topic 26: embryo I

Question 1

Fertlization

Answer 1

-occurs in ampulla of fallopian tube
-sperm pierces through zona pellucida
-cortical reaction prevents polyspermy
-pronuclei of sperm & egg fuse
-formation of a zygote

Question 2

Implantation

Answer 2

-zona pellucida hatches
- synciotrophoblast invades endometrium & establishes connection with maternal bloo supply
- also releases apoptotic factors that results in death of certain cells lining uterus to create space 4 embryo
- embryo sinks deeper
- endometrium closes up, fully embedding embryo

Question 3

cleavage

Answer 3

-starting point of cleavage is after fertilization
-zygote undergoes series of rapid mitotic divisions and forms cells called blastomeres they are increasing no of cell but not size of embryo
-after numerous division, cells form a solid ball known as morula (16 cell stage )
-blastomeres undergo compaction, and blastocyst is formed
-has 2 main cell population: i.inner cellular mass/embryoblast : will become embryo proper & i.trophoblast : becomes placenta

Question 4

Gastrulation

Answer 4

a blastula, made up of one layer, folds inward and enlarges to create a gastrula
steps:
-primitive streak forms along epiblast
-cell migrate through primitive streak to form mesoderm & endoderm
-remaining epiblast form ectoderm
(notochords forms mesodermal )

Question 5

development of neuroectoderm

Answer 5

-thickened ectoderm forms neural plates
-nerual plates folds to from neural grooves
-neural folds fuse to from neural tube which later on forms central nervous system

Question 6

Differentiation of intraembryonic mesoderm

Answer 6

3 regions:
1.paraxial mesoderm : forms somites to ives rise to verterbrae, ribs & skeletal muscle
2.Intermediate mesoderm : forms urogenital system (kidneys & gonads)
3.Lateral platesmesoderm: splits into somatic & splanchnic layers that will form body wall , circulatory system & visceral organs