Class 9: Fertilization Flashcards Preview

Reproductive Biology > Class 9: Fertilization > Flashcards

Flashcards in Class 9: Fertilization Deck (28):

Ampulla of the oviduct:

Top region of the oviduct where egg travels from ovary after ovulation (release from ovarian follicle)


Prophase I arrest

Oocytes are arrested at prophase I until puberty when luteinizing hormone (LH) induces resumption of meiosis of follicle-enclosed oocytes. 2N 4C


Metaphase II arrest:

oocyte (meiotic) maturation to Metaphase II arrest (progress through meiosis I into meiosis II.) The egg will remain in this arrest as 1N 2C, essentially frozen until fertilization occurs. The egg is poised here, waiting for hormones to kick off, and will not complete meiosis unless fertilized. NOTE: egg is never really 1N 1C because final metaphase doesn’t happen until sperm enters.


Cumulus layer, cumulus cell (formerly granulosa cell)

cumulus cells are the granulosa cells from the follicle that are associated with and surround the egg


Zona pellucida

the egg coat, synthesized and secreted by the oocyte during oogenesis. Composed of glycoproteins. Functions include: supports sperm interaction (the sperm can interact with the ZP glycoproteins), can help induce the sperm to undergo acrosome exocytosis, and later encases and protects the embryo during preimplantation development.


Epididymal maturation

sperm in the testis are essentially “useless” they cannot swim yet or fertilize eggs. When sperm pass through the epididymis they mature and acquire motility and the ability to undergo capacitation.


Seminal vesicle, prostate, bulbourethral gland

provide key components of semen which are mixed with the seminal fluids - nutrients, mucus and buffering components.



composed of sperm, nutrients, mucus and buffering components.



physiological changes in sperm that confer the ability/capacity to fertilize an egg, activated through second messenger cAMP and signal transduction cascade. Notable changes: loss of cholesterol from the sperm plasma membrane, “hyperactiviation” = different motility patterns, capable of undergoing acrosome exocytosis.



gained through capacitation, different/faster motility problems needed to access egg. CatSper (short for cation channel of sperm) is a protein in the sperm membrane that regulates the hyperactivated sperm motility.


Lactobacilli, microbiome

microbes in the vagina and the collection of microbes respectively. A normal vaginal microbiome maintains vaginal health and prevents vaginal infections through a normal vaginal PH which is acidic (low PH.)



organelle that develops over the anterior half of the spermatazoa - like the cap on the sperm. The contents include surface antigens and numerous enzymes which are responsible for breaking through the egg's tough coating and allowing fertilization to occur.


Acrosome exocytosis (or acrosome reaction)

When Sperm interacts with Zona Pellucida --> acrosome exocytosis. Release of acrosome contents out of the sperm, via fusion of outer acrosomal membrane with the plasma membrane. Calcium is a key second messenger that induces the sperm to undergo acrosome exocytosis.


Egg activation

signal from the sperm triggers the egg-to-embryo transition - induces the egg to undergo the necessary physiological changes to become a one-cell-embryo (zygote). Calcium is also an important second messenger in the egg to trigger egg activation. Main results: 1. prevention of polyspermy 2. cell cycle resumption ie finishes meiosis and progresses to embryonic mitosis.


PLC ( PLCzeta )

A sperm specific PLC which generates IP3 in the sperm-egg cytoplasmic fusion. --> release of calcium necessary for egg activation


Cortical granules

small granules in the egg, just under the plasma membrane. Calcium increase induces exocytosis of the cortical granules. Cortical granules release enzymes that modify the components of the ZP, so that sperm can no longer bind the ZP on the fertilized egg → block polyspermy.



fertilization by more than one sperm. Egg activation blocks this from happening.



a one-cell embryo, reaches this stage after egg activation and completion of meiosis.



cell division for embryos (mitosis and cell division to two cell, four cell, eight cell stages.)



one cell of a multicellular embryo.



After compaction, the embryo is in the morula stage.



embryonic stage formed through the processes of compaction and cavitation. Blastocyst reaches uterus and if endometrium is ready, implantation occurs → post implantation development including the formation of the placenta. The blastocyst hatches from the zona pellucida in order to implant.


Compaction, cavitation

compaction is the first differentiation event in the embryo. During compaction the cells of the embryo bind tightly to each other, forming a compact sphere. Cavitation - the formation of a cavity in the embryo - along with additional cell divisions form the blastocyst.


Inner cell mass, trophoblast

the two cell types in the blastocyst.


Embryonic stem cell

the inner cell mass cells of the blastocyst can be isolated and cultured to perform stem cell research.


2 Steps egg's preparations for fertilization

(1) Egg changes location from ovary to oviduct following ovulation (release from ovarian follicle) and transits to top region (ampulla) of the oviduct. (2) Meiotic maturation to metaphase II


The sperm's preparations for fertilization (4 stages)

(1) Epididymal maturation - sperm change from the testis to the end of the epididymis, sperm mature during epididymal transfer and acquire motility and ability to undergo capacitation. (2) Mixture with seminal fluids - nutrients, mucus and buffering components (which neutralize the acidity of the vagina in order to pass through.) (3) Capacitation - the physiological changes in sperm that confer the capacity to fertilize an egg. Occurs in the female reproductive tract. (4) Storage in the female reproductive tract - sperm bind to the epithelial cells that line the oviduct. Sperm can live for several days in the female tract (this is why the timing of emergency contraception is important.)


Steps to Fertilization (4 stages)

(1) Sperm-cumulus interaction - ovulated egg is surrounded by cumulus cells embedded in an extracellular matrix. Sperm binds to and works through the matrix. Motility is necessary for the sperm to get through the layers of cumulus cells of to the zona pellucida. (2) Sperm-zona pellucida (ZP) interaction - the ZP is the egg coat composed of glycoproteins, ZP helps induce the sperm to undergo acrosomal exocytosis, where the acrosome releases enzymes that can help to digest a hole in the ZP. (3) Sperm-egg plasma membrane interactions - making one cell out of two by merging the membranes of the sperm and the egg. (4) Egg activation - signal from the sperm triggers the egg-to-embryo transition.