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GASTRULATION, NOTOCHORD AND NEURULATION COURSETITLE: General Embryology LECTURER: Dr Sabiu B. SOJA UNIT: Epigenetics/ Developmental Anatomy DATE : 27TH October 2024
GASTRULATION 2 Is the process that establishes 3 germ cell layers: Trilaminar germ disc at the 3rd week of embryonic development Begins with formation of primitive streak on surface of epiblast Which has an orientation with the cephalic end marked by the primitive node and pit
GASTRULATION (CONTD) 3 Epiblast cells migrate to the primitive streak, detach and slip underneath, Displacing the hypoblast and becoming the endoderm Subsequent layer of cells develops between this endoderm and the epiblast- these form the mesoderm The remaining epiblast now is referred to as the ectoderm.
GASTRULATION (CONTD) 4
GASTRULATION (CONTD) 5 Following gastrulation, The bilaminar disc of blastula is transformed into Trilamina disc, Which consists of three primary germ layers; the ectoderm, mesoderm and endodermal layers
NOTOCHORDAL FORMATION 6 Invagination cells that migrate cephalad form the prechodal plate, that is significant in induction of the forebrain It is situated close to the buccopharnyngeal membrane Also , the migrating cells form the notochord That extends from the prechordal plate cranially to the primitive pit caudally.
NOTOCHORDAL FORMATION 7 The Cloacal membrane is formed at the caudal end of the embryonic disk- formed
NEURULATION 8 Is the formation of the neural tube Notochord induces the overlying ectoderm to thicken and form the neural plate At the end of 3rd week, neural folds and neural groove are established.
NEURULATION (CONTD) 9
NEURULATION (CONTD) 10 Neural folds fuse in the midline, from the cervical region and extending cranially and caudally.
NEURULATION (CONTD) 11
NEURULATION (CONTD) 12 Neural tube is formed and invade into the embryo body
NEURULATION 13 The broader cephalic portion of the neural tube transforms into primary brain vesicles The narrower part develops into the spinal cord
NEURULATION (CONTD) 14 Primary and Secondary Vesicle Stages of Development The embryonic brain develops complexity through enlargements of the neural tube called vesicles; (a) The primary vesicle stage has three regions, and (b) the secondary vesicle stage has five regions. Credit: OpenStax.
SOMITES 15 Mesodermal cells on each side of the neural tube begin to form a row of regular, compact structures called somites
SOMITES (CONTD) 16 A. Dorsal view of a human embryo at about day 22 B. Dorsal view of a human embryo at about day 23. The nervous system is in connection with the amniotic cavity through the cranial and caudal neuropores Closure of the cranial neuropore happens at about day 25(18-20-somite stage) Posterior neuropore closes at approximately day 27 (25- somite stage)
NEURAL CREST CELLS 17 Along the line of fusion of the neural folds, some of the cells break free and become migratory within the mesodermal layer. These are the neural crest cells, and are shown here as tan-coloured clusters of cells resembling 'teardrops' alongside the neural tube Neural crest cell
NEURAL CREST CELLS (CONTD) 18
19
CLINICAL CONSIDERATION 20 NTDs occur due to defect in the midline fusion of neural tube Resulting in cranial or spinal dysraphism, and may involve nerve roots, spinal cord, or bony vertebrae. They can be open or closed types NEURALTUBE DEFECTS(NTDs)
CLINICAL CONSIDERATION 21 The causes are mostly multifactorial, including both genetic and environmental causes. Mutations in several genes, especially genes involved in folic acid metabolism, have been found
CLINICAL CONSIDERATION 22 Failure of cranial neuropore results to anencephalic child or meningocele. Failure of posterior neuropore results in rachischisis or meningomyelocele.
