Embryology

Question 1

What is a malformation?

Answer 1

Primary structural defect from localized error in morphogenesis; abnormal formation of tissue or organ.
*most common defect

Question 2

What is dysplasia?

Answer 2

Abnormal organization of cells into tissues (ex. cleft lip)

Question 3

What is deformation?

Answer 3

Alteration in shape or structure of a structure or organ that has differentiated normally (ex. clubbed foot)

Question 4

What is a disruption?

Answer 4

Structural defect resulting from destruction of structure that had formed normally before the insult

Question 5

What generally occurs in week 1?

Answer 5

1. embryo has been fertilized
2. divides and travels through fallopian tube
3. cleaves and forms morula
4. implantation in wall of uterus

Question 6

Which part of the embryo works its way into the wall of the uterus?

Answer 6

Trophoblast

Question 7

What generally occurs in week 2?

Answer 7

“the week of 2’s”

1. trophoblast -> 2 layers (syncytiotrophoblast, cytotrophoblast)
2. embryoblast -> 2 layers (epiblast, hypoblast)
3. two cavities (amniotic, yolk sac)

Question 8

What is the first sign of gastrulation?

Answer 8

Primitive streak

Question 9

What occurs in week 3, day 15/16?

Answer 9

formation of the trilaminar disc (gastrulation – differentiate ectoderm/endoderm/mesoderm)

Question 10

What occurs in week 3, day 16?

Answer 10

migration of cells from the epiblast (primitive streak)

• mesenchymal cells come down and populate space between epiblast and hypoblast (replace cells in hypoblast to form three layers)
• development of left/right/cranial/caudal orientation

Question 11

What occurs in week 3, day 18?

Answer 11

formation of the notochord

• ectoderm begins to form neural groove
• neurulation - neural fold and tube from neural crest

Question 12

What occurs in week 3, day 20-21?

Answer 12

zipping up of the neural tube

Question 13

What occurs in week 4, day 24-28?

Answer 13

Neural tube closes and neural crest cells separate from tube

-aided by folate supplementation in pregnant women

Question 14

What occurs in week 3, day 18-19?

Answer 14

Formation of mesoderm

Question 15

What occurs in week 3, day 21?

Answer 15

Lateral plate of mesoderm splits into parietal and visceral mesoderm of body cavities.

Paraxial mesoderm will form somites.

Question 16

What occurs in week 3-4, days 17-28?

Answer 16

Head and tail folding

Question 17

What occurs at week 4, 25-28 days?

Answer 17

Somite formation from paraxial mesoderm; anterior and posterior begin to close