Exam 5 Review:  Chapter 28 Fertilization

pregnancy = gestation - The period from conception to birth when a woman carries a developing embryo/fetus in her uterus after the ferilization of her ovum by a spermatozoan; it is a period of positive feedback regulation in which the autonomic nervous system and various hormones, especially follicle stimulating hormone =FSH, luteinizing hormone = LH, prolactin, estrogens, progesterone, human chorionic gonadotropin = HCG, and relaxin, regulate and support the physiological processes which provide support and nutrition to the developing embryo/fetus in the uterus and ready the mammary glands for milk production.  [Male Pregnancy?  No, its an urban legend spoof.  Here's how the spoof may have gotten started:  Professor Robert Winston.]

fertilization - The act or process of initiating biological reproduction by insemination which achieves the union of male and female gametes to form a zygote; in the human, a secondary oocyte, once ovulated, can remain viable for 12 to 24 hours; sperm can remain fertile in the female reproductive tract for 12 to 48 hours, although some may last for 72 hours; for fertilization to take place, intercourse can take place from 72 hours before to 24 hours after ovulation.

acrosome - The membrane bound vesicle at the tip of the head of the sperm which contains proteolytic enzymes, e.g., hyaluronidase, which have the capacity to digest the outer coat of the egg = ovum to allow the sperm to inject its haploid sperm nucleus into the egg = ovum at fertilization.

acrosomal reaction - The release of proteolytic enzymes from the specialized anterior vacuole (acrosome) at the tip of the sperm head which is triggered by reaction with glycoproteins of the egg's zona pellucida; these proteolytic enzymes, e.g., hyaluronidase, have the capacity to digest the outer coat of the egg = ovum to allow the sperm to inject its haploid sperm nucleus into the egg = ovum at fertilization.

cortical reaction - The activation response of the ovum to the acrosomal reaction and subsequent penetration of the haploid sperm nucleus into the egg = ovum at fertilization; this gradual biochemical reaction prevents polyspermy in two stages: (1) the fast block is a wave of depolarization which spreads across the egg = ovum cell membrane due to the opening of ion channels including calcium channels; and (2) the slow block is the response to second messenger calcium ions which activate cortical granules to release their contents beneath the egg = ovum cell membrane to form a physical barrier to prevent entry of any additional sperm nuclei into the the egg = ovum cytoplasm.

capacitation - The physiological process which occurs in the female genital tract after exposure to regulatory substances which modify the sperm head and acrosome membranes, and which causes spermatozoas to undergo the physical and biochemical changes necessary to penetrate and fertilize an egg = ovum.  [You-Tube has an animation on sperm capacitation.]

corona radiata - The single layer of low columnar granulosa, i.e., follicular, cells of the secondary and vesicular ovarian follicles which surround and anchor the the diploid primary oocyte to the inner follicular wall.

zona pellucida - The thick, solid, transparent outer membrane of glycoproteins. immediately external to the oocyte's cell membrane, separating the developing oocyte from the granulosa, i.e., follicular, cells of the primary, secondary, and vesicular follicles (the cells which will form the corona radiata); after ovulation, it forms a physical barrier through which sperm must penetrate in order to achieve fertilization; the acrosomal proteolytic enzymes of the sperm head can digest the glycoproteins of the zona pellucida.

syngamy - The cellular act of sexual reproduction in which two gametes, egg = ovum and spermatozoan unite or fuse to achieve fertilization, the formation of the fertilized egg = zygote.

polyspermy - The inappropriate entry of several sperm into one ovum during fertilization; many mechanisms are in place to prevent it, since the outcome of the formation of a defective polyploid embryo is always the failure to survive to birth.

pronucleus - The haploid nucleus of a spermatozoan or egg = ovum before fusion (syngamy) of the nuclei in fertilization; the use of this term is restricted to the time after the spermatozoan's pronucleus has entered the ovum at the instance of fertilization but before its fusion with the female pronucleus.

zygote - The single diploid cell formed by the successful union (syngamy) of two gametes, sperm and egg, during reproduction before cleavage begins; the especially a fertilized ovum or egg.

dizygotic twins - The scientific term for nonidentical twins who developed from two separate fertilized eggs; they share, on average, only 25% of their genes; they occur in approximately one of every 250 births in the US. aka - fraternal twins.

monozygotic twins  - The scientific term for identical twins who developed from a single fertilized egg which broke into two parts during early cleavage; such individuals share 100% of their genes; they occur in approximately one of every 170 births in the US. aka - fraternal twins.

conjoined twins - Identical twins born with their bodies joined at some point and having varying degrees of residual duplication, a result of the incomplete division of the ovum from which the twins developed.  aka - diplosomia; politically incorrect nickname - Siamese twins.

[For further information on twins, visit "Twins:  A Parents' Guide," and "Links to Twin Studies," and "The Institute for Behavioral Genetics Twin Studies."  A quick web search will reveal many more such sites.]

in vitro fertilization (IVF) - Medical procedures which attempt the fertilization of an egg in a laboratory dish or test tube; specifically : mixture, usually in a laboratory dish, of sperm with eggs which have been surgically removed from an ovary, which is followed by implantation of one or more of the resulting fertilized eggs into a female's uterus.

On July 25th, 1978, Drs. Robert Edwards and Patrick Steptoe deliver the world’s first test tube baby. Louise Brown is the daughter of Lesley and John, a couple from Bristol, England, who have been trying to conceive for nine years.

On December 28, 1981, Elizabeth Jordan Carr was born in Norfolk, VA, to a woman who had no fallopian tubes. Elizabeth Jordan Carr [in 2002], America’s first test tube baby, now 21 and a senior at Simmons College, embraces her birth delivery doctor Fredrick Wirth of King Prussia during a reunion in Boston on Tuesday. Dr Wirth delivered Carr 21 years ago in Norfolk.  — AP\PTI

embryo transfer = embryo transplant - After artificial insemination, the  process in which an egg that has been fertilized in vitro is transferred at the blastocyst stage into a recipient's uterus.

gamete intrafallopian transfer (GIFT) - A technique of assisted reproduction in cases of infertility in which eggs are obtained from an ovary, mixed with sperm, and inserted into a fallopian tube by a laparoscope.

After the retrieval of the eggs from the ovary, both sperm and eggs are injected through the catheter directly into the fallopian tube. Fertilization may then take place normally in the Fallopian tubes.

 1.