusion of maxillary process with medial nasal process

Question 65

cleft palate results from

Answer 65

incomplete fusion of palatal shelves

Question 66

when is the face formed

Answer 66

week 10

Question 67

what part of the eye derives from neuroectoderm

Answer 67

optic cup

Question 68

what part of the eye derives from ectoderm

Answer 68

lens

Question 69

optic vesicles derive from

Answer 69

neural tube

Question 70

lens develops from

Answer 70

lens placode, thickening of ectoderm

Question 71

optic cup becomes

Answer 71

retina, iris

Question 72

what is the choroid of the eye

Answer 72

layer of blood vessels and connective tissue between sclera and retina

Question 73

choroid of the eye is an extension of

Answer 73

pia mater and arachnoid

Question 74

what is the sclera

Answer 74

tough, fibrous white outer wall of the eye, continuation of dura mater

Question 75

eyelids develop as

Answer 75

ectodermal folds with a mesenchymal core from the first arch

Question 76

what is a coloboma

Answer 76

optic fissure fails to close, leaving a gap in eye structures, can be throughout the eye or localized

Question 77

what genetic mutations can congenital cataracts develop from

Answer 77

CRYSTALLIN, gap junction proteins, transcription factors

Question 78

causes of congenital cataracts

Answer 78

genetic mutations, metabolic disorders (galactosemia), congenital infections (rubella)

Question 79

what is a detached retina

Answer 79

neural retina detaches from pigmented retina

Question 80

detached retina causes

Answer 80

congenital or head trauma

Question 81

external auditory meatus develops from

Answer 81

1st cleft

Question 82

pinna/auricle develops from

Answer 82

1st/2nd arches

Question 83

auditory ossicles develop from

Answer 83

1st/2nd arches

Question 84

tympanic cavity and auditory tubes develop from

Answer 84

1st pouch

Question 85

inner ear develops from

Answer 85

ectoderm of otic placode

Question 86

what are auricular hillocks

Answer 86

proliferating ectoderm and underlying mesenchyme of 1st and 2nd arches that give rise to auricle

Question 87

auricle develops when

Answer 87

5th week

Question 88

what is conductive hearing loss

Answer 88

impaired conduction of sound to inner ear due to structural abnormalities of external ear (auricle) or middle ear

Question 89

what is microtia

Answer 89

small auricle due to suppressed growth of hillocks

Question 90

what is anotia

Answer 90

lack of auricle due to suppressed growth of hillocks

Question 91

what is macrotia

Answer 91

large auricle due to overgrowth of hillocks

Question 92

preauricular tags or pits are caused by

Answer 92

accessory hillocks

Question 93

defects of external auditory meatus include

Answer 93

atresia and stenosis

Question 94

microtia is associated with what genetic disorders

Answer 94

bronchio-oto-renal (BOR), CHARGE, Treacher Collins, trisomy 21 and 18

Question 95

microtia is associated with what teratogens

Answer 95

alcohol, retinoic acid

Question 96

macrotia is associated with

Answer 96

Fragile X syndrome, the most common cause of mental retardation in males

Question 97

middle ear defects develop from

Answer 97

defects with malleus, incus, stapes

Question 98

middle ear defects are associated with

Answer 98

skeletal dysplasias (achondroplasia, osteogenesis imperfecta), BOR, Treacher-Collins, OAVS

Question 99

inner ear develops from

Answer 99

otic vesicle which derives from ectodermal otic placode

Question 100

sensory ganglia of vestibulocochlear nerve develops from

Answer 100

otic placode

Question 101

sensorineural hearing loss can result from

Answer 101

defects in inner ear, vestibulocochlear nerve, auditory regions of brain

Question 102

about half of all hearing loss has what cause

Answer 102

genetic

Question 103

in utero viral infections associated with hearing loss

Answer 103

cytomegalovirus, rubella

Question 104

teratogen associated with hearing loss

Answer 104

aminoglycoside antibiotics (gentamycin, tobramycin)