Development II- Lecture 9/21/21 Flashcards
Corpus luteum secretion
Secretes progesterone until 20 weeks of gestation
hGH
Human chorionic gonadotropin, secreted from the implanted blastocyst, tells corpus luteum to keep secreting progesterone
Sperm transport
Swim faster in alkaline environments, varying with pH, moves along by uterine contractions stimulated by PGE2 in semen
Minimum sperm level for fertility
About 10 million/mL
Normal sperm concentration
100 million/mL of ejaculate, usually about 2-6 mL
Sperm capacitation
Takes 6-8 hrs, glycoproteins coat removed from acrosome surface and can swim and fertilize
Acrosome rxn
Initiated when bing to ZP3, causes membrane to perforate, releasing enzymes that can break down the matrix
The eureka moment (fusion)
Plasma membranes of the oocyte and sperm fuse, official start of fertilization (takes 24 hours), egg completes meiosis II
Cortical reaction
Blocks polyspermy, membrane fusion triggers rapid and massive exocytosis of the cortical granule contents, destroys ZP3 and cross links matrix proteins
ZP3
Zona pellucida protein 3, protein recognized by sperm, species specific
Cortical granule
Contains enzymes for cross linkages, rests just below plasma membrane, derived from the lysosome
Calcium wave
happens when oocyte is penetrated, stimulates meiosis II
Nucleus fusion
Oocyte chromosomes decondense and form a pro nucleus, new sperm nucleus forms pro nucleus, nuclei fuse and all chromosomes replicate, end of fertilization
Results of fertilization (3)
- Stimulates the secondary oocyte to complete meiosis II
- Restores diploid number
- Determines the sex
Polyspermy
Can cause a trip load zygote, account for 20% of spontaneous abortion, only a few survive to birth, only last a couple days
Blastomeres
Early cells after replication, all identical and all replicate together, no bigger because of zona pellucida
Trophoblast
Cells that will go on to form the placenta (about day 3-4)
Inner cell mass
Embryonic stem cells that will form the fetus
Hatching
The shedding of the zona pellucida at day 4-5 which permits the embryo to implant
Gastrualtion
The three germ layers form
Late blastocyst
Forms at day 12-14, about a week after beginning implantation
Implantation completion
At about the end of 2 weeks after fertilization, bilaminar embryonic disc forms
Pre-implantation genetic diagnosis
Blastomeres can be removed for PGD, not, take some of the trophoblasts from blastocysts
Timing of formation of blastocyst
4-5 days post fertilization
Blastocoel cavity
Where the cells of the blastocyst secrete their fluid to facilitate hatching