ectoderm of embrylogy somatic

What process forms the 3 germ layers?

Gastrulation

What are the 3 germ layers formed by gastrulation?

Ectoderm, mesoderm, and endoderm

What begins neural induction?

The notochord signals the overlying ectoderm

What does neural induction cause the ectoderm to do?

Thicken and form the neural plate

What is the neural plate?

Thickened ectoderm that will form neural tissue

What happens to the lateral edges of the neural plate?

They elevate to form neural folds

What happens to the middle of the neural plate?

It becomes depressed and forms the neural groove

What are the neural folds?

Raised lateral edges of the neural plate

What is the neural groove?

The depressed middle region between the neural folds

What is neurulation?

The process where the neural plate folds and fuses to form the neural tube

What structure forms when the neural folds fuse?

Neural tube

Where does neural tube closure begin?

Cervical region

How does neural tube closure progress?

Cranially and caudally like a zipper

What are the anterior and posterior neuropores?

Temporary open ends of the neural tube

What do the neuropores communicate with before closure?

Amniotic cavity

When is neurulation complete?

When the neuropores close

What does the cephalic part of the neural tube form?

Brain

What does the more caudal neural tube form?

Spinal cord

What does BMP4 cause ectoderm to become?

Epidermis

What pathway does BMP4 promote?

Epidermal or non-neural ectoderm

What does FGF do to BMP4?

Represses BMP4

What happens when FGF represses BMP4?

Ectoderm can become neural tissue and form the neural plate

What pathway does FGF promote?

Neural tissue and neural plate formation

What are neural crest cells?

Multipotent cells that break away from the lateral edges of the neural folds

When do neural crest cells begin to break away?

Before the neural folds completely fuse

Where do neural crest cells migrate after leaving the neural folds?

Into the underlying mesoderm

Do neural crest cells become mesoderm when they migrate into it?

No, they remain ectoderm-derived neural crest cells

Why are neural crest cells sometimes called the fourth germ layer?

They migrate widely and form many different tissues

What 2 pathways can trunk neural crest cells follow?

Dorsal pathway and ventral pathway

What does the dorsal trunk neural crest pathway form?

Melanocytes in skin and hair follicles

What does the ventral trunk neural crest pathway form?

Sensory ganglia, sympathetic and enteric neurons, Schwann cells, and adrenal medulla cells

What is a major nervous system derivative of neural crest cells?

Most of the PNS

What are major neural ectoderm derivatives?

CNS and PNS

What sensory structures are listed as ectoderm derivatives?

Sensory epithelium of the ear, nose, and eye

What surface structures are ectoderm derivatives?

Epidermis, hair, and nails

What glands are listed as ectoderm derivatives?

Subcutaneous glands and mammary glands

What other structures are listed as ectoderm derivatives?

Pituitary gland and enamel of the teeth

What is the otic placode?

A thickened ectodermal region that develops into structures of the inner ear

What is the lens placode?

A thickened ectodermal region that develops into the lens of the eye

What is the ectoderm neural-development sequence?

Neural induction, neural plate, neural folds and groove, neurulation, neural tube, neural crest migration

What is the full story starting with gastrulation?

Gastrulation, 3 germ layers, notochord signaling, neural plate, neural folds and groove, neural tube, neural crest cells