Embryology

Catchup

Week 1

Week 3

Week 2

  • Amniotic cavity + Bilaminar embryonic disc
  • Lacunae appear in syncytiotrophoblast + Primary umbilical vesicle
  • Cytotrophoblast + Amnion + primary umbilical vesicle + closing plug
  • Extraembryonic mesoderm + coelom
  • Primary villi
  • Connecting stalk + Amnion + embryonic disc + prechordal plate
  • First missed menstrual period + Primitve streak
  • Stage 7: Migration of mesenchymal cells
  • Trilaminar embryo + Amnion + primitive streak + migration of cells from primitive streak
  • Stage 8: Neiral plate + primitive streak
  • Neural plate + neural groove + Somite + primitive node + primitive streak
  • Stage 9: Brain, Neural groove + Somite + Thyroid gland development
  • Neural groove, first pairs of somites + primitive streak + connecting stalk

Ectoderm

Neuroectoderm

Neural tube

Neural crest

  • Cranial and sensory ganglia and nerves
  • Medulla of suprarenal gland
  • Pigment cells
  • Pharyngeal arch cartilages
  • Head mesenchyme and connective tissue
  • Bulbar and conal ridges in heart
  • CNS
  • Retina
  • Pineal body
  • Posterior part of pituitary gland
  • 1,Fertilisation (zona pellucida)
  • 2, Zygote divides
  • Morula
  • 3,Early blastocyst
  • Late blastocyst (trophoblast)
  • 4, Implanatation: Inner cell mass
  • 5,

Neuralation
Formation of neural tube

Transformation of general ectoderm into thickened neural plate

Shaping of plate so it becomes narrower and longer

Lateral folding of neural plate into neural folds

Fusion of the two most lateral apical surface of neural fold into a neural tube

Desc terms

Inferior

Anterior

Superior

Posterior

Cranial, cephalic

Caudal

Ventral

Dorsal

Neu

Dev of neural plate and neural folds
Stage 7 (18-21)

  • Neural plate is thickening of embryonic ectoderm
  • As notochord (deri mesoderm) elongates, neural plate broadens + extends to oropharyngeal membrane in cranial part of embryo
  • Day 18: Neural plate invaginates along its central axis to form neural groove
  • End third week: Lateral edges neural plate elevated = neural folds

Dev of neural tube

  • Masses of cells detach themselves from lateral side of neural plate and form Neural Crest
  • End of third week: neural folds begun move together and fuse: neural plate to Neural Tube
  • Neural tube separates from surface ectoderm, surface ectoderm fuse + differentiate - epidermis of skin
  • Neuralation completed 4th week

Closure of Neural tube

  • Until fusion is complete, cephalic and caudal ends of neural tube communicate wtih amniotic cavity by: cranial and caudal neuropores

Derivatives

  • CNS
  • Peripheral nervous system
  • Sensory epithelium of ear, nose and eye
  • Epidermis including both hair and nails
  • Subcutaneous glands, mammary glands, pituitary gland, enamel of teeth