EMB: Fertilization & Gastrulation Flashcards
When it’s said the embryo is 6 weeks along clinically, what is the actual age of the embryo?
4 weeks
When does the obstetrical/gestational/menstrual calendar begin?
How far ahead is the Fertilization calendar?
1st day of the females last menstrual cycle
2 weeks after
Embryology focuses on what trimester?
first trimester
NOTE: fetal development is second and third trimester
Which layer of the human ovum is an amorphus, acellular, proteoglycan meshwork?
A. Corona Radiata
B. Zona Pellucida
C. Nucleus
D. Perivitelline space
E. Plasma Membrane
Zona Pellucida
What is found in the head of the sperm?
Acrosome surrounding the Nucleus (23 X or 23Y)
What portion of the human sperm posses mitochondria?
A. End tail piece
B. Principal piece of tail
C. Middle Tail Piece
D. Neck
Middle Tail Piece
Cleavage, Formation of the blastocyst, inner cell mass, and implantation starts at what day and goes until when?
Day 0 to Day 7
(ovulation + fertilization)
What is capacitation?
How long does it take?
Removal of glycoprotein coat from acrosome as the sperm moves through
7 hours
Capacitation = lid removal
The passage of sperm through the ovum’s corona radiata must occur in order for the sperm to get to the Zona pellucida. Getting through the corona radiata is a group effort by sperm that requires what enzyme?
Hyaluronidase
Once sperm pass through the corona radiata, the sperm attempt to penetrate the Zona Pellucida. What enzymes are released by sperm to erode the ZP?
What is the principal enzyme?
Esterases
Acrosin
Neuraminidase
Remeber: EAN
Once sperm reach the zona pellucida the zona reaction occurs.
What is the goal of the zona reaction?
How does it occur?
Blocks polyspermy
Changes conformation that only allows one sperm in, and traps the other sperm in the ZP
What portion of the sperm enters the oocyte cytoplasm after fusion of plasma membranes?
Head and Tail
About how long does fertilization take?
24 hours
What are results of fertilziation? (5)
Completion of 2nd meiotic division
diploid # of chormosomes
sex determination
metabloically active oocyte
initiation of cleavage
Cleavage increases cell number while decreasing cell size. At what point does cleavage produce the morula (past 8 cell stage)?
After the morula is formed we go on to form the blastocyst. When does this enter the uterus?
Day 3
Day 4
Fertilization = day 0
What day does the blastocyst no longer have a zona pellucida around it? This is also known as “hatching”
Day 7
NOTE: at Day 5 it’s still present, Day 6 it degrades, Day 7 its gone
What is another name for inner cell mass?
What is the stem cell layer for the placenta?
Embryoblast
Trophoblast
At week one we have the late blastocyst which is comprised of what 3 main things?
Inner cell mass
Blastocyst cavity
Trophoblast layer
In In-vitro fertilization, mature oocytes are collected during a laparoscopy, and placed in a petri dish with capacitated sperm. Cleavage is allowed to occur in the medium, and cells are collected and embryos are transferred into the uterus. What cell stage are the embryos?
4-8 cell stage
Embryonic stem cells are collected from what portion of the blastocyst?
Inner cell mass
What structure releases early pregnancy factor?
What is the result of releasing early pregnancy factor?
Trophoblast
Immunosuppressive so the body doesn’t reject the embryo as foreign
Gives rise to cytotrophoblast and synctiotrophoblast