organogenesistossif-131119105135-phpapp02.pdf

organogenesistossif-131119105135-phpapp02.pdf

• 1.
  Organogenesis Critical period ofOrganogenesis By: Gajaan S Tossif G 512
• 2.
  Organogenesis Organogenesis is theprocess by which the ectoderm, endoderm, and mesoderm develop into the internal organs of the organism. Cells of each germ layer proliferate, migrate, reaggregate and differentiate into various tissues that form the organs (organogenesis)
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  How does itoccur? The germ layers in organogenesis differ by three processes: • folds, • splits, and • Condensation Cells of each germ layer proliferate, migrate, reaggregate and differentiate into various tissues that form the organs (organogenesis)
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  When does itoccur? Internal organs initiate development in humans within the 3rd to 8th weeks in utero.
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  Embryonic stage • Week3: Beginning development of the brain, heart, blood cells, circulatory system, spinal cord, and digestive system. • Week 4: Beginning development of bones, facial structures, and limbs (presence of arm and leg buds); continuing development of the heart (which begins to beat), brain, and nervous tissue. • Week 5: Beginning development of eyes, nose, kidneys, lungs; continuing development of the heart (formation of valves), brain, nervous tissue, and digestive tract. • Week 6: Beginning development of hands, feet, and digits; continuing development of brain, heart, and circulation system. • Week 7: Beginning development of hair follicles, nipples, eyelids, and sex organs (testes or ovaries); first formation of urine in the kidneys and first evidence of brain waves. • Week 8: Facial features more distinct, internal organs well developed, the brain can signal for muscles to move, heart development ends, external sex organs begin to form. By the end of the embryonic stage, all essential external and internal structures have been formed. The embryo is now referred to as a fetus.
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  CRITICAL PERIODS OFDEVELOPMENT It is a specific time during which the environment has its greatest impact on an individual's development.
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  if you drink,I will also drink
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  Why it iscritical period? Because it will disturb the processes of developments: • Control of cell division, • Apoptosis, • Gene expression, and • Cellular metabolism
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  During pre-embronic stage •The effects of maternal drug use on the development of the fetus are dependent upon the stage of embryonic and fetal development, as well as the dosage of the substance. After fertilization occurs, the embryo is highly resistant to birth defects, but the results of a high dose teratogen could result in death. Intake of teratogens during this preembryonic stage could also result in normal development if the teratogenic substance is stopped before the embryonic stage of development.
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  During embryonic stage •During the embryonic stage of development (weeks 3-8), the effects of teratogens are increasingly detrimental. Organs begin forming during the embryonic stage, and harmful teratogens can result in miscarriage, and structural abnormalities. • Once the embryonic stage is complete, the fetal period begins at week 9 and continues until full term at week 38. Teratogens taken during this period can result in improper organ functioning, delayed growth, but seldom result in birth defects .