It Takes Teamwork

Sperm Anatomy Acrosome enzymes: hyaluronidase, acrosin, neuraminidase

Fertilization and Implantation Eggs are viable for 72 hours Sperm is viable for 48 hours Implantation occurs about 5-6 days after conception

Development Week 1 Blastocyst Inner Cell Mass (Embryonic Stem Cells)

Developmental Week 2 Embryonic Germ Cell Layers: Endoderm Mesoderm Ectoderm

Neural Development (Weeks 3-4) Neural Plate Neural Groove Neural Fold Neural Crest Neural Tube

Neural Tube Defects Anencephaly: Failed closure of the Anterior Neuropore Spina Bifida: Failed closure of the Posterior Neuropore

Steps in Neural Development Mitosis Migration Differentiation Dendritic Sprouting and Bulb Growth Synaptogenesis Cell Death Dendritic Pruning Myelination

Mitosis

Migration Growth Cones form and use: Radial Glia Contact Inhibition Contact Adhesion Fasciculation Guide Posts Chemotropism

Growth Cones Growth Cone

Radial Glia Act like scaffolding to assist movement of neurons during development

Contact Inhibition/Adhesion The growth cones of migrating cells can be attracted to other cell surfaces by contact adhesion molecules on those cells. Likewise, growth cones of migrating cells can be repelled from other cell surfaces by contact inhibition molecules on those cells.

Fasciculation Adhesion molecules allow the bonding of same type axons to form a nerve bundle.

Guide Posts Intermediate targets that help guide or direct the growth cone of the migrating cell in the proper direction

Chemotropism Target Cell or Tissue Target tissues or cells can release chemicals that will attract the specific growth cones of migrating cells.

Differentiation

Dendritic Sprouting

Synaptogenesis

Cell Death and Dendritic Pruning

Myelination Major growth occurs from birthto 2 years of age Cephalocaudal Development: from head to toe (tail) Proximodistal Development: from midline to the periphery Readiness Principle: Until children reach a state of readiness, they will be unable to perform a task, even with training and practice.