Question 1

Which of the following tissues is not dependent on the proper functioning of the primitive streak?&#10;A)Ectoderm&#10;B)Notochord&#10;C)Endoderm&#10;D)Mesoderm&#10;E)Amnion

Accepted Answer

The amnion is formed from the extraembryonic mesoderm and is not dependent on the proper functioning of the primitive streak, which primarily gives rise to the three germ layers (ectoderm, mesoderm, endoderm) and the notochord.

Question 2

The principal inductor in primary neural induction is the ____________.&#10;A)Hypoblast&#10;B)Primitive streak&#10;C)Extraembryonic mesoderm&#10;D)Notochordal process&#10;E)Embryonic ectoderm

Accepted Answer

The notochordal process is the principal inductor in primary neural induction, as it secretes signaling molecules that induce overlying ectodermal cells to become neural tissue. The hypoblast, primitive streak, extraembryonic mesoderm, and embryonic ectoderm are not directly involved in primary neural induction.

Question 3

The major organizing center of the gastrulating embryo is the ___________.&#10;A)Inner cell mass&#10;B)Primitive streak&#10;C)Primitive node&#10;D)Oropharyngeal membrane&#10;E)Paraxial mesoderm

Accepted Answer

The primitive node, also known as Hensen's node, is the major organizing center during gastrulation. It plays a crucial role in the formation of the body axis and the development of the notochord and neural tube.

Question 4

In the early embryo,what molecule facilitates the migration of mesenchymal cells between the ectoderm and the endoderm?&#10;A)Chondroitin sulfate&#10;B)Hyaluronic acid&#10;C)ZP3&#10;D)Interleukin-2&#10;E)Oct-3

Accepted Answer

Hyaluronic acid is known to facilitate cell migration during development, particularly in the migration of mesenchymal cells between the ectoderm and the endoderm. This process is important for proper development of various organs and structures, including the heart and lungs.

Question 5

Induction of the central nervous system is brought about by the action of the ___________ on the overlying ectoderm.&#10;A)Hypoblast&#10;B)Chordamesoderm (notochord)&#10;C)Primitive streak&#10;D)Embryonic endoderm&#10;E)Body stalk

Accepted Answer

The notochord (chordamesoderm) is responsible for inducing the central nervous system in the overlying ectoderm during embryonic development.

Question 6

Which cell adhesion molecule(s)rely(ies)heavily on Ca++ for its function?&#10;A)N-CAM&#10;B)E-cadherin&#10;C)Integrin&#10;D)All of the above&#10;E)None of the above

Accepted Answer

E-cadherin relies heavily on calcium ions (Ca++) for its adhesive function, as Ca++ ions are crucial for maintaining its structure and function in cell-cell adhesion.

Question 7

Precursor cells of which of the following embryonic tissues pass through the primitive streak?&#10;A)Cytotrophoblast&#10;B)Neural crest&#10;C)Yolk sac endoderm&#10;D)Amniotic ectoderm&#10;E)None of the above

Accepted Answer

The precursor cells of cytotrophoblast, neural crest, yolk sac endoderm, and amniotic ectoderm do not pass through the primitive streak. The primitive streak is primarily involved in the formation of mesoderm and endoderm of the embryo, not these specific tissues directly.

Question 8

Precursor cells of which of the following embryonic tissues pass through the primitive streak?&#10;A)Cytotrophoblast&#10;B)Syncytiotrophoblast&#10;C)Yolk sac endoderm&#10;D)Amniotic ectoderm&#10;E)None of the above

Accepted Answer

The primitive streak is a structure that forms in the blastula during the early stages of embryonic development in birds and mammals. It is involved in the formation of the three germ layers: ectoderm, mesoderm, and endoderm. However, the options given (A: Cytotrophoblast, B: Syncytiotrophoblast, C: Yolk sac endoderm, D: Amniotic ectoderm) do not pass through the primitive streak during development. The cytotrophoblast and syncytiotrophoblast are part of the placenta, the yolk sac endoderm is derived from the hypoblast, and the amniotic ectoderm is part of the amnion, which does not form through the primitive streak.

Question 9

A key molecule in the determination of body asymmetry is ________________.&#10;A)Retinoic acid&#10;B)Notch&#10;C)Nodal&#10;D)Bone morphogenetic protein&#10;E)None of the above

Accepted Answer

Nodal is a key molecule in the determination of body asymmetry, specifically left-right asymmetry. It is responsible for initiating a signaling cascade that ultimately determines the left and right sides of the body during embryonic development. Retinoic acid, Notch, and Bone morphogenetic protein are involved in other aspects of development but not specifically in body asymmetry.

Question 10

Neural induction molecules act by blocking the inhibitory action of _________ in the dorsal ectoderm.&#10;A)Bone morphogenetic protein-4&#10;B)Noggin&#10;C)Chordin&#10;D)Fibroblast growth factor&#10;E)Lim-1

Accepted Answer

Neural induction molecules such as Noggin and Chordin act by blocking the inhibitory action of Bone morphogenetic protein-4 (BMP-4) in the dorsal ectoderm, allowing neural tissue to form.

Question 11

The absence of which molecule results in an embryo missing the anterior part of the head?&#10;A)Retinoic acid&#10;B)Lim-1&#10;C)Bone morphogenetic protein-4&#10;D)Chordin&#10;E)None of the above

Accepted Answer

The answer of The absence of which molecule results in...

Question 12

Which of the following tissues arise from cells passing through the primitive streak?&#10;A)Embryonic endoderm&#10;B)Hypoblast&#10;C)Cytotrophoblast&#10;D)Primary yolk sac&#10;E)Amnion

Accepted Answer

The answer of Which of the following tissues arise from...

Question 13

Neural induction occurs through the blocking of what inhibitory molecule?&#10;A)Bone morphogenetic protein-4&#10;B)Activin&#10;C)Sonic hedgehog&#10;D)N-CAM&#10;E)Chordin

Accepted Answer

The answer of Neural induction occurs through the blocking of...

Question 14

As embryonic mesodermal cells pass through the primitive streak,they find themselves in an extracellular environment that is rich in _____________.&#10;A)Histones&#10;B)Hyaluronic acid&#10;C)Protamines&#10;D)All of the above&#10;E)None of the above

Accepted Answer

The answer of As embryonic mesodermal cells pass through the...

Question 15

Which of the structures below will induce a secondary body axis if implanted in a host embryo?&#10;A)Hensen's node&#10;B)Hypoblast&#10;C)Cytotrophoblast&#10;D)Syncytiotrophoblast&#10;E)Amnion

Accepted Answer

The answer of Which of the structures below will induce...

Question 16

The principal inductor in primary neural induction is the _____________.&#10;A)Hypoblast&#10;B)Primitive streak&#10;C)Extraembryonic mesoderm&#10;D)Notochordal process&#10;E)Embryonic ectoderm

Accepted Answer

The answer of The principal inductor in primary neural induction...

Deck 5: Formation of Germ Layers and Early Derivatives