Fertilization And Implantation Flashcards
When does fertilization occur?
What does this allow for?
Day 15-16 of menstrual cycle
Recombination of genetic material and initiation of events that begin embryonic development
Where are do the sperm and the oocyte have to go to be fertilized?
What leads to follicular rupture?
What is ejected into the peritoneum?
What sweeps the oocyte into the oviduct?
Ampulla of oviduct
LH surge
Ovum and surrounding corona radiata
Fimbriae
The sperm enter the ____ near the uterus; 200 million reach the ____ of the oviduct.
What are the barriers the sperm face?
Cervical mucus and myometrium contractions are a result of increased ____ near ovulation period. This allows ____ to form to allow motile sperm to pass through; ____ help move sperm through the cervix/uterus.
Vagina; ampulla
Distance, immune, secretory, timing
Estrogen; channels; contractions
Sperm undergo ____ in order to fertilize the oocyte.
Where?
What are the modifications of spermatozoan caused by capacitation?
Capacitation
Female oviduct
Altered membrane fluidity due to removal of cholesterol
Removal of various proteins, carbs, and glycoproteins from the membrane that may block binding sites
Change in membrane potential that may permit Ca influx and the acrosome reaction
Phosphorylation of various proteins
Incapacitated sperm bind actively to epithelial cells of the ____. They become unbound when they are _____.
Binding slows the capacitation process, extends ___ lifespan, prevents too many sperm from reaching the ____, increased the probability the sperm will be in the ____ when the egg is ovulated; also called sperm ____.
Oviductal isthmus; capacitated
Sperm; egg; oviduct; reservoir
Hyperactivation of sperm is caused by what?
Involves a change in _____ motion from wavelike to ____. It is necessary for sperm to detach from the _____ epithelium. It increased the ____ in thick oviductal fluid and helps propel sperm through outer layers of the _____ and _____ of the egg.
Sperm capacitation and chemical signals from oocyte
Flagellar; whiplike; oviductal; mobility; cumulus and zona pellucida
Fertilization is a process by which multiple sperm bind to the ____ but only one fertilizes the ____.
What three barriers of the egg must be breached by the sperm?
Corona radiate; egg
Expanded cumulus (corona radiata)
Zona pellucida
Plasma membrane of the egg (oolemma)
The cumulus cell matrix is covered with ____; the sperm digest this with membrane bound _____.
Hyaluronic acid; hyaluronidase
What glycoproteins comprise the zona pellucida?
The sperm contain ____ receptors.
Binding of ZP3 receptor to ZP3 triggers ______. This causes the inner sperm membrane to fuse with the outer acrosomal membrane to release the contents of ____. The ____ receptors are lost and become ZP2
The enzymes in the acrosomal vesicle digest the _____ and sperm enter.
ZP1, ZP2, ZP3, ZP4
ZP3
Acrosome reaction
Acrosomal vesicle
ZP3
Zona pellucida
When the sperm reach the plasma membrane, they are involved with ___ proteins that bind to a sperm protein called ____. The entire ____ enters the edge during fusion, sperm DNA instantly _____.
What forms around the DNA and what is its fx?
Tetraspanin; Izumo
Sperm; decondenses
Membrane called pronucleus (stimulates the oocyte to begin its meiosis II process)
What are assisted reproductive techniques?
Ovulation induction
Artificial insemination (AI)
Gamete transfer
In-vitro fertilization (IVF)
Intracytoplasmic sperm injection (ICSI)
What triggers the cortical reaction?
What is released during this reaction?
What does this prevent?
What forms the physical barrier?
Fusion of sperm and egg
Release Ca, alteration of ZP2 -> ZPf, hyaluronic acid, proteoglycans, and proteinases
Blocks binding of additional sperm, preventing polyspermy
Zona pellucida
___ release stimulates the oocyte’s completion of meiosis II. This breakdowns ___ proteins and _____ is released.
When the egg is activated, ____ condenses. ____ forms around female chromosomes. Male and female chromosomes replicate as _____ move together. Fusion of pronuclei initiates ______.
