Ectoderm

The three regions of the ectoderm

-neural plate

-surface ectoderm

-neural crest

The neural plate forms

the central nervous system

the neural crest forms

-the peripheral nervous system

-cartilages

-bones of head

melanocytes

Surface ectoderm forms

skin, hair, nails, glands

-lens

-cornea

Division of the ectoderm

-surface ectoderm

-neuroectoderm

What specifies the ectoderm into neuroectoderm and epidermal ectoderm?

BMP and its antagonist

Three divisions of anterior axis of neural tube

-procencephalon: forebrain (diencephalon and cerebral hemispheres)

-mesencephalon: midbrain, motor and emotional control

-Rhombencephalon: cerebellum, pons, medulla oblangata

Rhombencephalon

cerebellum, pons, medulla oblangata

mesencephalon

midbrain, motor and emotional control

prosencephalon

forebrain (diencephalon and cerebral hemispheres)

Rhombomeres

formed via rhombencephalon and release transcription factors for neuronal differentiate

Neural crest cells

located dorsal to rhombomeres will give rise to cranial nerves

Hindbrain and spinal cord are patterned by

Hox Genes

Neural tube and its TF: dorsal

form spinal neurons

-PAX3 and PAX7

Neural tube and its TF: ventral

motor neurons

-Nkx6-1

Central neural tube TF

express Pax6

Morphogen gradient on roof plate and notocord

-roof plate: BMP4 and BMP7 (dorsal)

-floor plate: Shh (ventral)

Spinal neurons on dorsal side

-will synapse with peripheral sensory neurons

Shh

induce ventral neural tube structures

-commissural, motor neurons

D1 interneurons

BMP7, dorsalin, activin

D2 interneurons

Dorsalin, activin

V1 and V2 interneurons

low SHH and low TFG-b

motor neurons

high SHH and low TGF-b

Commissural V3 interneurons

high SHH

Cranial placodes

generate the pheripheral neurvous sysem, cranial nerves

neural crest cells also do this

Pre-placodal region

only non-neuronal derivative of the cranial placodes

pre-placodal ectoderm is specified by

Six1/4 and Eya1/2

Lens placode and morphogenesis of the eye

1) optic vesicle formation

2) optic vesicle interacts wiith lens placode —> cells become columnar shape

3) this combination causes the optic cup to form

4) optic cup forms and causes lens internalization

5) lens induces surface ectoderm to become cornea and the neuroectoderm stalk to become optic nerve

6) optic cup forms two layered retina (pigmented and neural retina)

two layers of retina

pigmented retina and neural retina

Surface ectoderm is specified by and become what?

BMPs in the ectoderm

-becomes stratified epidermic

Skin layers

-stratified epidermic

-dermis (mesoderm)

-melanocytes (neural crest)

Dermis

-arise from mesoderm and secretes FGFs and others GF to induce proliferation

Basal layer

generates columns of notch activated cells that differentiate and move through layers

Epidermal placodes

thickening of epidermal ectoderm

-form accessory structures and part of teeth

stages of ectodermal appendages formation

1) placodes: thickening of epidermal

2) budding: ectoderm grows through mesenchyme through intercalation of placode cells

3) morphogenesis: differentiation of ectodermal structures