Embryologt Flashcards
Steps of fertilization (3)
- Capacitation
- Acrosome reaction
- Fusion of the plasma membrane of sperm and oocyte
Describe step 1 of fertilization
- Capacitation
Removal of seminal proteins from the surface
Penetration through corona radiata
Describe step 2 of fertilization
- Acrosome reaction
release of acrosomal enzyme
penetration through zona pellucida
Describe step 3 of fertilization
- Fusion of membrane of sperm and oocyte
Changes in zona pellucida inactivates sperm receptors and prevents polyspermy
Where does fertilization occur?
Ampulla of fallopian tube
Describe fusion of sperm and oocyte
sperm and oocyte forms pronucleus of each, Then pronuclei fuses, restoring the normal diploid number. Then, mitotic division and cleavage begins
What is blastomere?
identical daughter cells of zygote with same sizes
Name for 16-32 blastomere
Morula (day3)
What is blastocyst?
day 4-6 where fluid from uterine cavity fills the blastocystic cavity and inner cell mass/embryoblast is formed.
what does inner cell mass develop into
inner cell mass > embryoblast > embryo
What does peripheral cell develop into?
peripheral cell> trophoblast > fetal component of the placenta
Where does implantation occur?
posterior wall of body of uterus close to the fundus
After blastocyst implant on endometrium, trophoblasts differentiates into two layers. What are those?
inner layer of cytotrophoblast
outer layer of syncytiotrophoblast
Role of cytotrophoblast
mitotically active, MAKE cells and contributes cells to the syncytiotrophoblast
Role of syncytiotrophoblast
erode endometrial connective tissue enabling the blastocyst to “burrow” into endometrium for implantation.
Relationship between syncytiotrophoblast with early pregnancy test
Syncytiotrophoblast secrete HCG human chorionic gonadotrophin which is detected at early pregnancy test.
After implantation, embryoblast changed into embryonic disc which is made up of two layers. What are those?
- Epiblast
2. Hypoblast
Role of epiblast
thicker layer, consisting of columnar cells, forming 3 germ layers
Role of hypoblast
small cuboidal cells, that become yolk sac
What is gastrulation?
formation of three germ layers
What happens to epiblast during gastrulation?
develop into trilaminar disc with three layers, endoderm mesoderm and ectoderm
3 Groups of mesoderm
lateral, intermediate paraxial
Intermediate mesoderm
urogenital organs and ducts
Paraxial mesoderm
one, muscle, skin
lateral mesoderm
heart, spleen, adrenals,
