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Biology
Human Development
| Term | Definition |
|---|---|
| Ovulation | The release of a mature egg from the ovary into one of the Fallopian tubes. |
| Fertilization | The fusion of a sperm and egg cell. *Only one sperm cell can successfully break through the egg's protective barrier. |
| Zygote | A fertilized egg. An embryo is formed. |
| Cleavage or Mitosis | Cellular division occuring over 6 to 7 days. cells double in number and decrease in size. |
| Blastocyst | A hollow ball of cells (approximatley 64 cells). |
| Implantation | When the blastocyst attaches to the wall of the uterus and begins to grow into the tissues of the mother. |
| Differentiation | The process in which cells become specialized in structure and function. |
| Gastrulation | Cell migration and development resulting in the formation of 3 cell-germ layers: ectoderm, endoderm, and mesoderm |
| Ectoderm | Outer-most germ layer; will develop into the skin and nervous system. |
| Endoderm | Inner-most germ layer; will develop into organs of the digestive system and respiratory system. |
| Mesoderm | Middle germ layer; will develop into muscles, bones, blood cells, and gonads. |
| Neurulation | The first step in the development of the nervous system; the ectoderm layer develops into the brain and spinal cord. |
| Placenta | The connecting organ between mother and embryo; source of respiration nourishment and excretion for the embryo |
| Embryo | Early development stage of a multicellular organism. |
| Fetus | A human embryo after 8 weeks of development (2 months). |