Capacitation, Acrosome Reaction, and Fertilization

Where do sperm have to be to acquire maximum fertility?

In the female reproductive tract

What is sperm capacitation?

Biochemical changes in plasma membrane important for removing de-capacitation factors

What is sperm capacitation crucial for?

Critical for sperm to be able to bind to the zona pellucida

What are decapcitation factors?

Proteins, glycolipids, and/or lipids

Where are sperm cells when decapacitation factors are added?

Epididymis

What does the removal of decapacitation factors do?

The removal of these factors and cholesterol destabilizes the plasma membrane

What does capacitation lead to?

Changes on outer acrosomal membrane and inner plasma membrane

How long does capacitation take?

1-6 hours

What is the result of capacitation?

Sperm that are compotent to undergo acrosome reaction if presented with the "right" stimulus

What is important about the process of capacitation?

It's reversible in vitro with a changed environment

What is seen after both capacitation and 12-24 hours in the isthmus?

Hyperactivitation where the sperm recharges in the isthmus and then has increase cAMP and power output

What are the steps post-capacitation, leading to fertilization?

Hyperactive motility, binding to zona pellucida, acrosomal reaction, penetration of zona pellucida, sperm-oocyte membrane fusion, sperm engulfed, oocyte activation, decondensation of sperm nucleus, formation of male and female pronucleus

What is the name of the space between the oocyte and zona pellucida?

Perivitelline space

What is the purpose of the zona or vitelline block?

To keep other sperm from entering the oocyte after oocyte activation

What are the three glycoproteins in the zona pellucida?

ZP-1, ZP-2, ZP-3

What is another name for the plasma membrane of the oocyte?

Oolemma

What is contained inside the 1st polar body of the oocyte?

The 2 copies of DNA that were previously extruded

What is caused by the binding of the sperm to the zona pellucida?

The acrosome reaction

What is the shape of the sperm head before the acrosome reaction?

Sperm head membranes are intact

What happens to the sperm head during the acrosome reaction?

The plasma membrane and outer acrosomal membrane are fused

What happens to the sperm head after the acrosome reaction?

The inner acrosomal membrane and equatorial segment are exposed

What is vesiculation?

- multiple fusion sites (acrosomal reaction) forming many small vesicles

What does ZP-3 do to the sperm?

Binds the sperm to the zona pellucida

What does ZP-2 do?

Anchors to the Zona Pellucida

What is the final step of the acrosome reaction?

The release of acrosin, which is the major enzyme permitting penetration through zona pellucida

What happens to the acrosome during penetration of the zona pellucida?

The acrosome swells and is lost

What initiates the acrosome reaction?

ZP3, which passes sperm off to ZP2 to be anchored to the zona pellucida

What pushes the sperm through the zona pellucida?

Mechanical force generated by the motile sperm

What does localized digestion of the zona pellucida do for the blastomere?

Helps maintain an intact zona pellucida, which may help to prevent the separation of the blastomere during early embryogenesis

What does fertilization require?

fusion of the equatorial segment and the oocyte plasma membrane

What does the sperm do to the oocyte once it enters?

Makes the oocyte resume meiosis

How often do sperm induced calcium oscillations occur?

Every 10-20 minutes

What happens during oocyte activation?

Completion of meiosis II (extrusion of the 2nd polar body - set of extra chromosomes = not needed)

What soluble sperm component induces calcium oscillations?

PLC

What do the cortical granules do during oocyte activation?

Migrate to the oocyte membrane to create a zona pellucida block

Where do the polyspermy blocks occur in mammals?

Zona pellucida

Where do the polyspermy blocks occur in invertebrates, amphibians, fish, and rabbits?

The perivitelline space

Where do the polyspermy blocks occur in amphibians and avians?

Inside the oocyte

What does the increase in calcium oscillations cause in MPF?

A decrease

What is an ootid?

The stage of fertilization where the oocyte contains both a male and female pronucleus

What does glutathione do?

Helps decondensation of paternal genetic material

What is syngamy?

fusion of male and female pronuclei

What is a zygote?

A diploid cell resulting after fusion of male and female pronuclei