Development: Gastrulation, Neurulation, and Organogenesis (Vocabulary)

A set of vocabulary flashcards covering key concepts from gastrulation, neurulation, and early organogenesis based on the provided lecture notes.

Gastrulation

The early embryonic process during which the three germ layers (ectoderm, mesoderm, endoderm) form; begins around 13 days after fertilization and involves changes in cell motility, shape, and adhesion.

Invagination

A sheet of epithelial cells bends inward to form an inward fold, creating an underlying layer.

Ingression

Individual cells detach from an epithelial sheet and become freely migrating mesenchyme.

Involution

An epithelial sheet rolls inward to form an underlying layer.

Epiboly

A sheet of cells spreads by thinning to cover a larger surface area of the embryo.

Intercalation

Rows of cells move between one another, producing a tissue that is longer and thinner.

Convergent extension

Directional intercalation where cells rearrange to lengthen the tissue along a specific axis.

Primitive streak

A structure that forms during early gastrulation, establishing the body’s anterior-posterior axis and analogous to the Xenopus blastopore.

Blastopore

The opening of the archenteron in amphibian embryos; used as a comparison to the primitive streak in other species.

Anterior-posterior axis

The head-to-tail directional axis established during gastrulation.

Neural plate

Thickened ectoderm that will give rise to the neural tube; induced by signals from the mesoderm.

Neural groove

The invagination of the neural plate forming a groove along the midline.

Neural folds

The raised edges of the neural plate that move toward the midline and fuse to form the neural tube.

Neural tube

The hollow tube formed by fusion of the neural folds; becomes the brain and spinal cord.

Primary neurulation

The process by which the neural plate edges fuse to form the neural tube.

Secondary neurulation

Neural tube formation by hollowing out of a solid precursor.

Neural crest cells

Cells that originate from the neural tube and migrate to various parts of the embryo to form tissues such as peripheral nerves, parts of teeth, and parts of the skull.

Ectoderm

The outer germ layer; gives rise to the nervous system and skin; neural plate is induced from the ectoderm by signals from the mesoderm.

Mesoderm

The middle germ layer; gives rise to muscles, skeleton, circulatory system, somites, notochord, and other structures.

Endoderm

The innermost germ layer; forms the lining of the gut and associated organs.

Somites

Segments of paraxial mesoderm that give rise to vertebrae and associated skeletal muscles.

Notochord

A midline mesodermal structure that induces neural plate formation; contributes to intervertebral discs; largely disappears before birth, with remnants in adult discs.

Cadherins

A family of calcium-dependent transmembrane proteins that mediate cell–cell adhesion and help organize tissues.

E-cadherin

A cadherin type expressed in epithelial cells that maintains epithelial integrity; its expression changes during development.

N-cadherin

A cadherin type expressed in neural and mesenchymal cells, important for neural development and cell migration.

Differential cadherin expression

Variation in cadherin types among tissues guiding cell sorting and tissue organization during neurulation.

Archenteron

The primitive gut formed during gastrulation; will become the digestive tract.

Lateral folds

Embryonic folds that contribute to the formation of the body plan and coelom.

Coelom

The body cavity formed within the mesoderm during organogenesis.

Yolk sac

An extraembryonic membrane that provides early nutrition to the embryo and is connected to the gut via the yolk stalk.

Yolk stalk

The connection between the yolk sac and the midgut, enabling yolk transfer.

Organogenesis

The process by which organs form from the three germ layers during development.

Induction

Signaling interactions where one tissue influences the development of another, such as mesoderm signaling to ectoderm to form the neural plate.