1 embryology

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  • In humans, the notochord forms in week 3, is eventually lost from vertebral regions and contributes to the nucleus pulposus of the intervertebral disc during the formation of the vertebral column.
  • The central region of the ectoderm forms a columnar epithelium described as the neural plate. This epithelium will fold dorsally to form the neural groove , which then fuses to form an initially open at either end hollow neural tube . The neural tube forms the central nervous system (brain and spinal cord).
  • 1 embryology

    1. 1. DHS 2 General Embryology Lecture 1 Original Lecture: Prof. Grant Townsend, University of Adelaide Dr. Sausan Al Kawas University of Sharjah
    2. 2. Objectives <ul><li>To provide a general description of human embryological processes as follows: </li></ul><ul><li>Germ cell formation & fertilization </li></ul><ul><li>Prenatal development </li></ul><ul><li>Induction, competence, and differentiation </li></ul><ul><li>Formation of three-layerd embryo </li></ul><ul><li>Formation of neural crest </li></ul><ul><li>Formation of human tissues </li></ul><ul><li>Folding of the embryo </li></ul>Copyright © 2006/07 The University of Sharjah slide
    3. 3. Embryology <ul><li>Embryology is literally “the study of the embryo” </li></ul><ul><li>More generally it refers to “the study of prenatal development” </li></ul><ul><ul><li>Embryo = 2-8 weeks </li></ul></ul><ul><ul><li>Foetus = 9 weeks to birth </li></ul></ul>Copyright © 2006/07 The University of Sharjah slide UNSW Embryology 2007
    4. 4. Embryology <ul><li>Ontogeny : stages of development of an individual </li></ul><ul><li>Teratology : study of abnormal development (congenital malformations) </li></ul>Copyright © 2006/07 The University of Sharjah slide UNSW Embryology 2007
    5. 5. Mitosis and Meiosis Copyright © 2006/07 The University of Sharjah slide
    6. 6. Gametogenesis <ul><li>Gametogenesis is a process of formation and development of male(sperm) and female (ovum)gametes. </li></ul><ul><li>During this process a reduction of the the number of chromosomes takes place from diploid number (46) of primary germ cells to the haploid number (23) in the mature germ cell. </li></ul>Copyright © 2006/07 The University of Sharjah slide
    7. 7. Gametogenesis <ul><li>It also involves the chromosomal and the cytoplasmic changes. </li></ul><ul><li>These alteration of the shape of the primary germ cells allow them to become ready for fertilization. </li></ul>Copyright © 2006/07 The University of Sharjah slide
    8. 8. Gametogenesis <ul><li>The large rounded primary male germ cells, lose most of their cytoplasm and develop head, tail and neck to assist in the movement of the sperms. </li></ul><ul><li>The rounded female germ cells become larger as a result of increase in the a mount of their cytoplasm and called ovum. </li></ul>Copyright © 2006/07 The University of Sharjah slide Mature sperm Mature oocyte
    9. 9. Fertilization <ul><li>The fertilization occur when sperm contacts an ovum to form a zygote in the uterine tube. </li></ul><ul><li>The zygote, which contains 46 chromosomes, rapidly divide by mitosis to form mass of cells as 2,4, 8, 16, 32…. </li></ul><ul><li>This mass of cells continue dividing in order to give the different tissues then organs of the human body. </li></ul>Copyright © 2006/07 The University of Sharjah slide Ref: Dental Embryology, Histology, and Anatomy
    10. 10. General Embryology Copyright © 2006/07 The University of Sharjah slide These images reproduced from Dr. Di Marzo Mature Human Egg Fertilized Human Zygote 4 Cell Human Embryo UNSW Embryology 2010
    11. 11. General Embryology <ul><li>Fertilization </li></ul><ul><ul><li>Zygote </li></ul></ul><ul><ul><li>Genotype, environment, phenotype </li></ul></ul><ul><li>Induction, competence, differentiation </li></ul><ul><li>Formation of the three layered embryo </li></ul><ul><ul><li>Morula, blastocyst, bilaminar then trilaminar germ disc </li></ul></ul><ul><ul><li>Ectoderm, endoderm, mesoderm </li></ul></ul><ul><li>Formation of neural crest cells </li></ul><ul><li>Folding of the embryo </li></ul>Copyright © 2006/07 The University of Sharjah slide
    12. 12. Copyright © 2006/07 The University of Sharjah slide
    13. 13. Copyright © 2006/07 The University of Sharjah slide . General Embryology Ref: Dental Embryology, Histology, and Anatomy Uterine tube Uterus Ovary