CLINICAL CONSIDERATION 23
CLINICAL CONSIDERATION 24
GASTRULATION, NOTOCHORD AND NEURULATION.pptx
CLINICAL CONSIDERATION 26
CLINICAL CONSIDERATION 27
CLINICAL CONSIDERATION 28
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GASTRULATION, NOTOCHORD AND NEURULATION.pptx

  • 1. GASTRULATION, NOTOCHORD AND NEURULATION COURSETITLE: General Embryology LECTURER: Dr Sabiu B. SOJA UNIT: Epigenetics/ Developmental Anatomy DATE : 27TH October 2024
  • 2. GASTRULATION 2 Is the process that establishes 3 germ cell layers: Trilaminar germ disc at the 3rd week of embryonic development Begins with formation of primitive streak on surface of epiblast Which has an orientation with the cephalic end marked by the primitive node and pit
  • 3. GASTRULATION (CONTD) 3 Epiblast cells migrate to the primitive streak, detach and slip underneath, Displacing the hypoblast and becoming the endoderm Subsequent layer of cells develops between this endoderm and the epiblast- these form the mesoderm The remaining epiblast now is referred to as the ectoderm.
  • 5. GASTRULATION (CONTD) 5 Following gastrulation, The bilaminar disc of blastula is transformed into Trilamina disc, Which consists of three primary germ layers; the ectoderm, mesoderm and endodermal layers
  • 6. NOTOCHORDAL FORMATION 6 Invagination cells that migrate cephalad form the prechodal plate, that is significant in induction of the forebrain It is situated close to the buccopharnyngeal membrane Also , the migrating cells form the notochord That extends from the prechordal plate cranially to the primitive pit caudally.
  • 7. NOTOCHORDAL FORMATION 7 The Cloacal membrane is formed at the caudal end of the embryonic disk- formed
  • 8. NEURULATION 8 Is the formation of the neural tube Notochord induces the overlying ectoderm to thicken and form the neural plate At the end of 3rd week, neural folds and neural groove are established.
  • 10. NEURULATION (CONTD) 10 Neural folds fuse in the midline, from the cervical region and extending cranially and caudally.
  • 12. NEURULATION (CONTD) 12 Neural tube is formed and invade into the embryo body
  • 13. NEURULATION 13 The broader cephalic portion of the neural tube transforms into primary brain vesicles The narrower part develops into the spinal cord
  • 14. NEURULATION (CONTD) 14 Primary and Secondary Vesicle Stages of Development The embryonic brain develops complexity through enlargements of the neural tube called vesicles; (a) The primary vesicle stage has three regions, and (b) the secondary vesicle stage has five regions. Credit: OpenStax.
  • 15. SOMITES 15 Mesodermal cells on each side of the neural tube begin to form a row of regular, compact structures called somites
  • 16. SOMITES (CONTD) 16 A. Dorsal view of a human embryo at about day 22 B. Dorsal view of a human embryo at about day 23. The nervous system is in connection with the amniotic cavity through the cranial and caudal neuropores Closure of the cranial neuropore happens at about day 25(18-20-somite stage) Posterior neuropore closes at approximately day 27 (25- somite stage)
  • 17. NEURAL CREST CELLS 17 Along the line of fusion of the neural folds, some of the cells break free and become migratory within the mesodermal layer. These are the neural crest cells, and are shown here as tan-coloured clusters of cells resembling 'teardrops' alongside the neural tube Neural crest cell
  • 18. NEURAL CREST CELLS (CONTD) 18
  • 19. 19
  • 20. CLINICAL CONSIDERATION 20 NTDs occur due to defect in the midline fusion of neural tube Resulting in cranial or spinal dysraphism, and may involve nerve roots, spinal cord, or bony vertebrae. They can be open or closed types NEURALTUBE DEFECTS(NTDs)
  • 21. CLINICAL CONSIDERATION 21 The causes are mostly multifactorial, including both genetic and environmental causes. Mutations in several genes, especially genes involved in folic acid metabolism, have been found
  • 22. CLINICAL CONSIDERATION 22 Failure of cranial neuropore results to anencephalic child or meningocele. Failure of posterior neuropore results in rachischisis or meningomyelocele.