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Introduction to Embryology

Introduction to Embryology. Dr. Khaldoun Darwich Ph.D. in Oral and Maxillofacial Surgery. Syllabus. Why do we study Embryology?. “the one who sees things from the beginning will have the finest view of them” Aristotle , 384 - 322 B.C.

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Introduction to Embryology

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  1. Introduction to Embryology Dr. KhaldounDarwich Ph.D. in Oral and Maxillofacial Surgery

  2. Syllabus

  3. Why do we study Embryology?

  4. “the one who sees things from the beginning will have the finest view of them” Aristotle, 384 - 322 B.C.

  5. It is important for dental professionals to understand the major events of prenatal development to understand better the development of the structures of the face, neck,and oral tissue and the underlying relationships among these structures

  6. What is EMBRYOLOGY?

  7. Embryology • Definition: • Is the study of prenatal development

  8. Prenatal period: In Humans, prenatal development begins at the start of pregnancy and continues until the birth of the child. 38 weeks from conception to birth

  9. Terminology Different to that used in gross anatomy

  10. Prenatal development : Consists of three distinct periods

  11. Periods of Prenatal development : • Preimplantation period • Embryonic period • Fetal period

  12. Preimplantation Period

  13. Developmental Disturbances during prenatal development These developmental problems can include congenital malformations or birth defects, which are developmental problems evident at birth.

  14. Developmental Disturbances during prenatal development Most of these occur during both the preimplantation period and the embryonic period and thus the first trimester of the pregnancy

  15. Developmental Disturbances during prenatal development Statistics show that such malformations occur with an incidence of 1 in 700 live births. This does not include anatomical variants which are common, such as variation in the lesser details of a bone’s shape.

  16. Developmental Disturbances during prenatal development Malformations can be due to genetic factors such as chromosome abnormalities or enviromental factors. These enviromental factors can include infections, drugs, and radiation and are called teratogens.

  17. Teratogens • Enviromental influences or agents that can damage the developing organism

  18. Teratogens • Women of reproductive age should avoid teratogens at the time of their first missed menstrual period and thereafter to protect the developing human

  19. Influence of Teratogens • Larger doses, over time, more negative • Genetics can help or hinder teratogens • Several negative factors increase impact • Sensitive periods especially important • Embryonic period most susceptible • Physical and psychological effects

  20. Drugs • Thalidomide – sedative - 1960’s • Aspirin - low birth weight, infant deathPoor motor develop., lower IQ • Heavy caffeine use - miscarriagePremature births, irritability

  21. Illegal Drugs • Cocaine, heroin, methadone • Prematurity, low birth weight • Physical defects, breathing problems, • Drug addiction & death • Cocaine - lasting difficulties • Genital, urinary tract, kidney, heart deformities • Brain seizures

  22. Tobacco use • Low birth weight and premature births • Impaired breathing • Miscarriage & infant death • Placenta doesn’t work correctly • Greater concentration of carbon monoxide • Passive smoking also injurious

  23. Alcohol • Fetal alcohol syndrome (FAS) • Large amounts of alcohol, whole pregnancy • Mental retardation • Slow physical growth • Facial abnormalities • Alcohol interferes with cell duplication • Especially neural cells • Draws oxygen away from organism

  24. Fetal Alcohol Syndrome

  25. Hormones • Diethylstilbestrol (DES), 1945-70 • Vaginal cancer • Malformation of the uterus • Miscarriage, low birth weight

  26. Radiation • Hiroshima & Nagasaki • Miscarriage, slow physical growth • Underdeveloped brains • Malformation of skeleton & eyes • X-Rays - avoid during pregnancy

  27. Environmental Pollutants (Chemicals) • Mercury • Mental retardation, speech problems • Difficulty chewing & swallowing • Uncoordinated movements • Polychlorinated Biphenyl (PCB) • Lower birth weight, smaller heads • Poor memory, lower verbal IQ

  28. Infections • Viruses - Most not harmful • Rubella • Heart defects, cataracts, deafness • Genital, urinary & intestinal problems • HIV & AIDS • 20-30% Mothers pass to infants • Most survive 5 to 8 months

  29. Malformations In the face, neck, and oral cavity range from serious clefts in the face or palate region to small deficiencies of the soft palate or cysts underneath an otherwise intact oral mucosa.

  30. It is important for dental professionals to remember that : Any orofacial congenital malformations found when examining a patient are understandable and traceable to a specific time in the embryological development of the individual.

  31. Preimplantation period of prenatal development: It takes place during the first week. At the beginning of the first week a woman’s ovum is penetrated by and united with a man’s sperm during fertilization

  32. Week 1 FERTILIZATION

  33. Week 1 FERTILIZATION Passage of sperm through corona radiata surrounding the zona pellucida Hyaluronidase from sperm acrosome Changes the makeup of zona pellucida

  34. Week 1 FERTILIZATION • Zona reaction occurs – lysosomal enzymes released by cortical granules near plasma membrane of oocyte Esterases, acrosin, and neuramidase released from acrosome • Completion of second meiotic divison occurs with formation of male and female pronucleus

  35. Preimplantation period of prenatal development: This union of the ovum and sperm subsequently forms a fertilized egg, or zygote during fertilization the final stage of meiosis occur in the ovum .

  36. At conception in fallopian tube, maternal and paternal genetic material join to form a new human life (zygote)

  37. Meiosis The result of this process is the joining of the ovum’schromosomes with those of the sperm. This joining of chromosomes from both biological parents forms a new individual with shuffled chromosomes

  38. Meiosis this process enables the ovum and sperm to reduce by one half the normal number of chromosomes ( to a haploid number of 23 ) Thus the zygote has received half its chromosomes from the female and half from the male with the resultant genetic material a reflection of both biological parents

  39. Week 1 post conception Zygote Morula Blastocyst

  40. Mitosis After fertilization the zygote then undergoes Mitosis or individual cell division or cleavage

  41. Morula After initial cleavage the solid ball of cells is known as a morula

  42. Blastula Because of the ongoing process of mitosis and secretion of fluid by the cells within the morula the zygote becomes a vesicle known as a blastocyst (Blastula) The rest of the first week is characterized by further mitotic cleavage , in which the blastocyst splits into smaller and more numerous cells as it undergoes successive cell divisions by mitosis

  43. Mitosis and Meiosis What is Mitosis? a type of cell division that results in daughter cells each with the same number and kind of chromosomes as the parent cell. This type of cell division allows multicellular organisms to grow and repair damaged tissue

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