Oral Anatomy & Histology (Review: Outcome 3)

Question 1

Embryology

Answer 1

“Embryo-“ relates to early development stages of an animal
“-ology” a science or branch of knowledge

• Important background to understanding how head and neck structures develop
• Understanding normal development allows us to:
  i. differentiate normal vs. abnormal appearances
  ii. plan for the best possible treatment(s)

Question 2

Congenital malformations

Answer 2

Developmental disturbances or defects evident at birth
- can be due to:
i. genetic factors (i.e. chromosome abnormalities)
ii. environmental agents and factors (i.e. infections, drugs, and radiation = TERATOGENS)

Question 3

Embryo vs. Fetus

Answer 3

Similarities:
- developing young of an animal in a womb

Differences:
i. Embryo
- first 8 weeks of development
- structures are not easily recognizable

ii. Fetus
- development period after embryo stage
- structures are more easily recognizable

Question 4

Embryonic Germ Layers

Answer 4

Week 3

1. Endoderm
   - inside tube (primitive gut)
2. Mesoderm
   - middle
3. Ectoderm
   - outside tube

Opening at both ends of the tube:
1. Mouth (cephalic/head)
2. Anus (caudal/tail)

Question 5

Endoderm

Answer 5

• Most internal germ layer
• forms the lining of the stomach, pharynx, and other internal organs

Question 6

Ectoderm

Answer 6

• Most exterior germ layer
• forms skin, lining of oral cavity, tooth enamel, nervous system, and other external tissues

Question 7

Mesoderm

Answer 7

• Middle germ layer
• forms muscle, skeletal system, circulatory system, dentin, pulp, cementum

Question 8

Cleft lip

Answer 8

Unfused area of the upper lip
- fusion of upper lip should occur around week 6
- Cause: failure to fuse one or both maxillary processes with median nasal process
- usually unilateral
- Appearance: absence of center and adjacent lip
- Nose often mis-shaped on affected side

Question 9

Cleft palate

Answer 9

Unfused areas of a palate
- fusion should occur between week 8-12
- Causes: improper or complete failure to fuse premaxillary area with lateral palatine processes (palatal shelves)

Question 10

Epithelial Rests

Answer 10

Misplaced groups of epithelial cells
- cells from ectoderm germ layer
- found between embryonic processes fusing together
- causes formation of cysts (group of epithelial cells divided and form a sac) - cysts can grow and distort tissues including teeth

Question 11

Odontoma

Answer 11

An anomaly or tumor relating to teeth
- benign
- made up of all or some of the tissues that develop into teeth
- two general types:
i. compound (resembles a tooth)
ii. complex (does not resemble a normal tooth)

Question 12

Nasolabial cyst

Answer 12

A cyst in soft tissue where the upper lip meets the nasal ala

Question 13

Brachial Cleft Cyst

Answer 13

• Congenital epithelial cysts, which arise on the lateral part of the neck
• a failure of the destruction of the second branchial cleft in embryonic development