HUMAN EMBRYOLOGY

The human ovum, fertilized high in a fallopian tube, is brushed by the hairlike cilia in the tube toward the uterus, where it becomes implanted, that is, attached to and enclosed by decidual tissue of the uterine lining. Studies of primate embryos indicate that, in humans as well as in apes, cell multiplication begins during the journey of the ovum through the tube. The implanted embryo consists of a hollow sphere, the blastocyst, containing a mass of cells, called the embryonic mass, attached by a stalk to one side of the encircling membrane. In a blastocyst less than two weeks old and measuring 1 mm (0.04 in) in diameter, the microscope reveals the amnion (a sac surrounding the embryo), chorion (a membrane that develops around the amnion and lines the uterine wall), yolk sac, and distinct germ layers.

In the third week a closed tube appears in which the brain and spinal cord are to develop. Another tube, folding on itself, is developing into the heart, and at about this stage a portion of the minute yolk sac is enclosed in the body of the embryo to form a part of the embryonic alimentary canal. At the beginning of its fourth week the embryo, now about 4 to 5 mm (about 0.16 to 0.2 in) long, has the rudiments of eyes and ears, and each side of the neck shows four gill clefts. A tail is also present.

Early in the second month the buds of the arms and legs appear. The major internal organs begin to take shape, and in about the sixth week bones and muscles begin to form. By the third month the embryo is recognizable as that of a primate, and is now called a fetus. It has a definite face, with the mouth and nostrils distinct, and the external ears are forming. By the end of the eighth week the tail has usually been incorporated in the body, and in the 11th or 12th week the external genitals become evident. The human embryo is especially vulnerable to the damaging effects of X rays, of disease viruses such as measles, and of certain drugs during the fourth to the eighth week of gestation. These agents can result in the death of the embryo or in the birth of a child with deformed limbs or other abnormalities. By the fourth month an embryo has developed obvious human features. For development in the fetal stage, see Fetus. For abnormalities due to anomalous development, see Birth Defects. See alsoDevelopment; Multiple Birth; Obstetrics.

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HUMAN EMBRYOLOGY

The human ovum, fertilized high in a fallopian tube, is brushed by the hairlike cilia in the tube toward the uterus, where it becomes implanted, that is, attached to and enclosed by decidual tissue of the uterine lining. Studies of primate embryos indicate that, in humans as well as in apes, cell multiplication begins during the journey of the ovum through the tube. The implanted embryo consists of a hollow sphere, the blastocyst, containing a mass of cells, called the embryonic mass, attached by a stalk to one side of the encircling membrane. In a blastocyst less than two weeks old and measuring 1 mm (0.04 in) in diameter, the microscope reveals the amnion (a sac surrounding the embryo), chorion (a membrane that develops around the amnion and lines the uterine wall), yolk sac, and distinct germ layers.

In the third week a closed tube appears in which the brain and spinal cord are to develop. Another tube, folding on itself, is developing into the heart, and at about this stage a portion of the minute yolk sac is enclosed in the body of the embryo to form a part of the embryonic alimentary canal. At the beginning of its fourth week the embryo, now about 4 to 5 mm (about 0.16 to 0.2 in) long, has the rudiments of eyes and ears, and each side of the neck shows four gill clefts. A tail is also present.

Early in the second month the buds of the arms and legs appear. The major internal organs begin to take shape, and in about the sixth week bones and muscles begin to form. By the third month the embryo is recognizable as that of a primate, and is now called a fetus. It has a definite face, with the mouth and nostrils distinct, and the external ears are forming. By the end of the eighth week the tail has usually been incorporated in the body, and in the 11th or 12th week the external genitals become evident. The human embryo is especially vulnerable to the damaging effects of X rays, of disease viruses such as measles, and of certain drugs during the fourth to the eighth week of gestation. These agents can result in the death of the embryo or in the birth of a child with deformed limbs or other abnormalities. By the fourth month an embryo has developed obvious human features. For development in the fetal stage, see Fetus. For abnormalities due to anomalous development, see Birth Defects. See alsoDevelopment; Multiple Birth; Obstetrics.