    14. 14. Copyright © 2006/07 The University of Sharjah slide General Embryology Ref: Dental Embryology, Histology, and Anatomy Division of the zygote Zygote. Formation of the morula Morula Blastula
    15. 15. Structure of the blastocyt (blastula): Copyright © 2006/07 The University of Sharjah slide
    16. 16. Copyright © 2006/07 The University of Sharjah slide Implantation of the blastocyte: Uterine wall Endometrium Digested endometrium Blastocyte
    17. 17. Copyright © 2006/07 The University of Sharjah slide Formation of embryonic layers: second week Ref: Dental Embryology, Histology, and Anatomy Bilaminar embryonic disc Secondary Yolk sac Endometrium Hypoblast amniotic cavity Epiblast
    18. 18. Copyright © 2006/07 The University of Sharjah slide Formation of the tri-laminar disc: Third week Formation of primitive streak at the midline causing the disc to have right and left half, each half will be as mirror to the other Primitive streak Bilaminar disc Epiblast layer Hypoblast layer
    19. 19. Copyright © 2006/07 The University of Sharjah slide Formation of primitive streak Formation of the tri-laminar disc: UNSW Embryology 2007
    20. 20. Copyright © 2006/07 The University of Sharjah slide Formation of the mesodermal layer: Movement of some cells of epiblast toward hypoblast at the primitive streak forms a third embryonic layer called mesoderm. Ectoderm layer Endoderm layer Mesoderm layer
    21. 21. Formation of Neural Crest Copyright © 2006/07 The University of Sharjah slide The nervous system develops as a thickening within ectoderm giving the neural plate.
    22. 22. Formation of Neural Crest <ul><li>Neural plate : w ill fold to form neural groove </li></ul><ul><li>Neural groove : fuses to form neural tube </li></ul><ul><li>Neural tube : Gives rise to brain and spinal cord </li></ul>Copyright © 2006/07 The University of Sharjah slide
    23. 23. Formation of Neural Crest Copyright © 2006/07 The University of Sharjah slide UNSW Embryology 2007
    24. 24. Copyright © 2006/07 The University of Sharjah slide Ref: Human Anatomy & Physiology/ Marieb
    25. 25. Formation of Neural Crest <ul><li>Neural crest cells migrate throughout the body and give rise to: </li></ul><ul><ul><li>Cranial and sensory ganglia and nerves </li></ul></ul><ul><ul><li>Sympathetic neurones </li></ul></ul><ul><ul><li>Schwann cells </li></ul></ul><ul><ul><li>Pigment cells </li></ul></ul><ul><ul><li>Meninges </li></ul></ul><ul><ul><li>Cartilage of branchial arches </li></ul></ul><ul><ul><li>Most of the connective tissue of the face “ectomesenchyme” </li></ul></ul>Copyright © 2006/07 The University of Sharjah slide Ref: Avery (2003) Chapter 1992
    26. 26. Formation of Neural Crest <ul><li>Neural crest is essential in development of the face, neck and oral tissues. </li></ul><ul><li>All tissues of a tooth and its supporting structures, except enamel, are derived from neural crest cells </li></ul>Copyright © 2006/07 The University of Sharjah slide Ref: Avery (2003) Chapter 1992
    27. 27. Copyright © 2006/07 The University of Sharjah slide The embryonic layers are distinct from each other and give rise to specific tissues such as: Nervous system. Sensory epi.of eye , ear & nose. Epidermis, hair and nails. Mammary & cutaneous glands. Epi.of sinuses,oral & nasal cavities . Intra-oral glands. Tooth enamel. Formation of the tissues: Ectoderm
    28. 28. Formation of the tissues: Copyright © 2006/07 The University of Sharjah slide Muscle tissue C.T Bone . Cartilage. Pulp. Dentin . Cementum. PL. Alveolar Bone . Mesoderm Ecto-mesoderm
    29. 29. Formation of the tissues: Copyright © 2006/07 The University of Sharjah slide GI tract epithelium & associated glands. Ref: Dental Embryology, Histology, and Anatomy Endoderm ECTODERM ENDODERM MESODERM
    30. 30. Folding of the embryo <ul><li>Folding in two planes: </li></ul><ul><li>Along longitudinal axis to form the stomatodeum (primitive oral cavity) </li></ul>Copyright © 2006/07 The University of Sharjah slide Ref: Ten Cate (2003) Chapter 2
    31. 31. Folding of the embryo Copyright © 2006/07 The University of Sharjah slide Ref: Ten Cate (2003) Chapter 2 <ul><li>Along lateral axis to form the foregut. </li></ul>Completion of the embryonic period (2-8 week)
    32. 32. Copyright © 2006/07 The University of Sharjah slide Ten Cate (2003) Chapter 2
    33. 33. Copyright © 2006/07 The University of Sharjah slide Thank you

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