embryonic development

Question 1

fertilisation zygote

Answer 1

• the sperm and egg join to form a zygote; the cell of a new individual
• fertilization occurs in the fallopian tubes
• the zygote begins rapid mitotic cell division
• beginning of human development

Question 2

clevage

Answer 2

• these mitotic divisions in the early embryo are known as clevage

Question 3

embryo

Answer 3

• the zygote undergoes rapid mitotic development
• the first mitotic division from 1 cell (zygote) to 2 cells marks the start of the embryonic stage
• the embryo starts to move along the fallopian tube, dividing into 4 cells, 8 cells, 16 cells in a solid mass.

Question 4

Blastocyst

Answer 4

• 5 days after fertilisation the embryo is now known as the blastocyst
• a fluid-filled structure with an inner mass (tissue of embryo) of cells surrounding by an outer layer of cells (placenta)
• the blastocyst has reached the uterus where it attaches to the urerine wall.

Question 5

Implantation

Answer 5

• the attachment of the embryo to the uterine wall is known as implantation
• the process of implantation is complete by about day 9 after fertilisation

Question 6

gastrulation

Answer 6

gastrulation is the movement of cells from the inner cell mass to form a 3-layered structure - primary germ layers
* each layer is made of stem cells that differentiate into all the different types of body cells

Question 7

what are the 3-layered structures of gastrulation

Answer 7

• ectoderm
• mesoderm
• endoderm

Question 8

ectoderm

Answer 8

ectoderm; forms the outer layer. these cells go on to form skin, brain and nervous system, pituitary gland, sense organs (such as eyes, ears and etc)

Question 9

mesoderm

Answer 9

mesoderm; form the middle layer. these cells go on to form heart and blood vessels, reproductive and excretory systems, muscle, cartilidge, bone, bone marrow, blood cells.

Question 10

endoderm

Answer 10

endoderm; forms the inner layer. these cells go on to form gastrointential tract, respiratory tract. Respiratory systems, livers, pancreas, gall bladder, and endocrine gland such as thymus.

Question 11

the stages from egg to implantation

Answer 11

1. follicle (ovary)
2. ovulated egg
3. ferlization(day 0)
4. zygote (day 0)
5. 2 cells (day 2)
6. 4 cells (day 3)
7. morula (day 4)
8. inner cell mass of blastocyst (blastocyst)
9. blastocyst implanting (day 7)