Human development (biology)

related topics
{specie, animal, plant}
{disease, patient, cell}
{woman, child, man}
{style, bgcolor, rowspan}
{acid, form, water}
{day, year, event}

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.

Contents

Biological development

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.[by whom?] - meaning Zygote, Embryo, Fetus.

In medicine, the beginning of pregnancy is the instant a sperm cell enters an ovum and forms a viable zygote.[citation needed] Recently,[citation needed] 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 an unborn child helps get the nutrients to the child and helps get rid of the waste from the child. Before the placenta is developed the blastocyst receives its nutrients from the yoke sak which is contained within the blastocyst.

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 universal 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)

Full article ▸

related documents
Sterilization (surgical procedure)
Chest
Nostril
Chitinase
Superfetation
Mycoplasma genitalium
Outer ear
Barr body
Protea cynaroides
Vitaceae
Class (biology)
Hippopotamidae
Gentiana acaulis
Onager
Zosterops
Quetzal
Cecropia
Teosinte
Naraoiidae
Zooplankton
Desmothoracid
Brassicales
Grouse
Pistacia
Zingiberales
Centrarchidae
Musella
Quillback
Magnoliales
Triassic–Jurassic extinction event