Embryology

1.

1 point

Where is the germ disc?

suspended between the amniotic cavity and the yolk sac

connected to the chorion by the connecting stalk

engulfed by the amnion

inside the mother

2.

1 point

What statement best describes the relationship between MyoD and Myf-5?

They are probably not functionally related

If either factor is deactivated in a normal individual, myogenesis will be arrested

They are redundant, parallel components in the myogenic pathway

They are both required for myogenesis

3.

1 point

Which is not true concerning somites?

they were once epiblast cells that ingressed through the primitive streak

they are mesodermal

skeletal muscle can be traced back to them

they were once epiblast cells that failed to ingress through the primitive streak

4.

1 point

One reason that many sperm are required for fertilization is that

polyspermy is desirable

the cortical reaction will kill off all undesirable sperm

almost all of the sperm reach the egg

the zona pellucida must undergo many reactions before a single sperm can penetrate it

5.

1 point

The space in which the fetus will develop is the

amnion

chorion

blastocoel

amniotic cavity

6.

1 point

The primitive streak regresses prematurely in a developing embryo. Which medical condition would the developing fetus most likely present?

spina bifida

sirenomelia

sacrococcygeal teratoma

caudal dysgenesis

7.

1 point

The primitive streak fails to regress completely in an embryo. Which medical emergency should you be most concerned about in the developing fetus?

brain ischemia

anencephaly

spina bifida

myocardial infarction

8.

1 point

The first major step in myogenesis is

the specification of a mesenchyme into a somite

the determination of a somite into a myoblast

the differentiation of a myoblast into a muscle fiber

the fusion of multiple myoblasts into a myocyte

9.

1 point

Which of the following is true concerning the tissue immediately exterior to the yolk sac and amnion prior to the lacunar stage?

it consists of many nuclei in a common cytoplasm

it differentiates from the extraembryonic endoderm

it is derived from the trophoblast

it contains many fluid-filled cavities

10.

1 point

What is the primary purpose of the primitive streak?

to establish three germ layers

to establish bilateral symmetry

to form the spinal cord

to separate embryonic and extraembryonic tissues

11.

1 point

An embryologist decides to somehow tag all epiblast cells that invaginate through the primitive streak with a short-lived radioisotope. Where will she not likely be able to detect significant amounts of radioactivity in the embryo?

mesenchyme

ectoderm

Hensen's node

endoderm

12.

1 point

An embryologist decides to tag epiblasts that ingress through the primitive node with a long-lived radioisotope. Where will he find radioactivity in the adult specimen, assuming it survives the procedure?

in the nucleus pulposus

along the alimentary canal

in the spinal cord

throughout the entire body

13.

1 point

Cleavages

retain the maternal and paternal pronuclei

are early mitoses in the developing embyro

are reactions that serve to break down the zona pellucida

only occur after the morula is formed

14.

1 point

Somite formation begins

before gastrulation

in the hypoblast

at the cranial end

at the caudal end

15.

1 point

During first cleavage

the cell cycle is arrested in S phase

the paternal and maternal genomes intermix when the chromatid pairs attach to the spindle

the paternal and maternal pronuclei fuse

a centrosome is derived from the fertilizing sperm cell

16.

1 point

Compaction is an important watershed moment marking

the fusion of maternal and paternal pronuclei

the formation of embryoblasts and trophoblasts

the development of all embryonic and extraembryonic tissues

the removal of the zona pellucida

17.

1 point

Where do somites form?

inside the neural tube

lateral mesoderm

paraxial mesoderm

paraxial endoderm

18.

1 point

The ventral aspect of an adult's legs are mostly covered by

thoracic dermatomes

lumbar dermatomes

caudal dermatomes

sacral dermatomes

19.

1 point

The secondary yolk sac

is attached to the cytotrophoblast by the connecting stalk

has ejected the exocoelemic cyst

is attached to the splachnic extraembryonic mesoderm by the connecting stalk

has not yet ejected the exocolemic cyst

20.

1 point

The chief function of the syncytiotrophoblast is to

tongue-tie medical students

establish an interface between maternal blood and embryonic extracellular fluid

defend the embryo from the mother's immune system

serve as a reservoir for unneeded and expelled trophoblastic nuclei

21.

1 point

Hatching normally occurs

in the uterus, before compaction

in the uterus, after compaction

approximately three mitotic events into development

when the mother's water breaks

22.

1 point

Due to a rare mutation, the epithelial cells of a woman's uterus have deformed proteins. Which stage of pregnancy would this likely have the greatest effect on?

fertilization

hatching

implantation

differentiation

23.

1 point

The endoderm is formed by

epiblasts that ingress through the primitive node

epiblasts that ingress through the primitive ridge

epiblasts that ingress through the early primitive streak

hypoblasts that are pushed into the yolk sac

24.

1 point

The thoracic cavity is ultimately formed by

coeloms that form in the notochordal canal

apoptosis of mesodermal cells

the splanchnopleuric mesoderm

lacunae that form in the lateral mesoderm

25.

1 point

Eight days after a normal fertilization, an embryo implants at the site where it was fertilized. This will result in

a malformed amnion

a normal pregnancy

delayed gastrulation

a serious complication and potential medical emergency

26.

1 point

Which of the following pairs of structures are derived from the same primary germ cell layer?

dermis and epidermis

brain and fingernail

kidneys and urinary bladder

alveoli and blood vessels