Introductory Embryology, Oral-Facial Development and Associated Developmental Abnormalities

Question 1

What are the stages of human development?

Answer 1

-Proliferation period (0-3 weeks)
-embryonic period (3-8 weeks)
-fetal development period (9 weeks to term)

Question 2

What forms after an ovum is fertilized?

Answer 2

zygote

Question 3

What does mitotic cleavage of a zygote form?

Answer 3

blastomere

Question 4

What is the stage of >32 blastomeres called?

Answer 4

morula

Question 5

What happens at the 64 cell stage?

Answer 5

morula develops an internal blastocytstic cavity and becomes a blastocyst

Question 6

What is a cyst?

Answer 6

a mass lined with usually epithelial tissue with a hollow cavity
(can be fluid filled)

Question 7

What is an embryoblast ?

Answer 7

cell stage in development after the blastocyst develops an inner cell mass

Question 8

When does implantation of embryoblast occur?

Answer 8

starting at day 4 and usually done by day 10

Question 9

What are syncytiotrophoblasts?

Answer 9

finger like projections that help the embryoblast implant into the wall of the uterus

Question 10

What is the bilaminar embryonic disc?

Answer 10

two layers of cells that form in the inner cell mass

Question 11

When does the bilaminar embryonic disc form?

Answer 11

when the embryoblast starts getting engulfed into the uterine wall

Question 12

What does the outer cell mass become?

Answer 12

cytotrophoblast and syntrophoblast layers
(precursors to the placenta)

Question 13

What does the epiblast layer of the bilaminar embryonic disc become?

Answer 13

ectoderm and mesoderm

Question 14

What does the hypoblast layer of the bliaminar disc become?

Answer 14

endoderm

Question 15

What is the Heuser’s membrane?

Answer 15

the internal lining of the blastocyst cavity

Question 16

What is the blastocyst cavity become?

Answer 16

yolk sac

Question 17

What is the third cavity that forms during development?

Answer 17

chorionic cavity

Question 18

What are the three distinct embryonic germ layers?

Answer 18

endoderm
mesoderm
ectoderm

Question 19

What is formed during the 3rd week of development from the bilaminar embryonic disc?

Answer 19

primitive streak
notochord
neural tube

Question 20

How is the notochord formed?

Answer 20

pre-notochordal cells invaginate within the primitive node and migrate toward the cephalad until the reach the prechordal plate
-they detach themselves from the ectodermal layer to line within the mesoderm forming the notochord

Question 21

What is the order of steps to make the notochord?

Answer 21

primitive node -> notochordal process -> notochord

Question 22

What is the function of the notochord?

Answer 22

functions as a primitive skeletal support of the embryo around which the axial skeleton forms later

Question 23

What does the notochord induce the formation of?

Answer 23

the somites
-precursors of the vertebral column, ribs, associated back muscles, and overlying dermis

Question 24

What are the three types of mesoderm?

Answer 24

-paraxial
-intermediate
-lateral plate

Question 25

What are the two types of lateral plate mesoderm?

Answer 25

-parietal -visceral

Question 26

What does the paraxial mesoderm form?

Answer 26

somites

Question 27

What does the intermediate mesoderm form?

Answer 27

the urogenital system

Question 28

What does the parietal segment of the lateral plate mesoderm form?

Answer 28

mesothelial (serous) membranes that cover the peritoneal, pleural, and pericardial cavities

Question 29

What does the visceral segment of the lateral plate mesoderm form?

Answer 29

the thin serous membranes that cover individual organs, stomach, pancreas, spleen, and other organs

Question 30

What are the derivatives of ectoderm?

Answer 30

-epidermis, hair, and nails -epithelium of the oral and nasal cavities and paranasal sinuses -salivary and endocrine glands -nervous system -tooth enamel

Question 31

What are the derivatives of the endoderm?

Answer 31

GI tract epithelium and associated glands

Question 32

What is spina bifida?

Answer 32

developmental defect that occurs when the neural tube does not close properly -due to folic acid deficiency

Question 33

What is meningocele?

Answer 33

extrusion of dura and arachnoid mater

Question 34

What is meningomyelocele?

Answer 34

extrusion of neural tissue plus all three meninges

Question 35

What is meningoencephalocele?

Answer 35

extrusion of a ventricular cistern plus neural tissue

Question 36

What is anencephaly?

Answer 36

fatal defect characteristics by lack of development of the cranium and brain

Question 37

What are other names for neural crest cells?

Answer 37

ectomesenchyme and neuroectoderm

Question 38

What are some of the things that cranial neural crest cells form ?

Answer 38

-odontoblasts -truncocoronal septum -pharnygeal arch and cartilage -dermis and epidermis of the head and neck

Question 39

What are some things that spinal neural crest cells form?

Answer 39

-preaortic ganglia -adrenal medulla -dorsal root ganglia -chain ganglia

Question 40

What are some things that are formed from both cranial and spinal neural crest cells?

Answer 40

-schwann cells -glial cells -arachnoid and pia mater -enteric ganglia

Question 41

When do the pharyngeal arches begin forming?

Answer 41

day 28 of development

Question 42

What are associated with each level of pharyngeal arches?

Answer 42

blood vessel, cranial nerves, and cartilage

Question 43

What does the 1st branchial groove form?

Answer 43

external auditory canal

Question 44

What does the 1st branchial pouch form?

Answer 44

eustachian tube

Question 45

What does the 2nd branchial pouch form?

Answer 45

palatine tonsils

Question 46

What does the 3rd branchial pouch form?

Answer 46

inferior parathyroids/thymus

Question 47

What does the 4th branchial pouch form?

Answer 47

superior parathyroids/ultimobranchial body

Question 48

What happens to the relative size of the fetal head during development?

