Blastogenesis, Gastrulation, Notogenesis, Early Embryonic Development

Question 1

During the process of implantation:

a) the development of the blastocyst components starts
b) the first embryonic germ layers appear
c) the structure called morula will appear
d) the allantois will be destroyed

Answer 1

A,b

Question 2

The process of implantation:

a) starts at approximately on 5th or 6th day of embryo development
b) takes approximately 5 days
c) it occurs during the second week of embryonic development

d) the blastocyst components will develop in the extraembryonic structures as well
as in the first embryonic germ layers

Answer 2

A,b,c,d

Question 3

The primary chorionic villus:

a) is a cytotrophoblastic core covered by syncytiotrophoblast
b) does not contain extraembryonic mesoderm yet
c) is formed by 16 compacted blastomeres
d) is formed by cytotrophoblast and oogonia

Answer 3

A,b

Question 4

The secondary chorionic villi:

a) appear early at the 3rd week of embryo development

b) consists of the extraembryonic mesoderm that enters cytotrophoblastic core co-
vered by syncytiotrophoblast

c) cover the whole internal surface of the chorionic sac

d) differentiate into the ectoderm, mesoderm and endoderm to form the embryonic
disc

Answer 4

A,b,c

Question 5

The tertiary chorionic villi:

a) contain no blood capillaries
b) become a basic structure involved in the materno-fetal exchange
c) form the embryonic disc
d) differentiate into the Hensens node

Answer 5

B

Question 6

The decidua:

a) is the endometrium of a gravid uterus
b) contains also oocytes and sperms
c) usually the spermatogonia are present
d) is the myometrium during a twin pregnancy

Answer 6

A

Question 7

During the gastrulation, the embryoblast divides into:

a) two blastocysts
b) a thicker sheet of epiblast (first stage of ectoderm)
c) a thinner sheet of hypoblast (future entoderm)
d) two morulas

Answer 7

B,c

Question 8

The embryonic disc:

a) consists of the epiblast of the bottom of amniotic sac and the hypoblast of the
yolk sac roof

b) it is a bilaminar disc
c) consists of the first two embryonic germ layers – ectoderm and entoderm
d) it is formed by 16 compacted blastomeres

Answer 8

A,b,c

Question 9

The embryonic disc:

a) consists of the bottom of amniotic sac and the yolk sac roof
b) appears at the end of the third day of the development of the human embryo
c) consists of chorion and amnion
d) it is formed by 4 blastomeres

Answer 9

A

Question 10

The chorion consists of:

a) primary mesoderm
b) cytotrophoblast
c) syncytiotrophoblast
d) amnion

Answer 10

A,b,c

Question 11

The amnion consists of:

a) chorion
b) primary mesoderm
c) amniotic ectoderm
d) syncytiotrophoblast

Answer 11

B,c

Question 12

The primary mesoderm:

a) contributes to chorion
b) contributes to amnion
c) appears at the 5th day of development
d) appears as the first germ layer

Answer 12

A,b

Question 13

The gastrula:

a) appears at the end of the second month of development
b) it is represented by first two germ layers forming the embryonic disc
c) appears as a next stage after the morula stage
d) it has fully a functioning placenta

Answer 13

B

Question 14

The dorsal ectoderm and ventral entoderm:

a) at first they lie in close contact

b) gradually the ventral entodermal epithelium becomes thickened at two points – anteriorly the thickening is called prechordal plate (future mouth region) and posteriorly the thickenig forms a cloacal plate which extends in a hollow diver- ticle, known as allantois
c) both appear at the second day of development and disappear at the third month

d) both disappear at the day when the mesoderm appears

Answer 14

A,b

Question 15

The primitive streak:

a) it is at first elongated but then subsequently it is circular

b) it is a linear condensation of primitive ectodermal cells in the posterior midline
of the embryonic disc

c) appears at the third week of development

d) it is crucial for the establishment of the first cranio-caudal and right-left axes of
the embryo

Answer 15

B,c,d

Question 16

The primitive node:

a) is formed at the anterior end of the primitive streak
b) it is in fact an accumulation of cells that express many signaling molecules
c) it is also called the Hensen’s node
d) the migrating cells from the node form a notochordal process

Answer 16

A,b,c,d

Question 17

Allantois:

a) is a hollow diverticle
b) projects into the connecting stalk

c) is an evolutionary reminiscence associated with the removal of embryonic waste
products mostly in oviparous animals

d) it has lost its developmental significance in mammals, because the waste pro-
ducts are removed via the placenta

Answer 17

A,b,c,d

Question 18

Allantois:

a) is flat strip, a one layered cellular cord
b) it is a luminized projection into the connecting stalk
c) it is associated with breathing during the fetal period
d) it appears at the second month of development

Answer 18

B

Question 19

The notochord:

a) it is a solid rounded cord of cells
b) it is also called chorda dorsalis
c) it is situated in the midline between ecto- and entoderm

d) it is believed to act as an inducer of the various axial structures (like the neural
plate)

Answer 19

A,b,c,d

Question 20

The notochord:

a) is formed by only mesenchymal components and it is a flat line of cells
b) it appears at the second month of development
c) it is situated in the midline between ecto- and entoderm

d) it is believed to act as an inducer of the various axial structures, like the neural
plate

Answer 20

C,d

Question 21

The stripes of secondary mesoderm situated on either side of the notochordal plate
can be divided into:

a) paraxial (segmental) mesoderm
b) intermediate mesoderm
c) medial plate mesoderm
d) lateral plate mesoderm

Answer 21

A,b,d

Question 22

The somitogenesis:

a) proceeds until there are 4–6 pairs of somites
b) is characterized by the fact that the most caudal somites disappear in humans because they were predetermined to form a tail structure (and some fuse in the coccyx region)

c) the most cranial somites participate in the development of the head chondro-
cranium

d) the somites are the first segmented organs of the body and influence the pattern
of other organs, like skeleton, muscles, vessels and spinal nerves

Answer 22

B,c,d

Question 23

By the end of the third week of human embryonic development:

a) only two layers, the ectoderm and the endoderm, are under normal conditions
present

b) all three primary germ layers have been developed
c) all three germ layers disappear and do not contribute to the future organogenesis
d) they can not derive in any secondary germ tissues, e.g. of the mesenchyme type

Answer 23

B

Question 24

Which of the statements are correct?

a) in general terms the ectoderm will give rise to the epidermis of the skin
b) the ectoderm will give rise to the most of nerve tissue

c) the entoderm will represent a starting point for the lining of the gut and organs
derived from the gut, e.g. the respiratory system lining

d) the mesoderm contributes to the urogenital apparatus and mostly in its mesen- chymal type to the muscles and connective tissue as well as to the blood and vessel lining

Answer 24

A,b,c,d

Question 25

Which statements are correct?

a) in general terms the ectoderm will give rise to the lining of intestine
b) the ectoderm will give rise to the most of blood cells,
c) the entoderm will represent a starting point for the central nervous system
d) the mesoderm contributes to the urogenital apparatus and mostly in its mesen- chymal type to the muscles and connective tissue as well as to the blood and vessel lining

Answer 25

D