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HUMAN EMBRYOLOGY

The human ovum, fertilized high in a fallopian tube, is brushed by the hairlike cilia in the tube toward the uterus, where it becomes implanted, that is, attached to and enclosed by decidual tissue of the uterine lining. Studies of primate embryos indicate that, in humans as well as in apes, cell multiplication begins during the journey of the ovum through the tube. The implanted embryo consists of a hollow sphere, the blastocyst, containing a mass of cells, called the embryonic mass, attached by a stalk to one side of the encircling membrane. In a blastocyst less than two weeks old and measuring 1 mm (0.04 in) in diameter, the microscope reveals the amnion (a sac surrounding the embryo), chorion (a membrane that develops around the amnion and lines the uterine wall), yolk sac, and distinct germ layers.

	Developing Embryo's First Month

	Developing Embryo's First Month Thirty hours after conception, the fertilized egg undergoes its first cell division. The embryo, as it is now called, continues to divide as it travels down the fallopian tube. It implants in the uterine lining approximately six days after fertilization, a ball of cells with a disk-shaped embryonic mass. In the second week, the placenta begins to form, nourishing an embryo now composed of the three primary types of tissue: endoderm, ectoderm, and mesoderm. The third week sees the formation of the neural tube, precursor to the central nervous system. Blocks of muscle tissue called somites, from which major organs and glands will arise, form along the embryo’s dorsal surface. Blood vessels and the beginnings of the digestive cavity appear by the end of the week. At the close of the first month, all major organs have begun their development. The eyes are visible, the arms and legs begin to bud, and the four-chambered heart beats for the first time. Encarta Encyclopedia © Microsoft Corporation. All Rights Reserved.
	Full Size

In the third week a closed tube appears in which the brain and spinal cord are to develop. Another tube, folding on itself, is developing into the heart, and at about this stage a portion of the minute yolk sac is enclosed in the body of the embryo to form a part of the embryonic alimentary canal. At the beginning of its fourth week the embryo, now about 4 to 5 mm (about 0.16 to 0.2 in) long, has the rudiments of eyes and ears, and each side of the neck shows four gill clefts. A tail is also present.

Early in the second month the buds of the arms and legs appear. The major internal organs begin to take shape, and in about the sixth week bones and muscles begin to form. By the third month the embryo is recognizable as that of a primate, and is now called a fetus. It has a definite face, with the mouth and nostrils distinct, and the external ears are forming. By the end of the eighth week the tail has usually been incorporated in the body, and in the 11th or 12th week the external genitals become evident. The human embryo is especially vulnerable to the damaging effects of X rays, of disease viruses such as measles, and of certain drugs during the fourth to the eighth week of gestation. These agents can result in the death of the embryo or in the birth of a child with deformed limbs or other abnormalities. By the fourth month an embryo has developed obvious human features. For development in the fetal stage, see Fetus. For abnormalities due to anomalous development, see Birth Defects. See also Development; Multiple Birth; Obstetrics.

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HUMAN EMBRYOLOGY

The human ovum, fertilized high in a fallopian tube, is brushed by the hairlike cilia in the tube toward the uterus, where it becomes implanted, that is, attached to and enclosed by decidual tissue of the uterine lining. Studies of primate embryos indicate that, in humans as well as in apes, cell multiplication begins during the journey of the ovum through the tube. The implanted embryo consists of a hollow sphere, the blastocyst, containing a mass of cells, called the embryonic mass, attached by a stalk to one side of the encircling membrane. In a blastocyst less than two weeks old and measuring 1 mm (0.04 in) in diameter, the microscope reveals the amnion (a sac surrounding the embryo), chorion (a membrane that develops around the amnion and lines the uterine wall), yolk sac, and distinct germ layers.

