30.01.25

Question 1

What is cleavage in early embryo development?

Answer 1

Rapid cell division without growth from zygote to 8-cell stage. Embryo remains same size; cells called blastomeres.

Question 2

What is the significance of a blastomere?

Answer 2

Totipotent cell from 2-8-cell stage; can form twins if split; removal doesn’t affect development.

Question 3

What happens during compaction?

Answer 3

Blastomeres increase contact to form morula using E-cadherin; first cell differentiation begins.

Question 4

What does Cdx2 do in the embryo?

Answer 4

Drives formation of trophectoderm. Without it, trophectoderm doesn’t form → blastocyst doesn’t form.

Question 5

What is the function of the trophectoderm?

Answer 5

Forms the first epithelium, creates blastocoel via Na+ pumping, supports implantation and placenta development.

Question 6

How does a blastocyst form?

Answer 6

Na+ pumped into morula draws water in → blastocoel cavity forms. Trophectoderm cells polarize along apical-basal axis.

Question 7

What is the difference between mural and polar trophectoderm?

Answer 7

Mural lines the blastocoel; polar contacts the inner cell mass (epiblast).

Question 8

What are the two types of primitive endoderm derivatives?

Answer 8

Parietal (makes Reichert’s membrane); Visceral (nutrients + signals for epiblast patterning).

Question 9

What is the role of the anterior visceral endoderm (AVE)?

Answer 9

Moves to the future anterior and patterns the anterior-posterior axis of the embryo.

Question 10

What occurs during gastrulation?

Answer 10

Formation of the 3 germ layers (ectoderm, mesoderm, endoderm); reorganization and cell movement prepare for organ development.

Question 11

What condition is associated with gastrulation defects?

Answer 11

Caudal dysgenesis (sirenomelia) in humans; similar to brachyury mutations in mice.