Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Animal embryonic development
open-in-new
<p>In <a href="/facts/Developmental_biology/9dLJhCCv">developmental biology</a>, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an <a href="/facts/Animal/4b8J33nd">animal</a> <a href="/facts/Embryo/9QHnLVLN">embryo</a>. Embryonic development starts with the <a href="/facts/Fertilization/g8u3UKzF">fertilization</a> of an <a href="/facts/Egg_cell/gJyW3W3W">egg cell</a> (ovum) by a <a href="/facts/Sperm/RCxpXygQ">sperm cell</a> (<a href="/facts/Spermatozoon/sTG4GWc0">spermatozoon</a>). Once fertilized, the ovum becomes a single <a href="/facts/Diploid_cell/U8zl4AQe">diploid cell</a> known as a <a href="/facts/Zygote/mSu2xMWA">zygote</a>. The zygote undergoes <a href="/facts/Mitosis/ExxrSUs8">mitotic</a> <a href="/facts/Cell_division/n5MrunWj">divisions</a> with no significant growth (a process known as <a href="/facts/Cleavage_(embryo)/v0osHpJC">cleavage</a>) and <a href="/facts/Cellular_differentiation/bCVqUG7w">cellular differentiation</a>, leading to development of a multicellular embryo after passing through an organizational checkpoint during mid-embryogenesis. In <a href="/facts/Mammal/phSwTzBo">mammals</a>, the term refers chiefly to the early stages of <a href="/facts/Prenatal_development/VpV3S4lu">prenatal development</a>, whereas the terms <a href="/facts/Fetus/evocHd0Y">fetus</a> and <a href="/facts/Fetal_development/VpV3S4lu">fetal development</a> describe later stages. </p><p>The main stages of animal embryonic development are as follows: </p> <ul><li>The <a href="/facts/Zygote/mSu2xMWA">zygote</a> undergoes a series of cell divisions (called cleavage) to form a structure called a morula.</li> <li>The morula develops into a structure called a blastula through a process called <a href="/facts/Blastulation/sJVSBmbH">blastulation</a>.</li> <li>The blastula develops into a structure called a gastrula through a process called <a href="/facts/Gastrulation/kN8X10mK">gastrulation</a>.</li> <li>The gastrula then undergoes further development, including the formation of organs (<a href="/facts/Organogenesis/Wzd0g1al">organogenesis</a>).</li></ul> <p>The embryo then transforms into the next stage of development, the nature of which varies among different animal species (examples of possible next stages include a <a href="/facts/Fetus/evocHd0Y">fetus</a> and a <a href="/facts/Larva/GKo2FIew">larva</a>). </p>