Answer 48

the head stays around the same size but the body gets larger -means the percentage of the fetus that is head gets smaller

Question 49

What are the four processes of the face that start lateral and move toward the medial to form the face?

Answer 49

-mandibular process -maxillary process -lateral nasal process -median nasal process

Question 50

What is the remanent of the face of the lateral processes coming together?

Answer 50

the filtrum of the lip

Question 51

What can happen if the processes do not meet properly?

Answer 51

cleft lip or palate

Question 52

When does fusion of the maxillary and medial nasal processes usually occur?

Answer 52

5-6 weeks gestation

Question 53

when does fusion of the palatine shelves occur?

Answer 53

begin during the 8th week and is completed in the 12th week

Question 54

What percentage of clefts are combined cleft lip/palate?

Answer 54

45%

Question 55

What percentage of clefts are just cleft palate?

Answer 55

30%

Question 56

What percentage of clefts are just cleft lip?

Answer 56

25%

Question 57

Incidence of cleft lip/palate in Chinese, Japanese, and Native American populations

Answer 57

1 in 500

Question 58

Incidence of cleft lip/palate in Caucasian populations

Answer 58

1 in 700

Question 59

Incidence of cleft lip/palate in African American populations

Answer 59

1 in 500

Question 60

Incidence of cleft lip/palate in all populations

Answer 60

1 in 2500

Question 61

Is there a genetic aspect of cleft lip/palate?

Answer 61

yes sort of -if you have one child with cleft lip/palate, there is a 40% chance of having a second child with it

Question 62

What are some drugs that can cause cleft lip/palate ?

Answer 62

ethanol, tetracycline, dilantin, lithium, methotrexate, warfarin, thalidomide, androgens, progesterone, and retinoic acid

Question 63

What are some chemicals that can cause cleft lip/palate?

Answer 63

methylmercrury, polychlorinated biphenyls

Question 64

Can radiation cause cleft lip/palate?

Answer 64

yes

Question 65

Where can a nasopalatine duct cyst form?

Answer 65

at the fusion between palatine shelves and primary plate

Question 66

Where do lateral cervical cyst/branchial fistuals form?

Answer 66

along the line of the sternocleidomastiod muscle

Question 67

What pharyngeal arches help to form the tongue?

Answer 67

1- forms the anterior part of the tongue and contributes CN 5 2- provides some innervation 3 and 4- both help to form the posterior tongue

Question 68

What is the intermediate and adult structure the come form the branchial arch 1?

Answer 68

intermediate -median tongue bud -foramen cecum -lateral lingual swellings adult -overgrown my lateral lingual swellings -origin of the thyroid ectoderm -anterior 2/3 of tongue

Question 69

What is the intermediate and adult structure the come form the branchial arch 2?

Answer 69

intermediate -copula/tuberculim impar adult -overgrown by the hypobranchial eminence

Question 70

What is the intermediate and adult structure the come form the branchial arch 3?

Answer 70

intermediate -hypobranchial eminence adult -posterior 1/3 of tongue

Question 71

What is the intermediate and adult structure the come form the branchial arch 4?

Answer 71

intermediate -minor contributions to the hypobranchial eminence adult -none

Question 72

What cranial nerve innervates branchial arch 1?

Answer 72

CN V (trigeminal)

Question 73

What cranial nerve innervates branchial arch 2?

Answer 73

CN VII (facial)

Question 74

What cranial nerve innervates branchial arch 3?

Answer 74

CN IX (glossopharyngeal)

Question 75

What cranial nerve innervates branchial arch 4?

Answer 75

CNX (vagus)

Question 76

What cranial nerve innervates branchial arch 6?

Answer 76

CN XII (hypoglossal)

Question 77

What does the trigeminal nerve do for the tongue?

Answer 77

sensory to the anterior 2/3

Question 78

What does the facial nerve do for the tongue?

Answer 78

special sensory (taste) to anterior 2/3 via the chorda tympani branch

Question 79

What does the glossopharyngeal nerve do for the tongue?

Answer 79

sensory to the posterior 1/3

Question 80

What does the vagus nerve do for the tongue?

Answer 80

sensory to the extreme posterior 1/3 via the superior laryngeal branch

Question 81

What does the hypoglossal nerve do for the tongue?

Answer 81

motor to all of the tongue muscles

Question 82

What is the median rhomboid glottitis?

Answer 82

was thought to present a portion of the tuberculum impar (branchial arch II) that persists, but is now considered to be a result of a fungal infection

Question 83

How does a thyroglossal duct cyst form?

Answer 83

failure of thyroglossal duct to involute

Question 84

Where does the thyroid start forming?

Answer 84

near the foramen cecum of the tongue -must move inferiorly past the epiglottis, hyoid bone, thyroid cartilage, and the cricoid cartilage to make it to the correct place

Question 85

What is a ectopic lingual thyroid?

Answer 85

when the thyroid does not move inferiorly and remains on the posterior part of the tongue

Question 86

What cartilages forms from the first pharyngeal arch?

Answer 86

Meckel's cartilage Mandible maleus incus

Question 87

What cartilage and bone forms from the second pharyngeal arch?

Answer 87

reichart's cartilage stapes styloid process stylohyoid ligament lesser horn of hyoid

Question 88

What cartilage and bone forms from the third pharyngeal arch?

Answer 88

greater horn of hyoid

Question 89

What cartilage and bone forms from the fourth pharyngeal arch?

Answer 89

thyroid cartilage

Question 90

What are the segments that are combined to form the ear?

Answer 90

there are 6 auricular hillocks that come together to form the ear -sometimes there are more than 6 or less than 6 depending on formation