embryology

Question 1

Once a haploid sperm fuses with the haploid

egg the egg is then called a

Answer 1

zygote (diploid)

Question 2

Day 0

is ?

Answer 2

Fertilization

Question 3

Day 1 (24 hours)

Answer 3

Cleavage

Question 4

the zygote initiates a rapid
series of mitotic cell divisions
called \_\_\_\_\_The cells
increase in number but the
zygote does not increase in
size. These daughter cells are
called \_\_\_\_\_\_\_\_\_.

Answer 4

cleavage.

Blastomeres

Question 5

Day 3

Answer 5

8 CELLS/

coMPACTION

Question 6

day 4

Answer 6

morula

Question 7

compaction :

inside______
outside______

Answer 7

embryoblast

trophoblast

Question 8

trophoblast gives rise to the_____

Answer 8

placenta

Question 9

4 days

morula has ______ cells and a large cavity called_____

Answer 9

30

blastocyst cavity

Question 10

day 5

Answer 10

blastocyst

Question 11

implantation happens between __to___ days

Answer 11

3-4

Question 12

implantaton:
progesterone secreted by the corpus luteum by differentiating into
metabolically active, secretory cells called _______This response
is called the decidual reaction

Answer 12

decidual cells.

Question 13

By day eight, the embryoblast
consists of a distinct external (or upper) layer of columnar cells, called
the ______ and an internal (or lower) layer of cuboidal cells, called the

__________(see Figs. 2-1, 2-2).

Answer 13

epiblast,hypoblast, or primitive endoderm

Question 14

The resulting two-layered
embryoblast is called the
bilaminar embryonic disc, or
bilaminar blastoderm.

(i.e., ____ is dorsal,
______ is ventral)

Answer 14

epiblast

hypoblast

Question 15

The first new cavity to form
during the second week—the
amniotic cavity—appears on
day eight as fluid begins to
collect between cells of the
\_\_\_\_\_\_\_\_and \_\_\_\_\_\_\_(see Fig. 2-2).

Answer 15

epiblast and overlying

trophoblast

Question 16

by 9 days cells from the ______ have begun to migrate to for the heuser’s membrane

Answer 16

hypoblast

Question 17

the amnion and the chorion
are considered to consist of
extraembryonic \_\_\_\_\_\_\_\_and \_\_\_\_\_\_\_ whereas the yolk
sac is considered to consist of
extraembryonic \_\_\_\_\_\_\_\_and \_\_\_\_\_\_\_\_\_\_\_\_

Answer 17

ectoderm and
mesoderm,

endoderm
and mesoderm

Question 18

Extraembryonic mesoderm
forming the outer layer of the
yolk sac is a major site of:;

Answer 18

hematopoiesis (blood

formation).

Question 19

First major event of the third week

Answer 19

gastrulation

Question 20

primitive
streak, in the epiblast near the
caudal end of the________

Answer 20

bilaminar

embryonic disc

Question 21

The blastocyst contains which 2 parts?

Answer 21

• the inner cell mass (ICM) and the trophoblast

Question 22

Cells in the ICM differentiate into…?

•

Answer 22

1. Epiblast which gives rise to the embryo proper (dorsal - back)
   • 2. Hypoblast which gives rise to the primary (extraembryonic)
   endoderm that forms the yolk sac (ventral - belly)

Question 23

What is the primitive streak?

•

Answer 23

first marker of the craniocaudal axis. It occurs on the dorsal side of
the epiblast and near the caudal end of the epiblast. The cranial end
of the streak proliferates to become the primitive node and results
from proliferation and migration of cells

Question 24

How do we turn the 2-layer disc into a 3
layer disc?
•

Answer 24

Through gastrulation. There is a depression in the primitive streak
called the primitive groove, and it is the site along which the cells
migrate through the epiblast. The first cells to migrate (ingress)
through the epiblast form the endoderm (and displace hypoblast
cells). Later cells form the mesoderm, and non-ingressing cells form
the ectoderm. 2 populations of cells that migrate through the streak
generate the 3 layer disc from 2 layer disc.

Question 25

What is Gastrulation?

•

Answer 25

process by which the three germ layers are formed through cell
migration

Question 26

what are the 3 ways in which cells can
migrate through the epiblast and why is that important?
•

Answer 26

1. through the node.
2. near the node
3. away from the node.
   • It is important because they create three different cell fates. where
   you migrate through the primitive streak helps to determine your
   fate.

Question 27

How is the neural tube formed?

•

Answer 27

Dorsal ectoderm becomes the neural plate. Lateral edges become
elevated to form neural folds and mid-region becomes depressed and
form the neural groove. Neural fold moves toward each other and
fuse to become the neural tube. Neural tube than detaches from the
overlying ectoderm

Question 28

What does the nonneural ectoderm
becomes?
•

Answer 28

The skin

Question 29

What does the neural ectoderm becomes?

•

Answer 29

• The brain and spinal cord (Central nervous system).

Question 30

What germ layer does the notochord

derive from?

Answer 30

• Mesoderm

Question 31

What is neurulation?

Answer 31

• Formation of the neural tube.

Question 32

How do cells fuse during neurulation?

•

Answer 32

• Cells in the middle of the neural folds fuse first and zippers both
anteriorly and posteriorly at the same time

Question 33

What are Cranial and caudal neuropores?

•

Answer 33

• transient openings at either end of the neural tube after zippering of
the neural folds occur.

Question 34

How do birth defects or neural tube defects occur?
How should women avoid neural tube defects?
•

Answer 34

• When the neuropores do not close correctly

* consume more folic acid.

Question 35

what are the functions of the notochord?

Answer 35

• transient structure that defines the body axis
• provides rigidity to the embryo
• functions as a signaling center to, at least, induce neural fates
such as which neural cells become dorsal or ventral.
• precursor for the axial skeleton.

Question 36

Which germ layer forms the neural crest?

Answer 36

• ectoderm

Question 37

What are neural crest cells?
• migratory cells that are ectoderm-derived and migrate
throughout the body to give rise to a diverse number of cell fates

Answer 37

What are neural crest cells?
• migratory cells that are ectoderm-derived and migrate
throughout the body to give rise to a diverse number of cell fates

Question 38

what are the 4 regions of mesoderm?

•

Answer 38

• 1. axial (chordamesoderm) - gives rise to the notochord
2. paraxial mesoderm - give rise to somites, adjacent to the
neural tube.
3. intermediate mesoderm - gives rise to kidney/gonads
4. lateral plate mesoderm - gives rise to the lining of the organ cavities

Question 39

What are the derivatives of endoderm?

Answer 39

• gives rise to the GI tract, epithelial lining of lung buds and
trachea, liver, gall bladder, and pancreas