EMBRYOLOGY

Question 1

What occurs on days 1-3 during embryological development?

Answer 1

The zygote moves to the fallopian tube, and cleavage results in marula

Question 2

What is cleavage?

Answer 2

Where cells multiply/divide into numerous smaller nucleated cells

Question 3

What is marula?

Answer 3

a solid ball/clump of undifferential cells

Question 4

How do twins occur regarding eggs?

Answer 4

When one fertilized egg splits into two this forms monozygotic twins aka identical. When two eggs are fertilized at the same time, this forms dizygotic twins aka fraternal.

Question 5

What occurs on days 4-6 during embryological development?

Answer 5

Cleavage will continue but the morula becomes hollow. The hollow space is known as the blastula. A cluster of cells will still remain.

Question 6

What is the cluster of cells referred to as in the morula?

Answer 6

The inner cell mass

Question 7

What is the outer cell lining referred to as in the morula?

Answer 7

Trophoblast

Question 8

What important event occurs on day 6 of embryological development?

Answer 8

Implantation

Question 9

What occurs during implantation?

Answer 9

The morula will move to the uterus. Once it reaches the uterus it is referred to as a blastocyst. Implantation occurs when the blastocyst burrows into the mucosal uterine lining aka the endometrium

Question 10

What is the Decidua?

Answer 10

The decidua is the specialized layer of endometrium that forms the base of the placental bed

Question 11

What is the Decidua Basalis?

Answer 11

The portion of decidua where the placenta is to be formed. Endometrium deep from blastula.

Question 12

What is the Decidua Capsilaris?

Answer 12

The part of the decidua that separates the embryo from the uterine lumen. Endometrium surface from blastula.

Question 13

What is the Decidua Parietalis?

Answer 13

The part lining the rest of the uterus cavity. Endometrium absent from blastula.

Question 14

What is the difference between the Trophoblast, Blastocyst cavity, and Embryoblast?

Answer 14

All are components of a blastocyst. The trophoblast is the outer lining, the embryoblast is the inner cell mass, and the blastocyst cavity is the empty area left.

Question 15

On days 6-12, why do the trophoblasts become cytotrophoblasts?

Answer 15

To penetrate maternal spiral arteries and route the blood flow through the placenta for the growing embryo to use.

Question 16

On days 6-12, why does the endometrium become a syncytiotrophoblast?

Answer 16

To cover the entire surface of villous trees and are in direct contact with maternal blood. They are a continuous, specialized layer of epithelial cells.

Question 17

On days 6-12, why does the inner cell mass become an embryonic disc?

Answer 17

For the embryo to begin differentiating. It lies between the hypoblast layer and the amnion. It is the part of the inner cell mass of a blastocyst from which the embryo of a placental mammal develops

Question 18

What does the embryonic disc consist of? (hint: 3 layers)

Answer 18

-Endoderm (inner layer)
-Mesoderm (middle layer)
-Ectoderm (outer layer)