Gamete Transport and Fertilization Flashcards
What is the major barrier for sperm to travel in the female reproductive tract?
the cervix
What is the ‘privelaged’ pathway through the cervix?
the vast majority of viable sperm are delivered by sustained transport mechanisms that move the sperm to the uterus in a uniform pattern over time
What mechanisms cause sperm to be inactivated or lost?
retrograde transport, phagocytosis, or microbes that are introduced during copulation
What is bidirectional myometiral contractility?
when contractions move towards the ovary during insemination and move towards the vagina during mensturation and perturition
What is the direction of bidirectional myometrial contractility determined by?
actin:myosin ratio and the type of myosin present
What is sperm capacitation?
a process where the zona pellucida binding proteins and chemotaxis receptors on the acrosome of the sperm are revealed
What are the steps of the fertilization process from attachment to syngamy?
(a) sperm attaches to the ZP, (b) a sperm acrosome binds to receptors on ZP, (c) acrosome reaction, (d) penetration of a sperm into ZP, (e) fusion of a sperm with the plasma (vitelline) membrane of the oocyte (f) cortical reaction releases calcium across the perivitelline space to the ZP (g) the zona reaction that biochemically alters the ZP to make it impervious to other sperm (h) introduction of sperm DNA into the oocyte
How does the sperm attach to the zona pellucida?
acrosomal receptors attract the sperm to the zona pellucida and thenn acrosomal enzymes break apart proteins on the corona radiata to allow it to attach
How does the sperm bind to the receptors on the zona pellucida?
the acrosome surface contains moleculaes (ZBR and ARPR) that physically bind to a molecule (ZP3) on the zona pelucida
What is the acrosome reactin initiated by?
the ZBR-ZP3 binding event
During fusion, where does the sperm go?
it transverses the zona pellucida and settles into the perivitelline space
What does the fusion of the inner acrosomal membrane and the oocyte membrane cause?
the release of calcium from cortical granules initiating the zona reaction
How does the sperm introduce its DNA into the oocyte?
it decondenses (uses the reduction of disulfide linkages in the histone proteins holding the DNA)from its supercoiled state to a more linear state
What is blastogenesis?
when trophoplasts release Na that osmotically attracts water thus pushing the central blastomeres eccentrically into the intracellular mass
Why do outer blastomeres of the morula adhere?
because of tight junctions between the cells