MAPK; 2nd polar body
DNA; pronucleus; pronuclei; first embryonic cleavage (first embryonic development)
Describe the timing of pregnancy:
Day 0? 0-3 weeks? 3-8 weeks? 8 weeks-term? Total gestation time?
Moment of fertilization
Early development
Embryonic period (organogenesis)
Fetal period
38 weeks
What happens during week one of embryonic development?
What happens on day 3?
Day 4?
Days 6-8?
Cleavage (cell division without growth)
Embryo reaches 16 cell stage (morula)
Early blastocyst
Implantation
During embryonic cleavage, individual cells become ____.
Mitotic divisions maintain ____ complement.
Blastomeres are ____.
Embryo reaches the 16 cell morula by day ____.
Blastomeres
2N (diploid)
Totipotent
3
The outer cells of the morula increase cell to cell adhesion via ____ and ____.
They form ____ and increases Na and osmosis to form a _____.
Inner cells become inner cell mass and will form the ____ which is considered ____.
Desmosomes; tight junctions
Trophoectoderm; blastocele
Embryo proper; pluripotent
What is a dizygotic twin?
What is monozygotic twinning and when do the cells usually divide?
What is caused during an early division of totipotent cells?
What is caused when there is a division of the inner cell mass?
What is caused when there is a incomplete division of the inner cell mass?
Female ovulates two oocytes and they are both fertilized
From one zygote; type of twinning depends on when there is a division in the cells, usually in the cleavage/blastocyst stage
Early division when the cells are totipotent = two individual embryos, same genetic material, each with own placenta
Division of the inner cell mass within blastocoele = share chorion, individual amniotic sacs or share sacs
Incomplete division of the inner cell mass = conjoint twins
Embryo hatches from the _____ prior to implantation. ____ secrete proteases that digest the zona pellucida.
Inability to hatch results in _____. Premature hatching resulted in ____.
Zona pellucida; trophoblasts
Infertility; abnormal implantation
What does the blastocyst synthesize and secrete?
Examples?
Molecules that promote the maintenance of pregnancy, promote implantation and placental development
Secretion of immunosuppressive and immunoregulatory factors, hCG
What secretes human chorionic gonadotropin (hCG)?
When is this measured?
What is its fx?
Trophoblasts and syncytiotrophoblasts
8 days post ovulation
Prevents involution of the corpus luteum therefore preventing menstruation and allowing the corpus luteum to secrete progesterone and estrogen
Autocrine growth factor: stimulates trophoblast growth and development, stimulates placental growth
Pre-implantation the blastocyst is bathed in ____. This draws O2 and necessary metabolic substances for ____ and ____. Exchange is via ____.
The blastocyst eventually needs a more intimate association with the uterus therefore develops the ____.
Uterine secretions; growth and survival; diffusion (O2/CO2)
Placenta
Typical implantation occurs in the posterior wall of the ____.
This is an invasive, interstitial implantation with adhesion-supported invasion and migration of ____ cells. ____ enzymes break down the extracellular matrix.
The attachment of the blastocyst initiates differentiation of the _____. There are rapidly proliferating _____ that initially provide a feeder layer of continuously dividing cells.
Uterine fundus
Trophoblastic; hydrolytic
Trophoblast; cytotrophoblasts
What are the fx of syncytiotrophoblasts?
They express ____ proteins that initially bind uterine and surface epithelia, then as the embryo implants, they bind to components of the ______.
They breakdown ____ through secretions of _____ and other hydrolytic enzymes.
They secrete ____, which maintains the viability of the corpus luteum for ___ secretion.
They are highly steroidogenic at ___ weeks and make enough ____ to maintain a pregnancy independent of corpus luteum.
As implantation and placentation progress, syncytiotrophoblasts fx in ____ and _____ of gases, nutrients, and wastes.
Adhesive (cadherins and intergrins); uterine extracellular matrix
Extracellular matrix; matrix metalloproteases
hCH; progesterone
10; progesterone
Phagocytosis; bidirectional placental transfer
