MCQ. Once an egg cell has been fertilized, it prevents other sperm cells from reaching it by changing?
Once an egg cell has been fertilized, it prevents other sperm cells from reaching it by changing A) their motility. B) the pH in the vagina. C) the number of tight junctions between the granulosa cells that surround it. D) the viscosity of its zona pellucida. E) its location.
How does the sperm know which fallopian tubes to swim up to fertilsw the egg?
Sperm can't actually think, they're just single-celled organisms doing what nature has programmed them to do... which is wiggle frantically to "swim" in whatever direction they happen to be facing. It's pure random luck which sperm finds the egg. That's why each ejaculation contains millions of the little guys, since nature expects most of them to fail. As for your second question, and egg only "lives" about 6-24 hours, so if it dies before being exposed to sperm, then it won't get fertilized. Or if it does get fertilized but there was something nonviable with either the egg or sperm that reached it, the cells will stop dividing and it will die. Or, the egg might even make it to implantation, but it might take too long to get there before your period starts, or there again may be something wrong with the conception and it will end in an early miscarriage (about 30% of pregnancies do). And that's why you only have about a 20-30% chance of getting pregnant any given cycle. Nature isn't perfect with this stuff... far from it!
How does Cu act as a spermicide?
Copper ions destroy biochemical structures with ease — they confound enzyme structures, making them useless. The ions can also bore holes into cell membranes, by interacting with the cells lipidbilayer, spilling the contents of the cell into the surrounding environment.Once a Copper T is in place, copper ions separate from the coiled copper wire and begin to alter the biochemistry around the uterus. "Alter" sounds like a strong and permanent word, but it really isn't. The copper ions leach into uterine fluids and the cervical mucus — when these fluids come in contact with sperm, the copper ions sound the death knell for the squiggly beasts.Copper ions prevent pregnancy by inhibiting the movement of sperm, because the copper-ion-containing fluids are directly toxic to sperm. Even if an aggressive little spermatozoa fertilizes an egg, the copper ion laden environment prevents implantation of the fertilized egg, and thus pregnancy.
Can sperm be manually extracted from a male that has had a vasectomy and used to produce a child via in vitro fertilization?
A technique exists whereby they use a hollow needle to suck sperm cells directly from the testicles. If the man was normally fertile before the vasectomy then the chance is very good to obtain live sperm cells.The amount is too little for a normal insemination, so a fertility treatment called ICSI would be needed to cause a pregnancy.The chances for a succesfull pregnancy with this are in general higher then when trying to reverse the vasectomy with an operation. Additional benefit is that no 2nd vasectomy is needed once the childwish has been adressed.
How or does Astaxanthin affect testosterone?
Astaxanthin may help to naturally modulate the levels and activities of testosterone, estrogen (E) and certain other hormones. Natural astaxanthin is known as a strong antioxidant and anti-inflammatory. It also demonstrates certain other medical potentials.Improvement of blood circulation and better endothelial function leading to relaxed blood vessels and lowered blood pressure - thanks to astaxanthin supplements, have been instrumental in inhibiting the build up arterial plaque on the walls of blood vessels. Astaxanthin for blood pressure not only leads to better cardio vascular health, it also plays a vital role in preventing atherosclerosis, heart attacks and brain stroke, by maintaining the blood circulation at optimum levels. Astaxanthin supplements hold promise for couples unable to conceive a baby as these supplements are known to improve sperm count and sperm quality. Sperm mobility and the fertility potential of the sperm is enhanced greatly by the anti-oxidant properties of astaxanthin.
How does drugs like norethindrone and nonestradiol control birth ?
Combined contraceptive pills act by inhibiting ovulation which occurs during midcycle.Progesterone and estrogen in pills act by negative feedback on hypothalamus pituitary ovarian axis.They inhibit pulsatile release of GnRh From Hypothalamus, which in turn inhibits release of FSH and LH from Pituitary ,which are responsible for follicular development and ovulation respectively.When ovulation is inhibited fertization doesn't occur.Progesterone also acts by causing changes in endometrium which causes it to become hostile for nidation and also causes cervical mucus to become more viscous so as to make it difficult for sperm penetration.There are 2 types of OC pills.Combined and POP pills ie progesterone only pills.
Is someone out there good at Biology (reproduction)?
1. Secretions of fructose for energy help the sperm to be motile. 2. FSH (follical stimulating hormone) & LH (Leutinising hormone) 3. Estrogen inhibits LH secretion 4. Negative feedback - LH cause leutinisation of cells which produce Estrogen which inhibits LH production 5. Positive feedback - When estrogen reaches a certain level of concentration it switches from inhibiting LH production to encouraging - this causes a rapid LH surge and as the LH increases estrogen decreases again until is falls below that switching concentration and again inhibits LH causing its to decrease once again. Thus there is a short and sharp increase followed by the short and sharp decrease in LH
How does the pregnancy prevention pill Postinor-2 work?
The active ingredient in Postinor-2 is levongesterol [1].Levonorgestrel is in a class of medications called progestins. It works by preventing the release of an egg from the ovary or preventing fertilization of the egg by sperm (male reproductive cells). It also may work by changing the lining of the uterus (womb) to prevent development of a pregnancy.[2]“Postinor-2 is an emergency contraceptive only. Postinor-2 is not intended as a regular method of contraception. It is used to prevent pregnancy when taken within 72 hours of unprotected intercourse. It is estimated that Postinor-2 will prevent 85% of expected pregnancies. 95% of expected pregnancies will be prevented if taken within the first 24 hours, declining to 58% if taken between 48 hours and 72 hours after unprotected intercourse.” [3]This video explains how Postinor-2 works (see below for a written explanation):In order to get pregnant, an ovulated egg (female reproductive cell) must travel from the ovary, down the fallopian tube where it is usually fertilized by a sperm cell (male reproductive cell). After fertilization, it implants in the walls of the uterus and a pregnancy occurs.In order for ovulation to take place, the hormone LH surges, signaling to the ovary to release an egg. Postinor-2 inhibits the LH surge so that ovulation doesn’t take place [4]. However, if ovulation is imminent, taking the pill will not have any effect and ovulation will occur [5]. Should ovulation have already taken place, then Postinor-2 may work to prevent fertilization of the egg. One study found that levonogesterol (the main ingredient in Postinor-2) increasesintrauterine concentrations of glycodelin at the time of ovulation; since glycodelin inhibits fertilization, this result may indicate an additional mechanism of action [for pregnancy prevention] when ovulation is not inhibited. [6]For more, see: Update on Emergency Contraception, WHO Emergency contraception, FAQ - Postinor Morning After PillFootnotes[1] Postinor-2 Tablets[2] Levonorgestrel: MedlinePlus Drug Information[3] Postinor-2 Tablets[4] Emergency contraception: how does it work?[5] Update on Emergency Contraception[6] http://ec.princeton.edu/question...