Intro To Embryology

Question 1

What are the stages of the development of the blastocyst?

Answer 1

1. Blastomere (2-cell)
2. Blastomere (4-cell)
3. Blastomere (8-cell)
4. Morula
5. Blastocyst

Question 2

What is the most common site of ectopic implantation?

Answer 2

Ampulla

Question 3

What site of ectopic pregnancies can result in placenta previa?

Answer 3

Lower uterus/cervix

Question 4

What are the layer of the bilaminar disc, and when do they form?

Answer 4

• Epiblast and Hypoblast

- week 2

Question 5

What event establishes the axis of the body?

Answer 5

Formation of the primitive streak

Question 6

What are the layers of the trilaminar disc?

Answer 6

• Ectoderm
• Mesoderm
• Endoderm

Question 7

Which of the germ layers face the yolk sac?

Answer 7

Endoderm

Question 8

What are the three major disruptions that form during gastrulation?

Answer 8

1. Saccrococcegeal teratomas: Remnants of the primitive streak which migrate caudally and form a tumor
2. Caudal dysgenesis: Insufficient Mesoderm results in lack of formation of the lower limbs
3. Situs Inversus: Defects in the formation of the primitive streak leads to defects in establishment of the longitudinal (left-right) axis.

Question 9

Which weeks of development are at the highest risk for the formation of teratomas?

Answer 9

Weeks 3-8

Question 10

Describe the lateral folding of the trilaminar disc.

Answer 10

The embryo folds laterally changing from a flat disc into a cylinder with the ectoderm on the outside,
endoderm forming an inner tube (primitive gut) and mesoderm trapped in between.

Question 11

What structures are formed from an extra fold of ectoderm above the notochord?

Answer 11

• Neural Tube

- Neural Crest

Question 12

What are the fates of NC Cells?

Answer 12

Migrate to form:

• Dorsal root ganglia
• Peripheral nervous system neurons
• Melanocytes
• Langerhans cell (endocrine Cells)
• Conotruncal septum of the heart
• Diverse structures in the head and neck

Question 13

Which body system is the first to function in the developing embryo?

Answer 13

Cardiovascular system

Question 14

Which weeks signify the start of blood flow and electrical activity in the developing heart of the embryo?

Answer 14

Circulating blood -> Week 3

Electrical activity -> week 4

Question 15

What structures are derived from somites?

Answer 15

1. Skeletal muscle
2. Vertebrae and ribs
3. Dermis/ct of the skin

Question 16

Wha?t structures will develop into the future head and neck

Answer 16

Pharyngeal Arches