Chapter 02 Formation of Bilaminar Embryonic Disc and Chorionic Sac

Chapter 02  Formation of Bilaminar Embryonic Disc and Chorionic Sac

Complete Chapter Questions And Answers
 

Sample Questions

MULTIPLE CHOICE

Directions: Each group of questions below consists of a numbered list of descriptive words or phrases accompanied by a diagram with certain parts indicated by letters or by a list of lettered headings. For each numbered word or phrase, select the lettered part or heading that matches it correctly and then insert the letter in the space to the right of the appropriate number. Sometimes more than one numbered word or phrase may be correctly matched to the same lettered part or heading.

1.
________ Extraembryonic coelom
a.
A
b.
B
c.
C
d.
D
e.
E

ANS: E
The extraembryonic coelom, part of which is indicated in the diagram, consists of isolated spaces in the extraembryonic mesoderm. Later, these spaces coalesce to form a single, large cavity.

2.
________ Cytotrophoblast
a.
A
b.
B
c.
C
d.
D
e.
E

ANS: D
The cytotrophoblast is the inner layer of the trophoblast. It gives rise to (1) the outer layer of trophoblast (syncytiotrophoblast), (2) amnioblasts (cells that form the amnion), and (3) part of the extraembryonic mesoderm. The cytotrophoblast, as the prefix cyto- implies, is a cellular layer.

3.
________ Lacunar network
a.
A
b.
B
c.
C
d.
D
e.
E

ANS: A
The lacunar networks form by coalescence of lacunae in the syncytiotrophoblast. As the maternal sinusoids are eroded, blood seeps into these networks. Nutrients in the embryotroph diffuse through the two layers of trophoblast and pass to the embryo by way of the extraembryonic coelom.

4.
________ Epiblast forms its floor
a.
A
b.
B
c.
C
d.
D
e.
E

ANS: B
The floor of the amniotic cavity is formed by the epiblast. The amnion enclosing the amniotic cavity is attached to the epiblast of the embryonic disc. Initially, some amniotic fluid may be secreted by the amniotic cells, but most of it is derived from the maternal blood.

5. ________ Develops as a localized thickening of hypoblast
a.
Corpus luteum
b.
Zona pellucida
c.
Prechordal plate
d.
Ectopic implantation
e.
Chorionic sac

ANS: C
The prechordal plate indicates the future cranial end of the embryo and the future site of the mouth. It is a circular area of endoderm that is firmly adherent to the overlying embryonic epiblast. It is an important landmark in the early embryo and serves as an organizer of the cranial region of the embryo.