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From Wikipedia, the free encyclopedia

Human development is the process of growing to maturity. In biological terms, this entails growth from a one-celled zygote to an adult human being.


Biological development

Sperm fertilizing an egg

Development begins with fertilization, the process by which the male gamete, the sperm cell, and the female gamete, the egg, fuse to produce a zygote. In pregnancy the 3 stages are commonly referred as Z.E.F. - meaning Zygote, Embryo, Fetus.

In medicine, the beginning of pregnancy is the instant a sperm cell enters an ovum and forms a viable zygote. Recently, in western medicine, pregnancy is defined as beginning when a zygote becomes implanted in a woman's uterus. This occurs when the zygote then becomes embedded into the endometrium (lining of the uterus) where it forms a placenta, for the purpose of receiving essential nutrients through the uterus wall. The umbilical cord in a newborn child helps get the nutrients to the child and helps get rid of the waste from the child.

The zygote undergoes rapid cell divisions with no significant growth (a process known as cleavage) and cellular differentiation, leading to development of an embryo.

Childbirth is the process in which the baby is born. Age is defined relative to this event in most cultures.

Physical stages of human life

There are no universally unanimous definitions for terms of age-related physical development stages, but following are some approximate age ranges:

  • Prenatal (fertilization - birth)
    • Embryo - (fertilization - 8 weeks of gestational phase)
      • Zygote, the point of conception, fertilization
      • Blastocyst the period between conception and embryonic stages
      • Embryo; the embryonic period starts at three weeks and continues until the end of the 8th week of pregnancy
    • Fetus (8 weeks of gestational phase - birth)
Approximate outline of development periods in child development.

Also sometimes used are terms that specify one's age in numbers, such as:

Physical development milestones

Note: the Tanner stages can be used to approximately judge a child's age based on physical development.

See also


  1. ^ Growth of Asthmatic Children Before Long-Term Treatment with Inhaled Corticosteroids T. Moudiou‌, D. Theophilatou‌, K. Priftis‌ and A. Papadimitriou, M.D. Journal of Asthma. 2003, Vol. 40, No. 6, Pages 667-671.
  2. ^ a b Jaffe-Campanacci Syndrome. A Case Report and Review of the Literature. Mohammad Anwar Hau, MBBS, MMed (Ortho), Edward J. Fox, MD, Justin M. Cates, MD, PhD, Brian E. Brigman, MD and Henry J. Mankin, MD. The Journal of Bone and Joint Surgery (American) 84:634-638 (2002)
  3. ^ Persistent osteopenia in adolescent idiopathic scoliosis (AIS) – Factors predisposing to generalized osteopenia, a cross-sectional and longitudinal investigation Warren T.K. Leea, C.S.K. Cheunga, Y.K. Tsec, W.W. Chaua, L. Qina and Jack C.Y. Chenga. doi:10.1016/j.ics.2006.08.003

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