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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). |