Lecture 1 Fertilization And Gastrulation Flashcards
Where does fertilization occur?
Distal 1/3 of ampulla
When does cleavage occur
Day 3 (30 hours after fertilization)
When does implantation occur
Day 6
Capacitation
- takes approx 7 hours
- glycoprotein coat and seminal plasma proteins removed from plasma membrane of sperm
Acrosome rxn
Release of enzymes (acrosin) allows passage of sperm through zona pellucida
Hyluronidase
Allows sperm to penetrate corona radiata
Penetration of zona pellucida
Using esterases, acrosin neuraminidase
Zona reaction
- when 1 sperm gets through causes conformational change in zona pellucida meshwork of glycoproteins (becomes rigid)
- release of lysosomal enzymes from cortical granules near oocyte cell membrane
What block polyspermy
Zona reaction
When does morula development occur?
Day 3= 12-32 cells
What days does blastocyst formation occur?
Day 5-7
When does zona pellucida start degenerating and then disappear?
Day 5= begins to degenerate
Day 7= is gone
What does inner cell mass give rise to?
Embryo
What does trophoblast give rise to?
Placenta
What is the final result of week 1?
- 1 layer (embryo)
- inner cell mass
When do assisted reproductive technologies occur?
During week 1
What are some assisted reproductive technologies?
1) in vitro fertilization and embryo transfer
2) cryopreservation of embryos
3) intracytoplasmic sperm injection
what does trophoblast give rise to?
- Cytotrophoblast
- Syncytiotrophoblast
Syncytiotrophoblast
-from trophoblast
-‐ Proteolytic enzymes,
chorionic gonadotropin (hcG)
‐ Responsible for
implantation and initial
signal of pregnancy
Cytotrophoblast
‐ Stem cell layer
‐ Mitotically active
Hydatidiform Mole
– Abnormal trophoblastic proliferation;
-excessive amounts of hCG produced
complete mole results from
• Fertilization of an empty oocyte,
followed by duplication of the sperm
• Or from fertilization of an empty
oocyte by two sperm
Partial mole results from
fertilization of a
normal oocyte by two sperm
clinical features of hydatidiform mole
- Vaginal bleeding
- Pelvic pressure or pain
- Enlarged uterus
- Hyperemesis gravidarum
Choriocarcinomas
Malignant tumor which develops from
hydatidiform mole
what cell layers are present after week 2?
1) – Epiblast • Ectoderm • Amnion • Amniotic cavity 2) hypoblast (only present during wk 2)
hypoblast
– Endoderm
• Prechordal plate
• Primary and secondary yolk sac (umbilical vesicle)
• Extraembryonic mesoderm
prechordal plate
- future site of mouth
- fusion of epiblast and hypoblast
Extraembryonic Coelom:
hollow cavity outside of the
embryo
Extraembryonic Somatic
Mesoderm:
lining the
trophoblast and covering the
amnion
-adjacent to ectoderm
Extraembryonic Splanchnic
Mesoderm:
lining the yolk sac
(umbilical vesicle)
-adjacent to endoderm
Connecting Stalk
• Extraembryonic somatic mesoderm • Forms at embryonic pole • Position changes during development
Primitive Blood
• Extraembryonic
splanchnic mesoderm
• Forms in wall of yolk sac
Chorion
• Extraembryonic somatic
mesoderm
-cytotrophoblast
-syncytiotrophoblast
placenta previa
- placenta implants over internal cervical os
- marginal, total, partial
what happens in week 3?
gastrulation= formation of 3 primary germ layers
Primitive Streak
– Primitive knot (primitive node)
– Primitive groove
– Primitive pit
sacral coccygeal teratomas
- benign abnormal proliferation of cells
- remnant of primitive streak (cells of epiblast)(all 3 germ layers)
notochord
• Midline • Extends from primitive node (knot) anterior to prechordal plate • Template for vertebral column • Induces neural plate
notochordal plate
notochordal process + endoderm
chordomas
– Rare slow growing aggressive neoplasms of bone – Arise from remnants of notochord – Occur in axial skeleton in spheno-occipital region of skull and sacral regions
Allantois
• Endoderm
• Template for umbilical
arteries & vein
• Becomes urachus
paraxial mesoderm
– Somites
• Muscle
• Skeleton (Vertebral)
• Dermis
intermediate mesoderm
– Urogenital
• Kidneys
• Gonads
lateral plate mesoderm
– Connective tissue • Blood • Lymph • Mesenteries • Cardiovascular
