The “default fate” of the ectoderm is to become neural tissue

TLS Online TPP Program

#Id: 1035

#Unit 5. Developmental Biology

In mammals, secondary neurulation begins at the level of the sacral vertebrae of the tail.

TLS Online TPP Program

#Id: 1036

#Unit 5. Developmental Biology

Junctional neurulation 

combination of mechanisms involved in both primary and secondary neurulation

TLS Online TPP Program

#Id: 1037

#Unit 5. Developmental Biology

Primary neurulation can be divided into four stages:

1. Elongation and folding of the neural plate

2. Bending of the neural plate

3. Convergence of the neural folds

4. Closure of the neural tube

TLS Online TPP Program

#Id: 1038

#Unit 5. Developmental Biology

Anencephaly 

a failure of the anterior (rostral) portion of the embryonic neural tube (anterior neuropore) to close properly.

OR

a failure to close the neural tube allows the forebrain to remain in contact with amniotic fluid and subsequently degenerate.

TLS Online TPP Program

#Id: 1039

#Unit 5. Developmental Biology

Craniorachischisis-combination of anencephaly with a contiguous bony defect of the spine (also without meninges covering the neural tissue –rachischisis)

TLS Online TPP Program

#Id: 1040

#Unit 5. Developmental Biology

The first visible sign of limb development is the formation of bilateral bulges called limb buds.

1. limb bud  is