	Developing Embryo's First Month Thirty hours after conception, the fertilized egg undergoes its first cell division. The embryo, as it is now called, continues to divide as it travels down the fallopian tube. It implants in the uterine lining approximately six days after fertilization, a ball of cells with a disk-shaped embryonic mass. In the second week, the placenta begins to form, nourishing an embryo now composed of the three primary types of tissue: endoderm, ectoderm, and mesoderm. The third week sees the formation of the neural tube, precursor to the central nervous system. Blocks of muscle tissue called somites, from which major organs and glands will arise, form along the embryo’s dorsal surface. Blood vessels and the beginnings of the digestive cavity appear by the end of the week. At the close of the first month, all major organs have begun their development. The eyes are visible, the arms and legs begin to bud, and the four-chambered heart beats for the first time. Encarta Encyclopedia © Microsoft Corporation. All Rights Reserved.
	Full Size

In the third week a closed tube appears in which the brain and spinal cord are to develop. Another tube, folding on itself, is developing into the heart, and at about this stage a portion of the minute yolk sac is enclosed in the body of the embryo to form a part of the embryonic alimentary canal. At the beginning of its fourth week the embryo, now about 4 to 5 mm (about 0.16 to 0.2 in) long, has the rudiments of eyes and ears, and each side of the neck shows four gill clefts. A tail is also present.

Early in the second month the buds of the arms and legs appear. The major internal organs begin to take shape, and in about the sixth week bones and muscles begin to form. By the third month the embryo is recognizable as that of a primate, and is now called a fetus. It has a definite face, with the mouth and nostrils distinct, and the external ears are forming. By the end of the eighth week the tail has usually been incorporated in the body, and in the 11th or 12th week the external genitals become evident. The human embryo is especially vulnerable to the damaging effects of X rays, of disease viruses such as measles, and of certain drugs during the fourth to the eighth week of gestation. These agents can result in the death of the embryo or in the birth of a child with deformed limbs or other abnormalities. By the fourth month an embryo has developed obvious human features. For development in the fetal stage, see Fetus. For abnormalities due to anomalous development, see Birth Defects. See also Development; Multiple Birth; Obstetrics.

Read More

HUMAN EMBRYOLOGY

The human ovum, fertilized high in a fallopian tube, is brushed by the hairlike cilia in the tube toward the uterus, where it becomes implanted, that is, attached to and enclosed by decidual tissue of the uterine lining. Studies of primate embryos indicate that, in humans as well as in apes, cell multiplication begins during the journey of the ovum through the tube. The implanted embryo consists of a hollow sphere, the blastocyst, containing a mass of cells, called the embryonic mass, attached by a stalk to one side of the encircling membrane. In a blastocyst less than two weeks old and measuring 1 mm (0.04 in) in diameter, the microscope reveals the amnion (a sac surrounding the embryo), chorion (a membrane that develops around the amnion and lines the uterine wall), yolk sac, and distinct germ layers.

	Developing Embryo's First Month Thirty hours after conception, the fertilized egg undergoes its first cell division. The embryo, as it is now called, continues to divide as it travels down the fallopian tube. It implants in the uterine lining approximately six days after fertilization, a ball of cells with a disk-shaped embryonic mass. In the second week, the placenta begins to form, nourishing an embryo now composed of the three primary types of tissue: endoderm, ectoderm, and mesoderm. The third week sees the formation of the neural tube, precursor to the central nervous system. Blocks of muscle tissue called somites, from which major organs and glands will arise, form along the embryo’s dorsal surface. Blood vessels and the beginnings of the digestive cavity appear by the end of the week. At the close of the first month, all major organs have begun their development. The eyes are visible, the arms and legs begin to bud, and the four-chambered heart beats for the first time. Encarta Encyclopedia © Microsoft Corporation. All Rights Reserved.
	Full Size

In the third week a closed tube appears in which the brain and spinal cord are to develop. Another tube, folding on itself, is developing into the heart, and at about this stage a portion of the minute yolk sac is enclosed in the body of the embryo to form a part of the embryonic alimentary canal. At the beginning of its fourth week the embryo, now about 4 to 5 mm (about 0.16 to 0.2 in) long, has the rudiments of eyes and ears, and each side of the neck shows four gill clefts. A tail is also present.

