Introductory Embryology, Oral-Facial Development And Associated Developmental Anomalies

Question 1

Stages of human development: (3)

Answer 1

 Proliferation Period (0-3 weeks)
 Embryonic Period (3-8 weeks)
 Fetal Development Period
(9 weeks to term)

Question 2

Fertilization of ovum yields —

Answer 2

zygote

Question 3

mitotic cleavage of zygote forms —

Answer 3

blastomeres

Question 4

more than 32 blastomeres is called a —

Answer 4

morula

Question 5

The 64 cell stage morula develops an internal blastocystic cavity and thereafter is referred to as a

Answer 5

blastocyst

Question 6

The blastocyst also develops an inner cell mass at days 6-7

and thereafter is referred to as the

Answer 6

embryoblast

Question 7

Implantation of the embryoblast in the uterine wall begins

at day - and is complete at day -

Answer 7

4, 10

Question 8

The inner cell mass of the embryoblast transitions into the

Answer 8

bilaminar embryonic disc

two layers

Question 9

Outer cell mass becomes the (2)layers which are precursor to the placenta

Answer 9

cytotrophoblast & syntrophoblast

Question 10

Epiblast Layer (2)

Answer 10

Ectoderm

Mesoderm

Question 11

Hypoblast Layer (1)

Answer 11

Endoderm

Question 12

Structures associated with the bilaminar embryonic disc (6)

Answer 12

• Epiblast Layer
• Hypoblast Layer
• Amniotic Cavity
• Blastocyst Cavity
• Syntrophoblasts
• Cytotrophobasts

Question 13

Enlargement of the amniotic cavity and migration of cells out of the hypoblast to form

Answer 13

Heuser’s membrane

Question 14

Heuser’s membrane will form the internal lining of the blastocyst cavity – now called the

Answer 14

yolk sac

Question 15

Cell layers (3)

Answer 15

 Epiblast
 Embryonic mesoderm
 Hypoblast

Question 16

Embryonic cavities (3)

Answer 16

 Amniotic
 Yolk sac
 Chorionic

Question 17

During the 3rd week of development, the bilaminar

embryonic disc is characterized by formation of the: (3)

Answer 17

Primitive Streak
Notochord
Neural Tube

Question 18

And the three distinct embryonic germ layers: (3)

Answer 18

Ectoderm (formerly the epiblast layer)
Mesoderm
Endoderm (formerly the hypoblast layer)

Question 19

Primitive Streak (3)

Answer 19

 Pit
 Node
 Groove

Question 20

steps in formation of the notochord

Answer 20

Primitive node → Notochordal Process → Notochord

Question 21

— cells invaginate within the — and migrate towards the cephalad until the reach the —. They detach themselves from the ectodermal layer to line within the mesoderm forming the —

Answer 21

Pre-notochordal
primitive node
prechordal plate
notochord

Question 22

The notochord functions as a

Answer 22

primitive skeletal support of the

embryo around which the axial skeleton later forms

Question 23

The notochord also induces formation of —, the precursors
of the vertebral column, ribs, associated back muscles and
overlying dermis.

Answer 23

somites

Question 24

formed from ectodermal cells derived from the —. The cells then migrate within the mesodermal layer to their appropriate midline position. The notochord functions as a primitive axial skeleton for the embryo, establishing symmetry and polarity of development and induction of the —

Answer 24

primitive node

somites

Question 25

Lateral Plate Mesoderm (2)

Answer 25

 Parietal |  Visceral

Question 26

``` Derivatives of Mesoderm: • Paraxial mesoderm → • Intermediate mesoderm → • Lateral plate mesoderm: Parietal mesoderm → Visceral mesoderm → ```

Answer 26

somites urogenital system mesothelial (serous) membranes that cover the peritoneal, pleural and pericardial cavities. forms the thin serous membranes that cover individual organs, e.g., stomach, pancreas, spleen, etc.

Question 27

Derivatives of Ectoderm: (5)

Answer 27

``` • Epidermis, hair and nails • Epithelium of the oral and nasal cavities and paranasal sinuses • Salivary and endocrine glands • Nervous system • Tooth enamel ```

Question 28

Derivatives of Endoderm: (1)

Answer 28

• GI tract epithelium and associated glands

Question 29

Spina Bifida

Answer 29

folic acid deficiency

Question 30

Meningocele

Answer 30

extrusion of dura and arachnoid mater

Question 31

Meningomyelocele

Answer 31

extrusion of neural tissue plus all three meninges

Question 32

Meningoencephalocele

Answer 32

extrustion of a ventricular cistern plus neural tissue

Question 33

Anencephaly

Answer 33

fatal defect characterized by lack of development of | the cranium and brain

Question 34

The clinical consequences of a defect in neural tube closure ranges from mild to fatal. --- and --- are examples of a mild defect. A slightly more severe defect is the ---. Still more severe is the ---. --- is a fatal defect.

