Fertilization and early development Flashcards
Capacitation-
involves change in the sperm plasma membrane (glycoprotein and lipid content changes) resulting in increased fertilizability
involves change in the sperm plasma membrane (glycoprotein and lipid content changes) resulting in increased fertilizability
Capacitation
Zona pellucida-
Surrounds oocyte; composed of sulfated glycoproteins ZP-1,2, and 3. ZP-2 and ZP-3 form long extracellular filaments that are cross linked by ZP-1.
surrounds oocyte; composed of sulfated glycoproteins ZP-1,2, and 3. ZP-2 and ZP-3 form long extracellular filaments that are cross linked by ZP-1.
Zona pellucida
ZP-3-
sulfated glycoprotein of the zona pellucida that acts a sperm binding receptor. Binding activated sperm plasma membrane H+ and Na+ transporters as well as Ca2+ transporter increasing sperm cytosolic pH and causing influx of Ca++ which triggers exocytosis of the acrosome
sulfated glycoprotein of the zona pellucida that acts a sperm binding receptor. Binding activated sperm plasma membrane H+ and Na+ transporters as well as Ca2+ transporter increasing sperm cytosolic pH and causing influx of Ca++ which triggers exocytosis of the acrosome
ZP-3
Acrosomal reaction-
sperm binds to ZP-3 sulfated glycoprotein of the zona pellucida, H+, Na+, and Ca++ transporters are activated causing exocytosis of the acrosome releasing it’s contents into the oocyte.
sperm binds to ZP-3 sulfated glycoprotein of the zona pellucida, H+, Na+, and Ca++ transporters are activated causing exocytosis of the acrosome releasing it’s contents into the oocyte.
Acrosomal reaction
Izumo-
sperm protein associated with sperm egg plasma membrane fusion
sperm protein associated with sperm egg plasma membrane fusion
Izumo
CD-9-
egg protein associated with sperm/egg plasma membrane fusion
egg protein associated with sperm/egg plasma membrane fusion
CD-9
Zona reaction-
Cortical granule exocytosis- Ca++ released from egg ER by IP3 from sperm/egg plasma membrane fusion causes release of granule contents to extracellular space which inhibits the ability of ZP-3 to bind with sperm and “hardens” the zona preventing polyspermy
Cortical granule exocytosis- Ca++ released from egg ER by IP3 from sperm/egg plasma membrane fusion causes release of granule contents to extracellular space which inhibits the ability of ZP-3 to bind with sperm and “hardens” the zona preventing polyspermy
Zona reaction
Aside from preventing polyspermy, what is another important result of Ca++ increase after fusion-
the egg chromosomes which have been arrested in metaphase 2, continue dividing with the destruction of CSF and activation of APCs. This creates the pro-nucleus of the egg (other half of DNA is exocytosed). Pro-nucleus of sperm is also created and both pro-nuclei enter S phase in preparation for first cleavage division. The pro-nuclei are pushed together by microfilaments and microtubules to for metaphase plate and new unique individual is formed. This is the culmination of fertilization.
oligospermia:
reduced numbers of sperm
asthenospermia:
reduced motility of sperm
teratozoospermia:
altered sperm morphology
Cleavage-
a series of mitotic cell divisions that occur as the embryo moves down the oviduct toward the uterus. (week one)
Blastomeres-
~16 sphereical cells comprising the embryo around day four or five which terms the embryo a morula
~16 sphereical cells comprising the embryo around day four or five which terms the embryo a morula
Blastomeres
Morula-
stage of embryo when it is comprised of ~16 spherical cells
stage of embryo when it is comprised of ~16 spherical cells
Morula
Compaction-
a change in the way blastomeres of the morula interact with eachother. Tight and gap junctions form and cells flatten together to form a ball. Cadherins play an important role here. Also embryo becomes more polarized to for distinct apical and basal surfaces and blastocoel forms. Embyo is now called a blastocyst
a change in the way blastomeres of the morula interact with eachother. Tight and gap junctions form and cells flatten together to form a ball. Cadherins play an important role here. Also embryo becomes more polarized to for distinct apical and basal surfaces and blastocoel forms. Embyo is now called a blastocyst
Compaction
Blastocyst-
the embyo after blastocoel has formed during compaction.
the embyo after blastocoel has formed during compaction.
Blastocyst
Hatching-
at the 6-7 day mark, the blastocoel reaches the uterus and get ready to implant by shedding the zona pellucida by realizing hydrolytic enzymes.
at the 6-7 day mark, the blastocoel reaches the uterus and get ready to implant by shedding the zona pellucida by realizing hydrolytic enzymes.
