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Regards the site.FERTILIZATION
Upon penetration by the sperm-stage four of oogenesis the ovum is considered to be mature. The entrance of the sperm into the ovum causes an immediate change in the peripheral layer of the egg, a yolk-originated membrane that prevents other sperm from penetrating it. When it enters the egg, the fertilizing sperm loses its tail, and its head and the connecting piece (neck) expand and grow into the male pronucleus and centrosome (important protoplasmic body in subsequent cell division). At this point, the female pronucleus (nucleus of the secondary oocyte) and the male pronucleus (head of the spermatozoon) approach each other, the nuclear membranes disappear, and the gene-carrying portions (chromatin) of the two nuclei join, then reform into two groups of equal number. Fertilization is now complete.
There are three general terms used to describe the fertilized ovum as it develops into the infant we know at birth. From the time of fertilization until the second week, the developing cell mass is referred to as a zygote; from the second to the eighth week, it is called an embryo; and from the eighth week until birth, a fetus. The appearance and initial development of all the rudimentary systems of the body mark the end of the embryonic period. The last period, the fetal stage, consists of the further growth and elaboration of existing rudimentary systems.
The process of parthenogenesis as described by Professor E. H. Herrick might be mentioned here. Also called "virgin birth," parthenogenesis concerns the "fertilization" and development of the female's egg without any possible previous contact with spermatozoa. This phenomenon is a common occurrence in lower animals, such as the honeybee, and is the sole method of reproduction among certain other insects. Experimentation in parthenogenesis with various animals has shown that a great number of stimuli will induce the process of development as if the egg had been fertilized in the usual manner. For example, cooling the Fallopian tubes of rabbits, heating the eggs of certain moths, and even applying saliva of human males to carp eggs have sufficiently irritated the eggs to prompt their development.1""'854 A very high percentage of the eggs of virgin turkey hens undergo parthenogenesis in experimental circumstances, although the early death rate among the hatched birds is very high.
The obvious question arises: is this phenomenon possible in human beings? There is no definite answer to the question at the present time, and there is considerable disagreement among investigators, past and present. One aspect is a certainty, however. If parthenogenesis were to occur, the offspring must invariably be female because of the way chromosomes are arranged in men and women. Since women have only one type of sex-determining chromosome (X), only the X chromosome could be passed on.
One of the leading researchers in the field of fertilization is Dr. Landrum B. Shettles. In a study of 400 human ova, he observed that the first stages of developmental processes had begun in three of the eggs, even though there could have been no contact with sperm. The logical conclusion would seem to be that if developmental processes in the human ovum can begin spontaneously, they should be able to continue to term.10" Only further research can uncover the answer.
The phrase "virgin birth" ordinarily conveys the idea of human pregnancy and subsequent birth without a previous act of sexual intercourse followed by union of ovum and sperm. In this context, the possibility of a true virgin birth has never been scientifically established. Impregnation without penile penetration, however, is a real possibility, and it is a phenomenon that happens more often than many realize. If, for instance, a man were to have his penis near or on a woman's vulva and ejaculate during sexual play, semen could enter the vaginal opening and make its way through the vagina into the uterus. Or if a man were to ejaculate, get sperm on his hands, and soon thereafter manually manipulate the woman's genitals, especially if he inserted a finger into the vagina, he could introduce sperm into the vaginal canal. Were impregnation to result in either of these instances, and the girl's hymen was still intact, the subsequent parturition might accurately be called a "virgin birth."
The fertilized ovum produces two daughter cells by its first mitotic division. Each daughter cell receives one-half the chromosomes contained in both the sperm and ovum. The fertilized ovum in its early stage, as was stated previously, is referred to as a zygote.
The process of cell division in the zygote is known as segmentation. The spherical zygote undergoes mitotic divisions, forming first two cells, then four by a cleavage at right angles to the first, then into eight by yet another cleavage in a third plane. These divisions create four cells above the original cleavage and four below. The eight cells are further divided by a similar process into sixteen, then into thirty-two, and so on. The increasing number of cells develops within the fixed outer bounds of the zygote, the outer dimensions remaining the same until implantation.
Through the process of mitotic division, the fertilized ovum or zygote develops into a spherical mass of cells known as a morula. The morula moves slowly through the uterine tubes and into the uterus; during this process a cavity is developed within it. The cavity enlarges until there is an outer hollow sphere of cells, the trophoblast, from which the inner cell layer projects toward the center. At this stage the fertilized egg is referred to as a blastocyst
The inner ball of cells forms two layers, the ectoderm and the endoderm, in such a manner that two cavities take shape simultaneously. Later, a third cellular layer, the mesoderm, makes its appearance between the ectoderm and the endoderm. These three layers of primitive germ cells, which are situated between the two cavities, constitute the embryonic disc, from which the embryo proper develops.
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Pharmacy Information
SEXUALITY DEFINED: PAGAN-POLYTHEISTIC INFLUENCES - ROMAN SEXUALITY
Although there is reasonable agreement among most authorities regarding the characteristics of Greek sexuality, Roman customs and values are a matter of considerable debate. Conventional wisdom holds that the Roman society was as sexually promiscuous as the Greek; and it is popularly believed that the collapse of the Roman Empire was due, in no small part, to the sexual excesses of its citizens (Canter, 1963). These views have been challenged, however, on the grounds that the sexual excesses of Roman society have been greatly exaggerated and that the accounts of these events are biased and inaccurate (Bullough, 1976). Whatever the actual case, certainly Roman culture was more complicated and multidimensional than Greek society. The Roman Empire endured for a relatively long period of time; and, whereas the Greeks retained their beliefs and customs, Roman culture changed in the light of the changing empire and in the face of continuous exposure to other cultures.
The Romans, of course, shared the polytheistic religion of the Greeks, as well as the sexuality of their deities. Thus, they shared the Grecian religious approval of sex. As Grimal states:
To love was to obey the gods and achieve one of the requisites of the human condition. Chastity could be required by religious rites in certain cases, but it was not a good thing in itself; not even a desirable thing; it was rather an impairment of what was good and desirable for among the gifts of the gods to man, love is always to be found. [Grimal, 1967, p. xiii]
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