Answer 34

``` Spina bifida meningocele meningomyelocele meningohydroencephalocele Anencephaly ```

Question 35

Neural Crest Cells | a.k.a. (2)

Answer 35

Ectomesenchyme | Neuroectoderm

Question 36

1st branchial groove ⇒

Answer 36

external auditory canal

Question 37

1st branchial pouch ⇒

Answer 37

eustachian tube

Question 38

2nd branchial pouch ⇒

Answer 38

palatine tonsils

Question 39

3rd branchial pouch ⇒

Answer 39

inferior parathyroids/thymus

Question 40

4th branchial pouch ⇒

Answer 40

superior parathyroids/ultimobranchial body

Question 41

Development of the Face: (4) processes

Answer 41

* Mandibular Process * Maxillary Process * Lateral Nasal Process * Median Nasal Process

Question 42

Defective fusion of the medial nasal process with the maxillary process results in ---. Fusion of these processes normally occurs at --- of gestation.

Answer 42

cleft lip | 5-6 weeks

Question 43

Defective fusion of the palatine shelves results in ---. Fusion of the palatine shelves normally begins during the 8th week of gestation and is completed by the ---

Answer 43

cleft palate | 12th week

Question 44

--% of all clefts are combined cleft lip/cleft palate.

Answer 44

45

Question 45

--% of cases are isolated cleft palate.

Answer 45

30

Question 46

---% of cases are isolated cleft lip.

Answer 46

25

Question 47

The incidence of cleft lip/cleft palate is: • --- in Chinese, Japanese and NativeAmerican populations • --- in Caucasian populations • --- in Afro-American populations

Answer 47

1 in 500 births 1 in 700 births 1 in 500 births

Question 48

The incidence of cleft palate alone is 1 in --- births.

Answer 48

2,500

Question 49

If one child is born with cleft lip, there is a ---% chance of a second child exhibiting the same defect.

Answer 49

40

Question 50

Known Teratogens Involved in Congenital Malformations Drugs: Chemicals: Radiation:

Answer 50

Ethanol, Tetracycline, Dilantin, Lithium, Methotrexate, Warfarin, Thalidomide, Androgens, Progesterone, Retinoic Acid Methylmercury, polychlorinated biphenyls High levels of ionizing radiation

Question 51

Nasopalatine Duct Cyst develops at the line of fusion between

Answer 51

palatine shelves and primary plate

Question 52

cervical sinus remains past

Answer 52

7th week

Question 53

Embryonic Precursor: Branchial Arch #1 Intermediate Structure: Adult Structure:

Answer 53

Median Tongue Bud Foramen Cecum Lateral Lingual Swellings Overgrown by lateral lingual swellings Origin of the thyroid ectoderm Anterior 2/3 of the tongue

Question 54

Embryonic Precursor: Branchial Arch #2 Intermediate Structure: Adult Structure:

Answer 54

Copula/Tuberculum Impar Overgrown by the hypobranchial eminence

Question 55

Embryonic Precursor: Branchial Arch #3 Intermediate Structure: Adult Structure:

Answer 55

Hypobranchial Eminence Posterior 1/3 of the tongue

Question 56

Embryonic Precursor: Branchial Arch #4 Intermediate Structure: Adult Structure:

Answer 56

Minor contributions to the hypobranchial eminence | None

Question 57

Branchial Arch: 1 Cranial Nerve: Tongue Structure:

Answer 57

Trigeminal (C-V) | Sensory to the anterior 2/3

Question 58

Branchial Arch: 2 Cranial Nerve: Tongue Structure:

Answer 58

Facial (C-VII) Special sensory (taste) to anterior 2/3 via the chorda tympani branch

Question 59

Branchial Arch: 3 Cranial Nerve: Tongue Structure:

Answer 59

Glossopharyngeal (C-IX) | Sensory to the posterior 1/3

Question 60

Branchial Arch: 4 Cranial Nerve: Tongue Structure:

Answer 60

Vegas (C-X) | Sensory to the extreme posterior 1/3 via the superior laryngeal branch

Question 61

Branchial Arch: 6 Cranial Nerve: Tongue Structure:

Answer 61

Hypoglossal (C-XII) | Motor to all tongue muscles

Question 62

Median Rhomboid Glossitis: Was thought to represent a portion of the

Answer 62

tuberculum impar (branchial arch II) that persists, but now it is considered to be a result of a fungal infection.

Question 63

Branchial Arch Cartilage (4)

Answer 63

``` I: (Meckel’s Cartilage) Mandible, Maleus, Incus II: (Reichart’s Cartilage) Stapes, Styloid Process, Stylohyoid Ligament, Lesser Horn of Hyoid III: Greater Horn of Hyoid IV: Thyroid Cartilage ```