Early in the second month the buds of the arms and legs appear. The major internal organs begin to take shape, and in about the sixth week bones and muscles begin to form. By the third month the embryo is recognizable as that of a primate, and is now called a fetus. It has a definite face, with the mouth and nostrils distinct, and the external ears are forming. By the end of the eighth week the tail has usually been incorporated in the body, and in the 11th or 12th week the external genitals become evident. The human embryo is especially vulnerable to the damaging effects of X rays, of disease viruses such as measles, and of certain drugs during the fourth to the eighth week of gestation. These agents can result in the death of the embryo or in the birth of a child with deformed limbs or other abnormalities. By the fourth month an embryo has developed obvious human features. For development in the fetal stage, see Fetus. For abnormalities due to anomalous development, see Birth Defects. See also Development; Multiple Birth; Obstetrics.

Read More

HUMAN EMBRYOLOGY

The human ovum, fertilized high in a fallopian tube, is brushed by the hairlike cilia in the tube toward the uterus, where it becomes implanted, that is, attached to and enclosed by decidual tissue of the uterine lining. Studies of primate embryos indicate that, in humans as well as in apes, cell multiplication begins during the journey of the ovum through the tube. The implanted embryo consists of a hollow sphere, the blastocyst, containing a mass of cells, called the embryonic mass, attached by a stalk to one side of the encircling membrane. In a blastocyst less than two weeks old and measuring 1 mm (0.04 in) in diameter, the microscope reveals the amnion (a sac surrounding the embryo), chorion (a membrane that develops around the amnion and lines the uterine wall), yolk sac, and distinct germ layers.

	Developing Embryo's First Month

	Developing Embryo's First Month Thirty hours after conception, the fertilized egg undergoes its first cell division. The embryo, as it is now called, continues to divide as it travels down the fallopian tube. It implants in the uterine lining approximately six days after fertilization, a ball of cells with a disk-shaped embryonic mass. In the second week, the placenta begins to form, nourishing an embryo now composed of the three primary types of tissue: endoderm, ectoderm, and mesoderm. The third week sees the formation of the neural tube, precursor to the central nervous system. Blocks of muscle tissue called somites, from which major organs and glands will arise, form along the embryo’s dorsal surface. Blood vessels and the beginnings of the digestive cavity appear by the end of the week. At the close of the first month, all major organs have begun their development. The eyes are visible, the arms and legs begin to bud, and the four-chambered heart beats for the first time. Encarta Encyclopedia © Microsoft Corporation. All Rights Reserved.
	Full Size

In the third week a closed tube appears in which the brain and spinal cord are to develop. Another tube, folding on itself, is developing into the heart, and at about this stage a portion of the minute yolk sac is enclosed in the body of the embryo to form a part of the embryonic alimentary canal. At the beginning of its fourth week the embryo, now about 4 to 5 mm (about 0.16 to 0.2 in) long, has the rudiments of eyes and ears, and each side of the neck shows four gill clefts. A tail is also present.

Early in the second month the buds of the arms and legs appear. The major internal organs begin to take shape, and in about the sixth week bones and muscles begin to form. By the third month the embryo is recognizable as that of a primate, and is now called a fetus. It has a definite face, with the mouth and nostrils distinct, and the external ears are forming. By the end of the eighth week the tail has usually been incorporated in the body, and in the 11th or 12th week the external genitals become evident. The human embryo is especially vulnerable to the damaging effects of X rays, of disease viruses such as measles, and of certain drugs during the fourth to the eighth week of gestation. These agents can result in the death of the embryo or in the birth of a child with deformed limbs or other abnormalities. By the fourth month an embryo has developed obvious human features. For development in the fetal stage, see Fetus. For abnormalities due to anomalous development, see Birth Defects. See also Development; Multiple Birth; Obstetrics.

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AGSRICUS

                                                             Division – Eumycota

                                                                     Class – Basidomycetes 

                                                                 Order –Agaricales

                                                                           Family – Agericaceae  

                                                                       Genus – Agericus

Occrance : It growth on damp rotten of wood , dead and decaying organic matters. Soil rich in hums in humus and manure piles. It includes many species, the majorities of them being edible. Agericus compestris is the best known species and quite commonly known as field musroom , it is commonly seen growing on grass field and other places rich in humus soil, during rainy season .Being it is cultivated

Structure : The vagetative body is the mycelium when is found growing below ground. The areal frutication basidiocarp is produced at time of reproduction and is called mushroom which is edible porton. The mycelium, when young is haploid and consist of much branched , loosely tangled felt of septal hypage which ramify the substrum just benth the surface .the cell of these hyphae are unicelaute

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Alternaria

                                           Division – Mycota

                                                                      Class – deuteromycetes

                                                                Order –moniliales

                                                                           Family – Dematiaceae

                                                                       Genus – Alternaria

Occorancer : species of alternaria are Saparophytic as well as week parasites Fungus . They are cosmopolitant in distribution in nature. They are found abundantly in house dust and cause of chiffuncai HAY FEVER . alternia solani cause dark leaf spote in brassica species . a triticina cause leaf blight of wheet .

