Embryonic development

Question 1

define fertilisation

Answer 1

Is the fusion of the sperm and ova

Question 2

define implantation

Answer 2

The process whereby an embryo (blastocyst) sinks into the endometrium

Question 3

where does fertilisation occur

Answer 3

The fallopian tubes

Question 4

where does implantation occur

Answer 4

Occurs at the endometrium

Question 5

define zygote

Answer 5

The fertilised ovum from which a new individual develops

Question 6

define embryo

Answer 6

An embryo is the early stage of development of an organism in a human, from fertilisation to the end of the 8th week

Question 7

Relate a zygote to the stages of embryonic development

Answer 7

A zygote goes through many divisions after fertilisation during the cleavage stage. 2 cells - 4 cells - 8 cells - 16 cells. A solid ball of cells will form called a morula. The morula moves down the fallopian tubes and changes to a blastocyst. The blastocyst will embed itself into the endometrium through implantation.

Question 8

describe the embryonic cycle

Answer 8

After the cleavage stage, the blastocyst will embed itself into the endometrium. The embryonic knot will transform into the primary germ cells. The germ layer can now grow and differentiate by absorbing nutrients. The amniotic membrane and yolk sac will form. The germ layer will bend to form a cylinder shape, which causes the amniotic membrane to increase in size and the yolk sac to decrease in size. A body stalk forms which attaches to the germ layer.

Question 9

Discuss how the roles of the placenta establish viable pregnancy during the embryonic cycle

Answer 9

The placenta is an organ that supplies nutrients and removes wastes from the foetus. Chorionic villi develop from the chorion membrane and contain blood vessels. As the baby’s chorionic villi penetrate the endometrium, it becomes surrounded by the mother’s blood. The placenta is attached to the foetus via the umbilical cord, which consists of umbilical veins and arteries. The arteries release wastes and CO2 and absorb nutrients and O2 through the veins, all by diffusion and active transport.

Question 10

how long is the embryonic period

Answer 10

8 weeks

Question 11

what is the function of the amniotic fluid

Answer 11

This fluid serves to protect the embryo against physical injury by acting as a shock absorber

Question 12

what does the ectoderm form

Answer 12

• skin
• hair
• entire nervous system

Question 13

what does the mesoderm form

Answer 13

• bones
• blood
• muscles

Question 14

what does the endoderm form

Answer 14

• alimentary canal
• the lining of the lungs
• epithelium of gall bladder

Question 15

structural changes during the embryonic cycle

Answer 15

week 4 -

• development of muscle segments
• brain begins to form
• heart and liver begin to form

week 5 -
- arm and legs begin to form

week 6 -

• all organs are present (not all functional)
• eyes appear like slits

Question 16

how long does the process of fertilisation to implantation take

Answer 16

6-12 days

Question 17

how long after fertilisation do we refer to a developing baby as a zygote

Answer 17

3-5 days

Question 18

distinguish between embryo and foetus

Answer 18

An embryo is the early stage of development of an organism in a human, from fertilisation to the end of the 8th week. A foetus is a developing individual after the second month of pregnancy.