Organogenesis Flashcards
Gastrulation at day 18
Neural plate is formed
- consists of tall columnar cells (becomes the epidermis)
Gastrulation at day 25
Primitive streak disappears
What happens during the 4th week?
The germ disc is transformed into something that looks more like a body
- embryo folds into a 3D structure which initiates the formation of organs
When does organogenesis take place?
4th-8th week
After 8 weeks it is considered a fetus
Anencephaly
Caused by the failure of the anterior neuropore to close. This is always fatal
Craniorachischisis
Failure of the entire neural tube to close. Fatal
Spina Bifida
Caused by failure of the posterior neuropore to close. Can cause paralysis or less serious issues
What type of factors are secreted by the cells of the organizer to assure that dorsal ectodermal cells assume a neural rather than an epidermal fate?
BMP inhibitors
What are the three major domains that are formed from the ectoderm
the surface ectoderm (primarily epidermis)
the neural crest (peripheral neurons, pigment, facial cartilage)
the neural tube (brain and spinal cord)
Neural Plate
Portion of the ectoderm that forms the brain and the spinal cord
Neurulation
Process of forming the neural tube from the neural plate
Primary Neurulation
When the neural tube is formed by invagination and pinching off (epithelial). Head to tail direction so the anterior neuropore closes first and the posterior one closes last
Secondary Neurulation
When the neural tube is formed by coalescence of mesenchymal cells to form a rod followed by cavitation to in order to form a tube. Only occurs at the posterior end of the animal
Junctional Neurulation
The transition zone between primary and secondary neurulation. Both primary and secondary are occurring in the same piece
Medial Hinge Point (MHP)
Anchored to to notochord (allows lateral cells to rise)
