Organogenesis

'''Organogenesis''' is the phase of [[embryogenesis|embryonic development]] that starts at the end of [[gastrulation]] and continues until [[birth]]. During organogenesis, the three [[germ layer]]s formed from gastrulation (the [[ectoderm]], [[endoderm]], and [[mesoderm]]) form the tissues and [[Organ (biology)#Viscera|internal organ]]s of the organism.{{cite journal |last1=Gilbert|first1=S. F. |last2=Barresi|first2=M. J. F. |title=Developmental Biology, 11Th Edition 2016 |date=2017-05-01|journal=American Journal of Medical Genetics Part A|volume=173|issue=5|page=1430|doi=10.1002/ajmg.a.38166 |issn = 1552-4833 }} [[Image:Germ layers.jpg|thumb|590x590px|The [[endoderm]] of [[vertebrates]] produces tissue within the [[lung]]s, [[thyroid]], and [[pancreas]]. The [[mesoderm]] aids in the production of [[cardiac muscle]], [[skeletal muscle]], [[smooth muscle]], tissues within the [[kidney]]s, and [[red blood cell]]s. The [[ectoderm]] produces tissues within the [[Epidermis (skin)|epidermis]] and aids in the formation of [[neuron]]s within the brain, and [[melanocytes]].]]

'''Organogenesis''' is the phase of [[embryogenesis|embryonic development]] that starts at the end of [[gastrulation]] and continues until [[birth]]. During organogenesis, the three [[germ layer]]s formed from gastrulation (the [[ectoderm]], [[endoderm]], and [[mesoderm]]) form the tissues and [[Organ (biology)#Viscera|internal organ]]s of the organism.{{cite journal |last1=Gilbert|first1=S. F. |last2=Barresi|first2=M. J. F. |title=Developmental Biology, 11Th Edition 2016 |date=2017-05-01|journal=American Journal of Medical Genetics Part A|volume=173|issue=5|page=1430|doi=10.1002/ajmg.a.38166 |issn = 1552-4833 }} [[Image:Germ layers.jpg|thumb|590x590px|The [[endoderm]] of [[vertebrates]] produces tissue within the [[lung]]s, [[thyroid]], and [[pancreas]]. The [[mesoderm]] aids in the production of [[cardiac muscle]], [[skeletal muscle]], [[smooth muscle]], tissues within the [[kidney]]s, and [[red blood cell]]s. The [[ectoderm]] produces tissues within the [[Epidermis (skin)|epidermis]] and aids in the formation of [[neuron]]s within the brain, and [[melanocytes]].]]

The cells of each of the three germ layers undergo [[Cellular differentiation|differentiation]], a process where less-specialized cells become more-specialized through the expression of a specific set of genes. Cell differentiation is driven by cell signaling cascades.{{Cite journal|last=Rankin|first=Scott|date=2018|title=Timing is everything: Reiterative Wnt, BMP and RA signaling regulate developmental competence during endoderm organogenesis|journal=Developmental Biology|volume=434|issue=1|pages=121–132|via=NCBI|doi=10.1016/j.ydbio.2017.11.018|pmc=5785443|pmid=29217200}} Differentiation is influenced by [[Juxtacrine signalling|juxtacrine]], [[Paracrine signaling|paracrine]], and [[Autocrine signaling|autocrine]] signaling. Juxtacrine signaling is exchanged between adjacent cells. Paracrine signals are sent by one cell and received by neighboring cells over short distances. Autocrine signaling is due to intracellular signals being produced and received by the same cell. These signaling pathways allow for cell rearrangement and ensure that organs form at specific sites within the organism at the correct time during development. The organogenesis process can be studied using embryos and [[Organoid|organoids]].{{Cite journal|last1=Ader|first1=Marius|last2=Tanaka|first2=Elly M|title=Modeling human development in 3D culture|journal=Current Opinion in Cell Biology|volume=31|pages=23–28|doi=10.1016/j.ceb.2014.06.013|pmid=25033469|year=2014}}

The cells of each of the three germ layers undergo [[Cellular differentiation|differentiation]], a process where less-specialized cells become more-specialized through the expression of a specific set of genes. Cell differentiation is driven by cell signaling cascades.{{Cite journal|last=Rankin|first=Scott|date=2018|title=Timing is everything: Reiterative Wnt, BMP and RA signaling regulate developmental competence during endoderm organogenesis|journal=Developmental Biology|volume=434|issue=1|pages=121–132|via=NCBI|doi=10.1016/j.ydbio.2017.11.018|pmc=5785443|pmid=29217200}} Differentiation is influenced by [[Juxtacrine signalling|juxtacrine]], [[Paracrine signaling|paracrine]], and [[Autocrine signaling|autocrine]] signaling. Juxtacrine signaling is exchanged between adjacent cells. Paracrine signals are sent by one cell and received by neighboring cells over short distances. Autocrine signaling is due to intracellular signals being produced and received by the same cell. These signaling pathways allow for cell rearrangement and ensure that organs form at specific sites within the organism at the correct time during development. The organogenesis process can be studied using embryos of various model organisms like [[zebrafish]], [[xenopus]], [[Chicken|chickens]], and [[Mouse|mice]]. Studying human embryos is difficult and faces ethical concerns, but can be done using organoids developed in vitro without the use of a human embryo. [[Organoid|Organoids]] are simplified organ structures made from adult stem cells, embryonic stem cells, or [[Induced pluripotent stem cell|induced pluripotent stem cells]]. These stem cells differentiate into various organs due to interactions with other cells or the matrix they are grown on.

== Organs produced by the germ layers ==

== Organs produced by the germ layers ==