Embryology: Oral Biology

Question 1

What is growth?

Answer 1

Physical increase in size or number. A differential process with some parts growing more rapidly than others.

Question 2

What is development?

Answer 2

An increase in the degree of organization and/or functional complexity.

Question 3

What kind of process is development?

Answer 3

It is a physiologic and behavioral process.

Question 4

What is craniofacial morphogenesis?

Answer 4

A complex series of events leading to the formation of the head and face.

Question 5

Between what weeks is it the critical period for formation of the face and mouth?

Answer 5

The fourth and fourteenth week of intrauterine life.

Question 6

What are the stages of cleavage?

Answer 6

1) Fertilization
2) Zygote
3) 2-cell
4) 4-cell
5) 8-cell
6) Morula

Question 7

What is an embryoblast?

Answer 7

When the cells in the morula migrate to one side of the cell.

Question 8

What is a trophoblast?

Answer 8

When that accumulated cells of the embryoblast attach to the uterine wall.

Question 9

What are the embryologic stages?

Answer 9

1) Proliferative period (0-2 weeks)
2) Embryonic period (2-8 weeks)
3) Fetal period (8 weeks to 9 months)

Question 10

What happens in week 1?

Answer 10

Formation of the bilaminar disc from cells of the zygote. Differentiation of ectoderm and endoderm.

Question 11

What happens in week 2?

Answer 11

Gastrulation phase leads to formation of mesoderm, resulting in a trilaminar disc.

Question 12

What happens in week 3?

Answer 12

• Neuralation stage

* Formation of neural tube from the neural plate.

Question 13

What does the neuralation stage mark?

Answer 13

It marks the beginning of formation of the CNS.

Question 14

What does the formation of the neural tube lead to?

Answer 14

It leads to differentiation of neural crest cells which migrate laterally and ventrally towards the area of the future face.

Question 15

What are the symptoms of Fetal Alcohol Syndrome?

Answer 15

• effects stage 1 - intial organization of germ layers.
• first three ventricles of brain fail to separate
• olfactory placodes too close together (deficient median nasal prominence)
• varies from total absence of nose to midface deficiency.

Question 16

What is foregut?

Answer 16

Upper part, becomes digestive tube from the throat to duodenum.

Question 17

What is the midgut?

Answer 17

Middle part, becomes small intestine, cecum, ascending colon, most of transverse colon.

Question 18

What is the hindgut?

Answer 18

Becomes descending colon, sigmoid colon, and rectum of the large intestine.

Question 19

What are the 5 main processes to form the face?

Answer 19

1) Frontonasal process
2) Maxillary process
3) ???????/
4) ??????/
5) ????????

Question 20

When does the oral pit first appear?

Answer 20

Week 4.

Question 21

How and when does the stomodeum (oral cavity) develop?

Answer 21

A pit development between the brain and heart. Week 4.

Question 22

What week does the oropharyngeal membrane rupture?

Answer 22

Week 5.

Question 23

How does the oropharynx form?

Answer 23

•The oropharyngeal membrane opens the oral cavity to tubular foregut.

Question 24

How does cheeks form?

Answer 24

•The mandibular arch grows laterally to oral pit and will develop into the maxillary process.

Question 25

When and how do you hear the first heart beats?

Answer 25

Blood being forced through the vessels supplying face, neck and brain. During week 4.

Question 26

What makes up the frontal prominence?

Answer 26

Forehead area, above stomodeum and mandibular process of mandibular arch. After 4 weeks, evidence of nasal pits, beginning of the nasal cavity.

Question 27

What is an important aspect of week 4?

Answer 27

The migration of neural crest cells to make the five processes.

Question 28

Where do most major malformations of the craniofacial complex originate during transformation of the branchial apparatus into its adult derivative?

Answer 28

Branchial arches.

Question 29

What does the branchial arches greatly contribute to?

Answer 29

To the formation of the head and neck region.

Question 30

What happens in week 5-6?

Answer 30

* facial processes continue to migrate * development of nose and nostrils * eyes and external ears become more evident * manidble begins ossification during late sixth week.

Question 31

What happens specifically in week 5-6 in the face?

Answer 31

The nasal prominences gradually separate from the maxillary prominence by deep furrows.

Question 32

What does the nasal pit do in week 5-6?

Answer 32

It invaginates and forms the lateral and medial nasal processes.

Question 33

When does prenatal cleft lip happen?

Answer 33

Around week 6-7.

Question 34

What is hemifacial microsomia?

Answer 34

* Lack of tissue on the affected side of the face * Usually in the area of the ramus of the mandible and the ear. * early loss of neural crest cells * cleft lip/palate and renal abnormalities can result

Question 35

What is hemifacial microsomia?

Answer 35

* Lack of tissue on the affected side of the face * Usually in the area of the ramus of the mandible and the ear. * early loss of neural crest cells * cleft lip/palate and renal abnormalities can result

Question 36

How is each arch separated?

Answer 36

By vertical grooves.

Question 37

Within the pharynx, what are the grooves that separate each groove called?

Answer 37

Pharyngeal pouches.

Question 38

What is the 1st arch called and comprised of?

Answer 38

The mandibular arch. It will form bony mandible, muscles of mastication, nerves, and blood supply.

Question 39

What is the 2nd arch called and comprised of?

Answer 39

The Hyoid arch. It forms the facial muscles, vessels, and hyoid bone.

Question 40

What does the 3rd, 4th and 5th arches do?

Answer 40

Paired right and left bars that are divided before they reach the midlineby the presence of bulging heart.

Question 41

When does arches 2-5 develop?

Answer 41

Between the fourth and seventh prenatal week.