External genitalia develops in the …… of development |
|||||||
a) |
2nd month |
b) |
5th month |
c) |
3rd month |
d) |
1st month |
External genitalia develops in the …… of development |
|||||||
a) |
2nd month |
b) |
5th month |
c) |
3rd month |
d) |
1st month |
(c)
3rd month.
Summary of important development changes in the human embryo
Time from Fertilisation |
Organ Formed |
Week 1 |
Fertilisation cleavage starts about 24 hours after fertilisation cleavage to form a blastocyst 4-5 days after fertilisation. More than 100 cells implantataion 6-9 days after fertilisation |
Week 2 |
The three primary germ layers (ectoderm, endoderm and mesoderm) develop |
Week 3 |
Woman will not have a period. This may be the first sign that she is pregnant. Beginning of the backbone. Neural tube develops, the beginning of the brain and spinal cord (first organs) |
Week 4 |
Heart, blood vessels, blood and gut start forming. Umbilical cord developing |
Week 5 |
Brain developing, ‘Limb buds’, small swelling which are the beginning of the arms and legs. Heart is a large tube and starts to beat, pumping blood. This can be seen an ultrasound scan |
Week 6 |
Eyes and ears start to form |
Week 7 |
All major internal organs developing. Face forming. Eyes have some colour. Mouth and tongue develop. Beginning of hand and feet |
Week 12 |
Foetus fully formed, with all organs, muscles, bones toes and fingers. Sex organs well developed. Foetus is moving |
Week 20 |
Hair beginning to grow including eyebrows and eyelashes. Fingerprints developed. Fingernails and toenails growing. Firm hand grip. Between 16 and 20 weeks baby usually felt moving for first time |
Week 24 |
Eyelids open. Legal limit of abortion in most circumstances |
By Week 26 |
Has a good chance of survival if born prematurely |
By Week 28 |
Baby moving vigorously. Responds to touch and loud noises. Swallowing amniotic fluid and urinating |
By Week 30 |
Usually lying head down ready for birth |
40 Weeks |
Birth |