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33 Cards in this Set

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What is the difference between spermatogenesis & spermiogenesis?
Spermatogenesis includes mitosis, meiosis I, & meiosis II. Takes sperm from spermatogonium to early spermatids. Spermiogenesis takes early spermatids to late spermatids to spermatozoa.
Where does the maturation of sperm occur?
Seminiferous tubules
Describe the location of steps of sperm maturation.
Spermatogonium are at the edges & sperm mature as they move to the center.
What are sperm called after each phase of maturation: mitosis, meiosis I, meiosis II, through final maturation.
Mitosis: Spermatogonium.
Meiosis I: 1y spermatocyte
Meiosis II: 2y spermatocyte
Spermiogenesis: Early spermatid, Late spermatid, Spermatozoa
What is the corona radiata & how do sperm get through it?
Corona radiata is granulosa cells & ECM w/ hyaluronic H+. Sperm get through it using hyaluronidase & active swimming.
What are the 5 steps of fertilization?
Penetration of corona radiata, zona binding, acrosome rxn, zona penetration, & sperm-egg fusion
How is zona binding achieved?
Receptor on sperm (SED1) binds to ligand on zona pellucida (ZP3)
What is the acrosome?
Organelle/cap over the anterior half of the spermatozoa's head which contains digestive nZ including hyaluronidase & acrosin
What is the acrosome reaction & what is essential for it to be successful?
Occurs as the sperm approaches the egg. Membrane surrounding the acrosome fuses w/ the PM of the sperm, exposing the contents of the acrosome & making the sperm capable of fusing w/ the egg. Ion txpt of Ca2+ is essential for this to occur.
What is the consequence of the acrosome reaction?
Zona penetration & the ability of the sperm to bind with & penetrate the plasma membrane (exposes dis-integrin to bind to & break up integrin in PM)
How is plasma membrane binding & fusion achieved?
Via specific receptors, integrin & fertilin
How is polyspermy prevented?
Through the zona rxn. After fusion of the oocyte w/ the spermatozoa, there is a Ca2+ wave across the egg. Cortical granules fuse w/ egg PM, releasing their contents, making the zona pellucida refractory to sperm binding (so additional sperm can't enter) and hardening the ZP so sperm that have started but not finished transversing it are stopped. The egg surface also changes.
Fertilized egg
After the zona rxn, what occurs next? (up to mitotic spindle formation)
Increase in egg metabolism. Decondensation of sperm nucleus (the male pronucleus). Oocyte meiosis is completed. The pronuclei approach, nuclear membranes breakdown, & they fuse, forming the zygote and the mitotic spindle is formed.
In cleavage, equivalent cell division occurs up to the __ stage, where you get the first appearance of nonequivalent cells.
What are the 2 steps after the morula stage?
Cavitation & blastocyst formation
What happens during blastocyst formation?
Formation of the inner cell mass & trophoblast
What are dizygotic twins?
2 eggs fertilized by 2 sperm
What are 3 ways that monozygotic twinning is achieved?
1. Egg splits -> 2 babies, 2 placenta, 2 amniotic sacs
2. ICM splits -> 2 babies, 2 placenta, 2 amniotic sacs
3. ICM splits incompletely -> Conjoined babies, 2 placenta, 1 amniotic sac
At how many days after fertilization does blastocyst formation & hatching occur?
Day 4-5
How does the blastocyst prepare for implantation?
Hatching from the zona pellucida via proteolytic mechanisms (perhaps attributable to the trophoblast??)
When does attachment occur?
Day 5-6
What is blastocyst attachment? What is required? What is it mediated by?
Interaction between trophoblast & uterine epithelium, preventing easy flushing of the blastocyst from the uterus; Requires uterine receptivity; Mediated by integrins & selectins
What state must the uterus be in for attachment to occur?
Progestagenic state, plus estrogen
What uterine surface changes are necessary for blastocyst attachment?
Pinopodes (markers on epithelial cells); Reduced mucins & negative charge
In addition to creating surface changes to the epithelium, why else is estrogen required for attachment?
Causes endometrial cells to produce LIF, which is critical for implantation; Acts on blastocyst & stroma
While LIF is globally upregulated, __ appears only in uterine epithelial cells adjacent to the blastocyst and precedes zona pellucida dissolution.
How does HB-EGF facilitate blastocyst attachment?
There are receptors on the blastocyst for HB & EGF, providing double binding sites. Binding is followed by dissolution of the zona pellucida & trophoblast invasion.
What 2 other factors are required for adhesion?
Integrins & Selectins
Describe the process of blastocyst invasion.
Trophoblast differentiates into 2 layers (cytotrophoblast around outside; syncytiotrophoblast (outer layer) is highly invasive and starts to penetrate into endometrium), Cellular projections insert between uterine epithelial cells, Proteases secreted by the trophoblast penetrate the uterine epithelium & matrix
What is the stromal response to invasion?
Decidualization & TGF-beta
What does the TGF-beta do?
Slows invasion & promotes angiogenesis
List 6 abnormal implantation sites.
Fallopian tube, Ovary, Intestine, Intestinal mesentery, Internal Os, Cervix