Basics Of Embryology 1

Question 1

_______ is a specialized process of cell division that only occurs in the germ line.

What does “germ line” mean?

Answer 1

Meiosis

Sex cells

Question 2

What does mitosis yield?

Answer 2

2 diploid 2N daughter cells.

Question 3

What does meiosis yield?

Answer 3

4 haploid, 1N, offspring

Question 4

In males, how does meiosis occur?

Answer 4

Cell divisions are equal and 4 identical spermatozoa are created

Question 5

In females, how does meiosis work?

Answer 5

The cell divisions are unequal, yielding a single massive haploid locate and 3 small, nonfunctional, haploid polar bodies.

Question 6

Day 0 of development

Answer 6

Fertilization, pronuclear stage

Haploid sperm fuses with the haploid egg

Question 7

When the sperm fuses with the egg, the result is a..

Answer 7

Zygote (diploid)

Question 8

Day 1 of Development

Answer 8

Cleavage, within 1st 24 hours.

2 cell phase

Question 9

Rapid series of mitotic cell divisions

Answer 9

Cleavage

Question 10

Daughter cells within a zygote during cleavage

Answer 10

Blastomeres

Question 11

Day 2 of development

Answer 11

4 cell phase

Question 12

Day 3 of development

Answer 12

8 cell phase, and undergo compaction.

Question 13

What is compaction?

Answer 13

It means the blastomeres become adhered to one another by tight junctions. During Day 3, and the 8 cell stage,

Question 14

Day 4 of development

Answer 14

Embryo consists of 16 to 32 cells, also known as a morula (latin for blueberry lol)

Question 15

What is a morula?

Answer 15

16 to 32 cells in day 4 of embryo development

Question 16

When the blastomeres segregate to the center of the morula during compaction, these centrally placed blastomeres are now called:

Answer 16

Embryoblasts

Question 17

Blastomeres now placed at the periphery of the morula during compaction is called…

Answer 17

Trophoblasts

Question 18

The inner cell mass of the morula gives rise to the

Answer 18

Embryo proper

Question 19

The trophoblast is the primary source of the fetal component of the..

Answer 19

Placenta. Aka the periphery cells

Question 20

What is blastocoel?

Answer 20

A large cavity within the morula

Question 21

When is the blastocyst formed?

Answer 21

Day 5/96 hours

When the inner and peripheral cells are differentiated into a cavity and a singled layered epithelium.

Question 22

When does the morula reach the uterus? What happens then?

Answer 22

Between 3 and 4 days of development.

Implantation occurs very soon after, when the blastocyst adheres itself to the uterine lining.

Question 23

What is decidual reaction?

Answer 23

When the cells of the endometrial stroma respond to the progesterone secreted by the corpus luteum and differentiate into metabolically active, secretory cells called DECIDUAL CELLS

Question 24

When do cells of the embryoblast begin to differentiate into two epithelial layers?

Answer 24

Even before implantation occurs

Question 25

By day 8, the embryoblast consists of a distinct external later of columnar cells called the _________ and an internal layer of cuboidal cells called the __________

Answer 25

Epiblast

Hypoblast or primitive endoderm

Question 26

The resulting two-layered embryoblast is called the:

Answer 26

Bilaminar embryonic disc or bilaminar blastoderm

Question 27

First new cavity to form during the 2nd week that appears on day 8 as fluid begins to collect between cells of the epiblast and trophoblast

Answer 27

Amniotic cavity

Question 28

When is the embryo completely implanted into the uterine endometrium?

Answer 28

By nine days.

Question 29

The migrating hypoblast cells merge to form a second cavity called the…

Answer 29

Primary yolk sac

Question 30

When is the extraembryonic mesoderm formed?

Answer 30

In the middle of the second week/days 10 to 11

Question 31

One days 12 to 13, what forms within the extraembryonic mesoderm?

Answer 31

The chorion.

Question 32

On day 13 what happens to the primary yolk sac?

Answer 32

It breaks up and is reduced to a collection of vesicles at the abembryonic end of the chorionic cavity

Question 33

By the end of the 2nd week, what happens between the definitive yolk sac and the primary yolk sac?

Answer 33

The bilaminar embryonic disc with its dorsal amnion and its ventral yolk sac is suspended within the chorionic cavity by a think connecting stalk

Question 34

With splitting of the extraembryonic mesoderm into two layers, the amnion, yolk sac, and chorion all become 2 layer structures.

Chorion and amnion consist of ________ and _________

Yolk sac consists of _________ and __________

Answer 34

Ectoderm and mesoderm

Endoderm and mesoderm

Question 35

Extraembryonic mesoderm forming the outer layer of the yolk sac is a major site of….

Answer 35

Hematopoiesis (blood formation)

Question 36

What is meckels diverticulum?

Answer 36

When the yolk sac fails to disappear before birth and persists in the form of a digestive tract anomaly