Chapter 3 - Embryogenesis and Development Flashcards
Dizygotic (fraternal) twins
Fertilization of 2 different eggs released during one ovulatory cycle by 2 different sperm
Monozygotic (identical) twins
Single zygote splits in 2
Indeterminate cleavage
Results in cells that can still develop into complete organisms
Determinate cleavage
Results in cells with already determined fates
Morula
Solid mass of cells
Blastula
Hollow ball of cells with fluid-filled inner cavity known as a blastocoel
Trophoblast cells
Surround blastocoel and give rise to chorion and placenta
Chorion
Extraembryonic membrane that develops into the placenta
Chorionic Villi
Finger-like projections that penetrate the endometrium
Yolk sac
Supports embryo; site of early blood cell development
Allantosis
Early fluid exchange between embryo and yolk sac
Amnion
Thin, tough membrane filled with amniotic fluid
Gastrula
Characterized by presence of ectoderm, mesoderm, and endoderm
Archenteron
Membrane invagination into blastocoel
Ectoderm
Outermost layer that gives rise to the integument
- Epidermis, hair, nails; epithelia of nose, mouth, and lower anal canal
Mesoderm
Middle layer that develops into different systems
- Musculoskeletal, circulatory, excretory systems
- Gonads
Endoderm
Innermost layer and forms epithelial linings of digestive and respiratory tracts
- Pancreas, thyroid bladder, distal urinary tracts
- Liver
Selective transcription
Only genes needed for that particular cell type are transcribed
Induction
Ability of one group of cells to influence the fate of nearby cells
Cell Specialization
Each cell must perform a specialized function
- 3 stages
Specification
Reversibly designated as a specific cell type
- specialization stage
Determination
Commitment of a cell to a particular function
- specialization stage
Differentiation
Changes that cause the cell to develop into the determined cell type
- specialization stage
Morphogens
Molecules that cause nearby cells to proceed in a specific developmental pathway
