Third Week of Development

Question 1

Gastrulation

Answer 1

process of establishing 3 germ layers and begins with the formation of the primitive streak

Question 2

Cells of the epiblast migrate towards to the primitive streak, detach, and slip underneath the epiblast in a process called what?

Answer 2

invagination

Question 3

Mesenchymal cells migrate cranially from the primitive node and pit forming a median celluar cord called what?

Answer 3

the notochordal process, this process aquires a lumen known as the notochordal canal

Question 4

The prechordal plate will be important in the develpment of the _____ while the notochord will be the basis for the formation of the parts of the ____________________.

Answer 4

forebrain, axial skeleton and spinal cord

Question 5

What does the cloacal membrane form?

Answer 5

the anus

Question 6

When are body axes formed?

Answer 6

before and during the time of gastrulation

Question 7

When does the primitive streak regress?

Answer 7

the end of the fourth week

Question 8

The beginning of the 3rd week of development (gastrulation) is a highly sensitive period for what?

Answer 8

teratogenesis and malformations

Question 9

Holoprosencephaly

Answer 9

high doses of alcohol at the gastrulation stage kills cells in the anterior midline of the germ disc producing a deficiency of the midline in craniofacial structures, fore brain is small

Question 10

Sirenomelia

Answer 10

insufficient mesoderm formed in the caudal most region of the embryo , abnormalities in the lower half of body, absent of fused lower limbs (sometimes associated with maternal diabetes)

Question 11

Situs inversus

Answer 11

left and right organ positions are reversed

Question 12

Sacrococcygeal teratoma TEST QUESTION

Answer 12

proliferation of remnants of the primitive streak, forms tumors in all 3 germ layers, most common tumor in newborns