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Category Embryology

First Week of Human Development

Development begins at fertilization when a sperm penetrates an oocyte to form a zygote. A zygote is a highly specialized, totipotent cell, which has the ability to differentiate into any type of cell. It contains chromosomes and genes derived from…

Human Reproduction

Puberty begins when secondary sex characteristics appear, usually between the ages of 10 to 13 years in females and 12 to 14 years in males. Menarche (first menstrual period) may occur as early as 8 years. Puberty in females is…