Question 1

________ Gives rise to the brain and spinal cord
A)Allantois
B)Primitive streak
C)Notochord
D)Blood island
E)Neural plate

Accepted Answer

The neural plate is a thickened area of ectoderm that overlies and extends on each side of the notochord.The neural plate invaginates to form a neural groove.In later development,the neural folds meet dorsally and fuse to form the neural tube.The cranial part of the neural tube develops into the brain,and the longer remaining part forms the spinal cord.The notochord and paraxial mesoderm produce inductive substances that stimulate or induce the overlying ectoderm to thicken and form the neural plate.

Question 2

________ Neural groove
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The neural groove forms as the neural plate invaginates to form a neural fold on each side.The folds later fuse to form the neural tube,the primordium of the central nervous system (brain and spinal cord).The ectoderm lateral to the folds,surface ectoderm,gives rise to the epidermis of the skin.

Question 3

________ Derived from notochordal process
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The notochord arises by transformation of the notochordal process.The notochord is a cellular rod that defines the primordial axis of the embryo.Mesenchymal cells from the somites later surround it and give rise to the mesenchymal bodies of the vertebrae.The notochord within the developing vertebrae later degenerates.

Question 4

________ Embryonic ectoderm
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The embryonic ectoderm in the region indicated forms a neural fold.The neural folds soon fuse,converting the neural plate into the neural tube.

Question 5

________ Gives rise to an adult body cavity
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The intraembryonic coelom in the area indicated becomes part of the peritoneal cavity.The coelom appears here as a space within the lateral mesoderm,splitting it into somatic and splanchnic layers.The transverse section is cut through the caudal region of the lateral extensions of the horseshoe-shaped body cavity or coelom.

Question 6

________ Appears on extraembryonic membranes
A)Allantois
B)Primitive streak
C)Notochord
D)Blood island
E)Neural plate

Accepted Answer

The blood islands first appear on the walls of the umbilical vesicle,allantois,and connecting stalk.These extraembryonic membranes are derived from the zygote,but they are not part of the embryo.Blood islands form in the embryo about 2 days after they appear on the umbilical vesicle.

Question 7

________ Diverticulum of umbilical vesicle (yolk sac)
A)Allantois
B)Primitive streak
C)Notochord
D)Blood island
E)Neural plate

Accepted Answer

The allantois,a diverticulum of the umbilical vesicle,is a vestigial structure that later becomes the urachus (median umbilical ligament in an adult).It serves as a reservoir for excretory products in some species,but it is nonfunctional in human embryos.However,its blood vessels become the umbilical vessels.

Question 8

________ Derived from primitive streak
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The intraembryonic mesoderm is derived from the primitive streak.The primitive streak produces mesoderm rapidly during the third and fourth weeks.

Question 9

________ Derived from paraxial mesoderm
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The somites are paired cubical masses derived by segmentation of the paraxial mesoderm.The first pair of somites is formed a short distance caudal to the tip of the notochord,and successive somites are progressively formed from paraxial mesoderm.Most somites appear between days 20 and 30;they give rise to the axial skeleton and its associated musculature.

Question 10

________ Notochordal process
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The notochordal process is a rod-shaped structure composed of cells derived from the primitive node of the primitive streak.It is the primordium of the notochord,a cellular structure that defines the primordial axis of the embryo.

Question 11

________ Wall of amniotic sac
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The amnion encloses the amniotic cavity,forming an amniotic sac.It contains fluid that bathes the embryonic disc,forming its floor.The wall of this sac consists of an inner epithelial layer of cells covered externally by extraembryonic somatic mesoderm.

Question 12

________ Fusing to form neural tube
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The neural folds are fusing to form the neural tube,the primordium of the brain and spinal cord.These folds form as the neural plate invaginates along its central axis to form a neural groove.

Question 13

________ Source of mesenchyme
A)Allantois
B)Primitive streak
C)Notochord
D)Blood island
E)Neural plate

Accepted Answer

The primitive streak produces mesoderm,which develops into mesenchyme (embryonic connective tissue).Mesenchyme forms a packing tissue around developing organs and develops into connective tissues and muscles.

Question 14

________ Aggregation of angioblasts
A)Allantois
B)Primitive streak
C)Notochord
D)Blood island
E)Neural plate

Accepted Answer

Splanchnic mesenchymal cells known as angioblasts aggregate to form isolated masses called blood islands,which develop into vascular endothelium and primordial blood cells.Blood islands form first on the umbilical vesicle,chorion,allantois,and connecting stalk,but they develop in the embryo about 2 days later.

Question 15

________ Gives rise to most of the embryonic mesoderm
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The primitive streak,a linear band of epiblast,gives rise to mesoderm mainly during the third week.The mesoderm extends laterally and becomes continuous with the extraembryonic mesoderm on the amnion and umbilical vesicle.

Question 16

________ Primitive pit

Accepted Answer

The primitive pit is a depression in the primitive node at the cranial end of the primitive streak.It extends into the notochordal process and forms the notochordal canal.Thus,it is the entrance to the notochordal canal.The pit later forms the opening of the neurenteric canal,which temporarily connects the amniotic cavity with the umbilical vesicle.

Question 17

________ Splanchnopleure
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The splanchnopleure is composed of splanchnic mesoderm and endoderm and represents the future wall of the primordial gut.The endoderm gives rise to the epithelium and glands of the digestive tract,and the mesoderm gives rise to its muscular and fibrous elements.

Question 18

________ Site of the prechordal plate
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The site of the prechordal plate is indicated in the drawing by a dotted oval to indicate that it is not visible from the dorsal surface of the embryonic disc.The prechordal plate is a circular area of thickened embryonic endoderm in the cranial part of the roof of the umbilical vesicle.The prechordal plate,together with the overlying embryonic ectoderm,later constitutes the oropharyngeal membrane.

Question 19

________ Umbilical artery
A)A
B)B
C)C
D)D
E)E

Accepted Answer

The paired umbilical arteries are branches of the dorsal aortae.They transport deoxygenated blood and waste products from the embryo to the chorionic villi of the placenta.

Question 20

________ Forms the basis of the axial skeleton
A)Allantois
B)Primitive streak
C)Notochord
D)Blood island
E)Neural plate

Accepted Answer

The developing notochord and the adjacent paraxial mesoderm are thought to produce inductive substances that stimulate development of the neural plate from the overlying embryonic ectoderm.The notochord forms the basis of the axial skeleton.The vertebrae develop around it,and then it degenerates.In between the vertebrae,the notochord forms the primordium of the nucleus pulposus of the intervertebral disc.

Quiz 3: Formation of Germ Layers and Early Tissue and Organ Differentiation

________ Gives rise to the brain and spinal cord

________ Neural groove

________ Derived from notochordal process

________ Embryonic ectoderm

________ Gives rise to an adult body cavity

________ Appears on extraembryonic membranes

________ Diverticulum of umbilical vesicle (yolk sac)

________ Derived from primitive streak

________ Derived from paraxial mesoderm

________ Notochordal process

________ Wall of amniotic sac

________ Fusing to form neural tube

________ Source of mesenchyme

________ Aggregation of angioblasts

________ Gives rise to most of the embryonic mesoderm

________ Primitive pit

________ Splanchnopleure

________ Site of the prechordal plate

________ Umbilical artery

________ Forms the basis of the axial skeleton