|
Home > Preview
The flashcards below were created by user
sabbyfish
on FreezingBlue Flashcards.
-
viviparous
why does this cause problems?
- embryo develops in uterus
- problem because hard to examine embryos in utero
-
Fertilization
- sperm released into female
- capacitation period
- sperm gets to egg and has hyaluronidase that gets them through the cumulus-matrix complex
- ZP3 in zona pellucida recognizes sperm by binding GalT on sperm
- exocytosis of acrosome releases acrosin: a serine-protease that digests a path through zona pellucida so sperm can reach the egg
- sperm reaches the egg
- ADAM proteins on sperm bind to integrins on egg
- the 2 membranes fuse by CD9 on egg and GPI-anchored cell surface proteins
- fusion happens and whole sperm enters egg
-
polyspermy
fertilization by multiple sperm
-
acrosome
- structure at front of sperm cell
- important for fertilization
- filled with serine protease (acrosin) that digests a path through zona pellucida
-
capacitation
- process that makes the sperm competent to fertilize egg
- happens in female reproductive tract
- can be done in vitro with albumin/calcium/bicarbonate solution that activates adenylyl cyclase which increases cAMP and activates protein kinase A = increase in membrane potential, pH, calcium, and motility
-
egg
- oocyte arrested at metaphase II
- surrounded by follicle cells (cumulus cells)
- zona pellucida which is extracellular material
-
zona pellucida
- has special proteins: ZP1, ZP2, ZP3
- ZP3: sperm binds to this, recognizes sperm from same species only
-
egg activation
- after the plasma membranes of the egg and sperm fuse, intracellular calcium concentration increases
- this increase in calcium is a universal response in animals
- calcium transients: calcium concentration fluctuates
- sets in motion many events:
- cortical granules are released and modify zona proteins so they can't bind sperm anymore
- meiotic division completes: 2nd polar body is extruded, sperm nucleus decondenses, pronuclei migrate to each other, DNA replication occurs, chromosomes align for first mitotic division
-
where do centrioles come from?
- in mouse: both come from oocyte
- in most mammals: sperm contributes centriole that becomes microtubule organizing center
-
preimplantation stages
- fertilization in oviduct
- slow cleavage divisions: 12-24 hours per division
- divisions not synchronous
- rotational cleavage
- 8 cell stage: compaction
- 16 cell stage: morula
-
rotational cleavage
- first cleavage meridional
- second cleavage: one cell meridional, one cell equatorial
-
compaction
- at 8 cell stage
- cells express E-cadherin and form tight associations with each other
- these cells are totipotent
-
pluripotent
able to form all the cells of the body but not extraembryonic tissues
-
totipotent
each cell can form an entire embryo including extraembryonic tissues
-
16 cell stage
- morula
- inner cell mass surrounded by trophectoderm
- outer cells pump sodium into morula so water follows = forms blastocoel (cavity)
-
inner cell mass
- will form the embryo
- pluripotent
- express Oct4
- if express Nanog will form epiblast because Nanog suppresses hypoblast fate and promotes epiblast fate
-
trophectoderm
- outer cells surrounding inner cell mass
- will form the trophoblast which will make the chorion
-
Cdx2
- expressed by trophoblast cells
- suppresses the expression of the transcription factors Oct4 and Nanog
-
Nanog
- suppressed hypoblast fate and promotes epiblast fate
- essential for ES cell identity and pluripotency
-
Oct4
- expressed in ICM
- essential for ES cell identity and pluripotency
-
GATA4
- express this if don't express Nanog
- will form hypoblast
-
Early post-implantation
- embryo hatches from zona and implants in uterine wall
- trophoblast proliferates and stimulates proliferation of uterine mucosa (uterine wall) = diciduum formation
- nutrients transported to embryo from mother and growth begins
- egg cylinder stage
- E6.5: primitive streak forms
- E7.5: head process forms anterior to the node
- E8: somites begin to form
- mesoderm and extraembryonic ectoderm grow out to form amnion and chorion
- embryo turning
-
egg cylinder stage
- epiblast forms embryo proper
- hypoblast = primitive endoderm
- visceral endoderm: important extraembryonic tissue
-
E6.5
- Primitive streak: region of convergence and invagination of cells in a gastrulating amniote embryo, marks posterior end. cell movement similar to birds = formation of mesoderm and endoderm
- node forms at anterior end: like fish shield, xenopus dorsal lip, Hensen's node in birds
-
E7.5
head process forms anterior to node: forming notochord, neural plate
-
-
mesoderm and extraembryonic ectoderm grow out to form amnion and chorion
- amnion: extraembryonic tissue that surrounds the embryo
- chorion: extraembryonic tissue that forms the placenta
- allantois: formed by extraembryonic mesoderm, grows and contacts chorion, forms embryonic blood vessels and placenta
- placenta: forms from ectoplacental cone
-
embryo turning
- embryo flips around about its long axis
- this moves the endoderm/mesoderm to facing inside and ectoderm facing the outside
- only happens in rodents
|
|
Get the free mobile app
Take the Quiz
Learn more
Learn more