embryology

Question 1

Haploid egg + Haploid sperm =

Answer 1

single diploid cell

Question 2

what results from rapid cell replication?

Answer 2

ball of totipotent cells = 8 cells –> 16 pluripotent stem cells

Question 3

what happens to pluripotent cells?

Answer 3

differentiate into different cells types - some remain as stem cells

Question 4

what is a blastocyst?

Answer 4

hollow ball of cells consisting of:

• outer layer trophoblast
• inner cell mass

Question 5

which layer of the blastocyst give rise to the placenta? when?

Answer 5

the outer layer trophoblast at day 5

Question 6

which layer of the blastocyst develops into the embryo?

Answer 6

inner cell mass. day 5

Question 7

what is a decidua?

Answer 7

uterine lining during pregnancy which forms the maternal part of the placenta..

endometrial glands enlarge and the inner cell mass is orientated to the uterine endometrium.

day 6

Question 8

The cell mass initially differentiates into which layers?

Answer 8

• hypoblast / primitive endometrium

- epiblast /primitive ectoderm

Question 9

what is the bilaminar embryonic disc?

Answer 9

The hypoblast and epiblast cells

Question 10

what is an amnion?

Answer 10

small cavity in the bilaminar disc.

Question 11

what is the exocoelomic membrane?

Answer 11

membrane around the inner surface of the blastocyst

Question 12

what do the cells in the yolk sac develop into?

Answer 12

gonads + part of GI tract

Question 13

what is gastrulation?

Answer 13

phase early in the embryonic development, during which the single-layered blastocyst is reorganized into a multilayered (3) structure.
The bilaminar develops into a trilaminar disc

Question 14

what are the primary germ layers in the trilaminar disc?

Answer 14

• ectoderm
• mesoderm
• endoderm

Question 15

what do each germ layer give rise to?

Answer 15

1) Ectoderm give rise to skin + nervous system
2) Mesoderm muscles + bone
3) Endoderm epithelial lining of GI tract and, any organs

Question 16

what is the primitive streak?

Answer 16

groove on dorsal surface of epiblast that extends from posterior (tail region) to anterior (node) region of bilaminar disk.

Question 17

After the formation of the primitive streak, the epiblast cells migrate inwards below the primitive streak.

1) which layer do some of the cells displace?
2) what layer of the trilaminar disc is formed?

Answer 17

1) hypoblast

2) mesoderm

Question 18

what is the notochordal process?

Answer 18

a hollow tube which develps into a solid notochord layer at day 16