Question 1

________ Ectodermal depression in the neck&#10;A)Limb bud&#10;B)Neuropore&#10;C)Septum transversum&#10;D)Cervical sinus&#10;E)Stomodeum

Accepted Answer

The cervical sinus is a depression in the surface ectoderm on each side of the future neck.It forms when the second pharyngeal arch overgrows the third and fourth arches.The second and third arches come to lie at the bottom of a pit-the cervical sinus.It is visible externally only during the fifth week.

Question 2

______ Oropharyngeal membrane&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The oropharyngeal membrane develops during the third week as the prechordal plate fuses with the overlying embryonic ectoderm.This membrane ruptures during the fourth week.

Question 3

________ Forms from the paraxial mesoderm&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The somites form by differentiation and division of longitudinal columns of paraxial mesoderm into cubical segments.The somites give rise to most of the axial skeleton,the associated musculature,and the dermis of the skin.

Question 4

______ Gives rise to a major part of the diaphragm&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The septum transversum is the first recognizable part of the developing diaphragm.It appears cranially at the end of the third week,when the pericardial coelom forms.The septum transversum later forms the central tendon of the diaphragm.

Question 5

______ Separates the amniotic cavity from the hindgut&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The cloacal membrane separates the amniotic cavity from the cloacal region of the hindgut.This membrane consists of fused layers of embryonic ectoderm and endoderm.It is later divided into anal and urogenital membranes during the seventh week;these membranes soon rupture.

Question 6

________ Closes during the fourth week&#10;A)Limb bud&#10;B)Neuropore&#10;C)Septum transversum&#10;D)Cervical sinus&#10;E)Stomodeum

Accepted Answer

The neuropores close during the fourth week.The rostral neuropore closes on day 25 or 26,and the caudal neuropore closes about 2 days later.Defects of closure of the neuropores give rise to congenital anomalies of the central nervous system (e.g. ,spina bifida).

Question 7

______ Produces embryonic mesoderm&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The primitive streak appears during the early part of the third week and produces mesoderm rapidly until the end of the fourth week.Thereafter,mesoderm production from this source slows down.

Question 8

________ Hyoid arch&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The second or hyoid pharyngeal arch is recognizable early in the fourth week.As its name implies,this arch gives rise to part of the hyoid bone.Mesenchyme in this arch also gives rise to the muscles of facial expression and to various skeletal structures.

Question 9

______ Part of the embryonic coelom&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The septum transversum is a mass of mesoderm that is first recognizable cranial to the pericardial coelom.After folding,it lies caudal to the heart and pericardial coelom.The septum transversum gives rise to the central tendon of the definitive diaphragm.

Question 10

______ Separates the amniotic cavity from the foregut&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The oropharyngeal membrane separates the amniotic cavity from the foregut.Amniotic fluid may enter the primordial mouth or stomodeum,but it cannot pass into the primordial pharynx until the oropharyngeal membrane ruptures.

Question 11

______ Site of blood formation in the early embryo&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The answer of   ______ Site of blood formation...

Question 12

______ Amnion&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The answer of   ______ Amnion&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E...

Question 13

________ Optic groove in neural fold&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The answer of     ________ Optic groove...

Question 14

________ Outgrowth of the ventrolateral body wall&#10;A)Limb bud&#10;B)Neuropore&#10;C)Septum transversum&#10;D)Cervical sinus&#10;E)Stomodeum

Accepted Answer

The answer of ________ Outgrowth of the ventrolateral body wall&#10;A)Limb...

Question 15

______ Second pharyngeal arch&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The answer of   ______ Second pharyngeal arch&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E...

Question 16

________ Neuropore&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The answer of     ________ Neuropore&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E...

Question 17

________ Gives rise to the mandible&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The answer of     ________ Gives rise...

Question 18

______ Cloaca&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The answer of   ______ Cloaca&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E...

Question 19

________ Forms the major part of the diaphragm&#10;A)Limb bud&#10;B)Neuropore&#10;C)Septum transversum&#10;D)Cervical sinus&#10;E)Stomodeum

Accepted Answer

The answer of ________ Forms the major part of the...

Question 20

________ Primordial mouth&#10;A)Limb bud&#10;B)Neuropore&#10;C)Septum transversum&#10;D)Cervical sinus&#10;E)Stomodeum

Accepted Answer

The answer of ________ Primordial mouth&#10;A)Limb bud&#10;B)Neuropore&#10;C)Septum transversum&#10;D)Cervical sinus&#10;E)Stomodeum...

Question 21

______ Gives rise to the upper jaw&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The answer of   ______ Gives rise to the...

Question 22

______ Stomodeum&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The answer of   ______ Stomodeum&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E...

Question 23

______ Defect in its formation results in a severe type of spina bifida&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The answer of   ______ Defect in its formation...

Question 24

______ Will form the lower jaw&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

The answer of   ______ Will form the lower...

Deck 4: Organogenetic Period: the Fourth to Eighth Weeks