First 3 weeks of development

Question 1

What are the 5 stages of development in the first 72hrs?

Answer 1

• Zygote
• 2 cell (30hr)
• 4 cell (40hr)
• 8 cell
• Morula (72hr)

Question 2

What surrounds the morula?

Answer 2

zona pellucida

Question 3

Where does the morula travel to and implant?

Answer 3

travels down the fallopian tubes and implants in the endometrium (fundus or posterior wall of the uterine wall)

Question 4

What happens to the morula at the time of implantation?

Answer 4

fluid begins to accumulate in the intracellular spaces and merge to form a single cavity

Question 5

What does the inner cell mass form?

Answer 5

differentiate to form primary germ layers;

• ectoderm
• endoderm

Question 6

What is the process of differentiation of the inner cell mass referred to as?

Answer 6

gastrulation

Question 7

What occurs at day 8?

Answer 7

embryoblast differntiates into epiblast and hypoblast to form a bilaminiar disc

Question 8

What is the small cavity that appears within the epiblast called?

Answer 8

amniotic cavity

Question 9

What is the primitive streak?

Answer 9

shallow groove on the dorsal side of the bilaminar disc; caudal region = inferior end

Question 10

At what day does a trilaminar disc form?

Answer 10

17

Question 11

What occurs on day 17?

Answer 11

Epiblast cells migreate through the primitive streak and create a 3rd layer between the epiblast and hypoblast

Question 12

Epiblast

Answer 12

Ectoderm

Question 13

Hypoblast

Answer 13

Endoderm

Question 14

Middle layer =

Answer 14

mesoderm

Question 15

What happens to form the notochord

Answer 15

Prenotochordal cells migrate through the primitive streak to form the notochordal plate within the endoderm. It then detaches to form the notochord which activates the signalling pathway involbed in tissue differentiation and development

Question 16

Paraxial

Answer 16

Somites

Question 17

Intermediate

Answer 17

Urinary and genital

Question 18

Lateral

Answer 18

body walls and cavities