Hatching
Trophoblast-
the outer cells of the embryo that go on to form the placenta
the outer cells of the embryo that go on to form the placenta
Trophoblast
Syncytiotrophoblast-
formed by the fusion of a portion of the embryonic trophoblast with the epithelial cells of the uterine endometrium. Invades the uterine stroma and contacts maternal circulatory system which begins to nourish the embryo
formed by the fusion of a portion of the embryonic trophoblast with the epithelial cells of the uterine endometrium. Invades the uterine stroma and contacts maternal circulatory system which begins to nourish the embryo
Syncytiotrophoblast
Cytotrophoblasts-
trophoblast cells that do not fuse with the endometrium and divide via mitosis to add cells to the rapidly proliferating syncytiotrophoblast
trophoblast cells that do not fuse with the endometrium and divide via mitosis to add cells to the rapidly proliferating syncytiotrophoblast
cytotrophoblast
Ectopic implantation-
abnormal site of implantation
Human chorionic gonadotropin-
(HCG) secreted by the syncytiotrophoblast to maternal blood stream causing maternal release of estrogen and progesterone to prevent the sloughing of the endometrium and allow maintenance of the pregnancy
(HCG) secreted by the syncytiotrophoblast to maternal blood stream causing maternal release of estrogen and progesterone to prevent the sloughing of the endometrium and allow maintenance of the pregnancy
Human chorinic gonadotropin
Decidual reaction-
trigger by the invasion of the syncytiotrophoblast into the endometrium. Endometrial cells surrounding the embryo begin to accumulate glycogen and lipids.
trigger by the invasion of the syncytiotrophoblast into the endometrium. Endometrial cells surrounding the embryo begin to accumulate glycogen and lipids.
Decidual reaction
Decidual cells-
created from endometrial cells that stock up on lipid and glycogen after invasion of syncytiotrophoblasts. They surround the embryo to form the decidua.
created from endometrial cells that stock up on lipid and glycogen after invasion of syncytiotrophoblasts. They surround the embryo to form the decidua.
Decidual cells
Decidua-
decidual cells surrounding the embryo. One function may be to protect the embryo from the maternal immune system.
Bilaminar disc-
flattening of the inner cell mass to form two layers, the epiblast and the hypoblast. The hypoblast is away from the site of fusion and cells are cuboidal, epiblast is adjacent to the site of fusion and newly forming amniotic sac and cells are columnar
flattening of the inner cell mass to form two layers, the epiblast and the hypoblast. The hypoblast is away from the site of fusion and cells are cuboidal, epiblast is adjacent to the site of fusion and newly forming amniotic sac and cells are columnar
Bilaminar disc
Animal pole-
the inner cell mass, as opposed to the trophoblast
Amniotic cavity-
fluid space between the inner cell mass and adjacent trophectoderm
fluid space between the inner cell mass and adjacent trophectoderm
amniotic cavity
Epiblast-
layer of bilaminar disc adjacent to the amniotic cavity; will eventually give rise to the embryo as well as extraembryonic structures. Identifies the dorsal section of the embryo
layer of bilaminar disc adjacent to the amniotic cavity; will eventually give rise to the embryo as well as extraembryonic structures. Identifies the dorsal section of the embryo.
Epiblast
Hypoblast-
layer of the bilaminar disc that is not adjacent to the amniotic cavity and will only give rise to extraembryonic structures; ie. Yolk sac. Identifies the ventral aspect of the embryo.
Extraembryonic mesoderm-
cells that break free of the primary yolk sac (around day 9) and fill the space between the embryo and the trophoblast. A dense cluster of these cells will give rise to the umbilical chord.
cells that break free of the primary yolk sac (around day 9) and fill the space between the embryo and the trophoblast. A dense cluster of these cells will give rise to the umbilical chord.
Extraembryonic mesoderm
layer of the bilaminar disc that is not adjacent to the amniotic cavity and will only give rise to extraembryonic structures; ie. Yolk sac. Identifies the ventral aspect of the embryo.
Hypoderm
Gastrulation-
mass migration of cells to form three germ layers; ectoderm, endoderm, mesoderm. All are derived from the epiblast.
mass migration of cells to form three germ layers; ectoderm, endoderm, mesoderm. All are derived from the epiblast.
Gastrulation
Primitive streak-
thickening of epiblastic cells to demarcate the left/right and anterio/posterior axis of the embryo
thickening of epiblastic cells to demarcate the left/right and anterio/posterior axis of the embryo
Primitive streak