Embryology

Question 1

The first stage in the development of a fetus

Answer 1

fertilisation the process by which the male sperm and female egg join together.

Question 2

Approximately _______ hours after fertilizations, the fertilized oocyte (egg) splits into two cells of equal size; called _________.

Answer 2

thirty; blastomeres

Question 3

After three more divisions, there are 16 cells. At this point, the group of cells is referred to as the ______.

Answer 3

morula

Question 4

Within the first week, the cells of the morula reorganize to form a cavity, known as the ______.

Answer 4

blastocyst cavity (blastocoel).

Question 5

the blastocyst is comprised of two different cell types:

Answer 5

Outer cell mass (trophoblast) Inner cell mass (embryoblast)

Question 6

contacts with the endometrium of the uterus to facilitate implantation and the formation of the placenta

Answer 6

Outer cell mass (trophoblast)

Question 7

responsible for the formation of the embryo itself

Answer 7

Inner cell mass (embryoblast)

Question 8

The trophoblast divides into the _______ and ______

Answer 8

syncytiotrophoblast and cytotrophoblast.

Question 9

The embryoblast divides into the ______ and ______.

Answer 9

epiblast and hypoblast , forming a two-layered structure; the bilaminar disk.

Question 10

The amniotic cavity forms within

Answer 10

the epiblast

Question 11

Initial Cellular Divisions

Answer 11

Question 12

After the initial rounds of cellular divisions, the embryo must implant into the __________

Answer 12

endometrium of the uterus

Question 13

During this process, the syncytiotrophoblast becomes continuous with the uterus – such that maternal blood vessels (known as sinusoids) invade the spaces within the syncytiotrophoblast (known as lacunae).

Answer 13

Implantation

Question 14

In___________, implantation of the embryo occurs in the lower uterine segment (instead of in the normal position of the upper posterior uterine wall).

Answer 14

placenta praevia

Question 15

A low-lying placenta is more susceptible to

Answer 15

haemorrhage

Question 16

In the 3rd week of embryonic development, the cells of the bilaminar disk (epiblast and hypoblast) undergo a highly specialised process called

Answer 16

gastrulation

Question 17

a process of cellular rearrangement which involves migration, invagination and differentiation of the epiblast.

Answer 17

Gastrulation

Question 18

a groove in the midline of the epiblast which appears during the third week

Answer 18

The primitive streak

Question 19

Within the primitive streak lies a ________ at the cranial end, and within that lies the ________ .

Answer 19

primitive node; primitive pit

Question 20

Cells of the epiblast layer break off and migrate toward the __________

Answer 20

primitive pit

Question 21

three germ cell layers:

Answer 21

Endoderm

Mesoderm

Ectoderm

Question 22

formed by epiblast cells that migrate through the primitive pit and displace the hypoblast cells.

Answer 22

Endoderm

Question 23

formed by epiblast cells that migrate through the primitive pit and lie between the epiblast layer and the newly created endoderm.

Answer 23

Mesoderm

Question 24

formed by the epiblast cells that remain in position

Answer 24

Ectoderm

Question 26

Formation of the three primary germ layers

Answer 26

Question 27

Structures derived from the endoderm

Answer 27

• Epithelial lining of digestive and respiratory tracts
• Lining of urethra, bladder and reproductive System
• Liver and pancreas

Question 28

Structures derived from the mesoderm

Answer 28

• Notochord
• Musculosketal system
• Muscular layer of stomach, intestine etc
• Circulatory system

Question 29

Structures derived from the ectoderm

Answer 29

• Epidermis of skin
• Cornea and lens of eye
• Nervous system