Mycelium is septale . branched and spread to intercellular spaces of the host tissue without historia . it is light brown colour becomes black coloured.

Alternaria , reproduce only by Asexual method by meansof conidia , which are born at the tip of conidiophore. They are short and dark colour . emerge through the stomata or from the death or damage parts of host  leaves. Conidia are borne on the coniodiophore from a bud which is formed on that cell. Conidia are born singly but sometiimes they are formed in chain of two or three . the conidia are large dark colore mostly obclavate , terminating in long , septal , beak

Like structure. The body of conidium is divides into small compartments the conidia vary in size but they are large bottle shapr multicellular with both trsnsverse and longitudnal septaoccring typically. The conidia when mature get deached and are displaced by wind. Under favourable condition conidia germinated readly and five rotten germ tube arise from single conidium 

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Gene Therapy

Gene Therapy, experimental medical treatment that manipulates a gene or genes within cells in order to produce proteins that change the function of those cells. Gene therapy originated in efforts to treat and cure some of the more than 9,000 known genetic disorders, most of which lack an effective therapy. In the United States 1 infant in every 28 is born with a disorder caused by a defect in 1 or more of the estimated 31,000 genes found in the human body. Thousands of children and adolescents die from these diseases each year, and tens of thousands suffer lifelong disability. Although gene therapy is not an approved medical therapy to treat disease, over 400 clinical trials, experiments testing the safety and efficacy of this method on humans, have been conducted in the United States. Scientists expect that within the first decades of the 21st century, gene therapy will offer unprecedented opportunities to treat, cure, and ultimately prevent a vast range of diseases.

The original goal of gene therapy was to substitute a healthy gene for a defective one, or to repair a faulty gene, thereby eliminating symptoms of disease. But researchers have moved beyond inherited genetic disorders to treat other kinds of diseases. Today, nearly 75 percent of all clinical trials involving gene therapy are aimed at treatments for cancer and acquired immunodeficiency syndrome (AIDS). Cancer begins in genes and may be caused by an inherited defect or a mutation (permanent alteration to a gene) that causes a cell to malfunction. AIDS is caused by a virus that disrupts the genetic material of immune cells. Other new gene therapy projects are targeted at conditions such as heart disease, diabetes mellitus, arthritis, and Alzheimer's disease, all of which involve genetic susceptibility to illness. Gene therapists hope to reduce or eliminate this susceptibility. Eventually, gene therapy might help older people to regain strength in withered muscles and density in thinned bones, and to increase pumping power in their aging hearts. Some researchers predict that in the distant future the technology could be used to eliminate genetic defects from families or even to produce “designer babies” with more muscle strength, higher intelligence, sweeter dispositions, or whatever traits parents desire.

Although gene therapy offers seemingly limitless possibilities, researchers have been thwarted by many technical problems. There has only been one successful clinical trial using gene therapy—in April 2000 French researchers reported the successful use of gene therapy to treat two female infants with severe combined immunodeficiency disease (SCID), a deadly inherited disease that impairs the immune system. But even this success was marred when each child later developed a rare leukemia-like illness, thought to be a result of gene therapy. Most clinical trials of gene therapy have not resulted in enough improvement in the patient’s underlying condition to consider it an unqualified success and to justify treating large numbers of people. The extraordinary potential of gene therapy has also raised alarms among critics who warn that the technology could go too far. They note, for example, that gene therapy could offer wealthy families opportunities for genetic enhancement unavailable to the poor. More troubling still for some critics is gene therapy's potential to narrow the human gene pool, producing unknown, and possibly harmful, consequences.

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