Pros of abortion essay

Saunders, This cell results from the union of an oocyte and a sperm during fertilization. A zygote is the beginning of a new human being i. By Jan E. Parthenon Publishing Group, By Frank J. Harwood Academic Publishers, By Timothy B. Erickson and others. McGraw-Hill, By William F. McGraw Hill, The expert help of the Editorial Committee [of Contributing Scientists] has enabled us to formulate definitions and explanations that correspond to recent findings of scientists working in their various disciplines.

Precise editorial review in the offices of the publisher has contributed to a standard of excellence. This is a dictionary of the basic terms of the physical and the biological sciences. The compiling of a specialized dictionary is, perhaps more than in most other reference books, the result of many scholars and editors working together.

We are fortunate to have an outstanding group of active scientists, who read, commented upon and corrected the entire manuscript, and we are indented to them for their thorough work.


By Marjorie A. Year Book Medical Publishers, They use this date to define a menstrual age stretching from time 0, which is usually 14 days before fertilization…. Thieme, However, sperm deposited in the reproductive tract up to 6 days prior to ovulation can survive to fertilize oocytes. Thus, most pregnancies occur when sexual intercourse occurs within a 6-day period that ends on the day of ovulation.

By Robert Kail and John Cavanaugh. Cengage Learning, Fertilization begins the period of the zygote, the technical term for the fertilized egg. This period ends when the zygote implants itself in the wall of the uterus see Figure 2. During these two weeks, the zygote grows rapidly though cell division see Figure 2. The zygote travels down the Fallopian tube toward the uterus and divides for the first time; it then continues to do so every 12 hours.

Edited by David K. Springer, Concomitantly with the distinct changes in physiology that occur during development from the zygote to the blastocyst stage are dynamic changes in the metabolism of the embryo.

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At the zygote stage, the embryo is initially quiescent with a low metabolic and biosynthetic activity. At these early stages, the embryo predominantly uses the carboxylic acids pyruvate and lactate as its preferred energy substrates.

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However, the embryo does take up low levels of glucose, 14, 15 which are likely metabolized by the pentose-phosphate pathway for the maintenance of reducing power in the cell particularly in the production of reduced glutathione for protection against oxidative stress. Furthermore, there is a recent understanding that the metabolism of glucose by the hexosamine biosynthesis pathway in the early embryo may be important in establishing O-linked glycosylation that is important for later stage development.

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Human Reproduction Update , May Embryo-derived paf [platelet-activating factor] … is produced by de novo synthesis. This synthesis commences soon after fertilization and persists throughout the preimplantation phase.

In vitro, supplementation of culture media with paf improves embryo development. It was subsequently shown that paf stimulated embryo metabolism Ryan et al.

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Insulin Wales et al. The possibility that a range of trophic factors may act on the early embryo was suggested by the detection of mRNA for a range of peptide growth factor ligands and their corresponding receptors Rappolee et al. Since these observations, many putative autocrine, paracrine and endocrine factors have been implicated in supporting preimplantation embryo development Kane et al.

Blackwell, The genotype is determined at fertilization when genetic information from the egg and sperm is combined. The zygote contains a new combination of chromosomes that is different from that in the cells of either of the parents.


This mechanism forms the basis of biparental inheritance and variation of the human species. By Francisco J. Benjamin Cummings Publishing Company, If we assume there are 30, structural gene loci in a human being, which may be an underestimate, a person will be heterozygous at 30, X 0. By Richard E. Academic Press, NOTE: The above calculation only accounts for the genetic variation of the female. Therefore, the odds against a woman conceiving the same pre-birth human twice with or without the same mate are actually much higher than this.

By John F. By Alan Guth. Helix Books, By Richard Feynman. Basic Books, The three basic types are protons, neutrons, and electrons. Each atom has a definite number of these subatomic particles. NOTE: As shown above, all atoms contain at least one baryon, and thus 10 80 represents a rough maximum for the number of atoms in the visible universe.

Biochemical Journal , May 15, Epigenetic modifications can, therefore, cause phenotypic variation in the absence of genetic differences. By Geraldine Lux Flanagan. It is one-tenth of an inch long; the heart begins to beat; the brain has two lobes; the early spinal cord is bordered by the future vertebrae and muscle segments.

Churchill Livingstone, The cranial half of the groove, representing developing brain, begins to develop a cephalic flexure, optic primordia become visible and early head and tail folds have appeared, as Stage 10 is approached. By Vernon L. Jones and Bartlett, Occupying days 21—23, 23—25, 25—27 respectively, … primary cerebral vesicles appear. The primordia of the thyroid gland, lungs, liver, pancreas, and mesonephric tubules are all identifiable. Roughly equivalent to the 6th and 7th weeks …. The pontine flexure, cerebral hemispheres and cerebellum are developing.

Simon and Shuster, In the sixth and seventh weeks, nerves and muscles work together for the first time. If the area of the lips, the first to become sensitive to touch, is gently stroked, the baby, who then is still an embryo, responds by bending the upper body to one side and making a quick backward motion with the arms. NOTE: The details above are documented by photos. Copyright: Life Issues.

Pro and anti-abortion rights activists on future of Alabama abortion bill

NOTE: A number of different photographers have published intrauterine photos. Just Facts asked several of these individuals for permission to reproduce their pictures, and Life Issues was the only one who consented. The pictures from Life Issues look similar to those taken by the other photographers. This criterion was chosen by embryologists because the beginning bone formation coincides with the essential completion of the body.

Encyclopedia of Human Biology Volume 3. Division of the heart into chambers is complete, and a definitive vascular system carries blood to and from all body parts. All components of the brain and the spinal cord are formed, and nerves link the stem of the brain and the spinal cord to all tissues and organs of the body.

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  6. Attempts to suckle have been seen in utero and in aborted fetuses of 3 months. Reflexes that develop during the third month involve the mouth and the head …. Electrical activity of the nervous system is discernible at the same time, but periods of electrical silence can occur up to midterm. By Ricki Lewis. This falls under the category of 15 weeks after LMP and 13 weeks after fertilization. By Ronald W. New England Journal of Medicine , November 19, Cutaneous sensory receptors appear in the perioral [mouth] area of the human fetus in the 7th week of gestation; they spread to the rest of the face, the palms of the hands and the soles of the feet by the 11th week, to the trunk and proximal parts of the arms and legs by the 15th week, and to all cutaneous and mucous surfaces by the 20th week.

    Development of the fetal neocortex begins at 8 weeks of gestation, and by 20 weeks each cortex has a full complement of 10 9 neurons. NOTE: This article uses the obstetric method of counting from the last menstrual period as evidenced by the chart on page , which uses a gestation of 40 weeks for pregnancy.

    Pros of abortion