Placodes: Difference between revisions
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June 2010 "placode development" All (852) Review (90) Free Full Text (285) | June 2010 "placode development" All (852) Review (90) Free Full Text (285) | ||
'''Search Pubmed''' [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=placode%20development placode development] | [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=otic%20placode%20development otic placode development] | [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=optic%20placode%20development optic placode development] | [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=nasal%20placode%20development nasal placode development] | '''Search Pubmed''' [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=placode%20development placode development] | [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=otic%20placode%20development otic placode development] | [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=optic%20placode%20development optic placode development] | [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=nasal%20placode%20development nasal placode development] | [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=Adenohypophyseal%20Placode%20development adenohypophyseal placode development] | ||
| [http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=Adenohypophyseal%20Placode%20development adenohypophyseal placode development] | |||
==External Links== | ==External Links== | ||
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Revision as of 14:19, 15 February 2018
Embryology - 29 Mar 2024 Expand to Translate |
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Introduction
Placodes are ectodermal thickenings which have important roles in development of special sensory systems.
In human development, during week 4 a series of thickened surface ectodermal patches form in pairs rostro-caudally in the head region.
Recent research suggests that all sensory placodes arise from common panplacodal ectoderm (PPE) a horseshoe-shaped region of ectoderm surrounding the anterior neural plate and neural crest. Each placode then differentiates to eventually have different developmental fates. These sensory placodes will later contribute key components of each of our special senses (vision, hearing and smell). Note that their initial postion on the developing head is significantly different to their final position in the future sensory system.
- Adenohypophyseal placode
- Otic placodes - the first placodes visible on the surface of the embryo.
- Olfactory (Nasal) placodes - has 2 components (medial and lateral) and will form the nose olfactory epithelium.
- Optic (Lens) placodes - lies on the surface, adjacent to the outpocketing of the nervous system (which will for the retina) and will form the lens.
- Profundal/trigeminal placodes
Other species have a number of other placodes which form additional sensory structures (fish, lateral line receptor).
- Epibranchial placodes
- Lateral line placodes
- Hypobranchial placodes
Other Placodes? | |
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Note that a second, later developing, form of ectodermal placode development occurs with the development of hair follicles and other integumentary specialisations. This topic does not directly relate to the specialised placodes of the head region covered here. (More? Hair Development | Integumentary_System Development) |
Placode Links: placode | Week 4 | sensory | Otic Placode | Optic Placode | Nasal Placode | Category:Placode | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Some Recent Findings
Movies
Preplacodal DevelopmentPreplacodal development model[9]
(Above text from figure legend[9]) Otic PlacodeThe otic placode is the first of the sensory placodes visible on the surface of the developing human embryo. This placode will differentiate to contribute almost entirely the components of the inner ear. The images below show the first appearance on the embryo surface during week 4 and the eventual disappearance from the surface by week 5. This is only the beginning of the complex development of this structure, influenced by the surrounding epidermis, neural tube and neural crest. Stage 11The scanning EM of the week 4 human embryo Carnegie stage 11 shown below is a superior dorsal view of the paired otic placodes sinking into the surface at the level of the hindbrain between day 24 and day 25. Stage 12By Carnegie stage 12 26 days, only a small opening of the developing otic vesicle (otocyst) remains visible on the embryo surface located behind the second pharyngeal arch. Stage 13By week 5 Carnegie stage 13 the otic vesicle (otocyst) is completely formed and is no longer visible on the embryo surface. Cross-sections of the embryo head at this stage show the otocyst now lies within the embryo as a hollow fluid-filled epithelial "ball", located between the epidermis and the neural tube (hindbrain).
Adenohypophyseal PlacodeThe hypophysis, or pituitary, is an endocrine gland that links the brain to peripheral endocrine organs and systems of the body through several specific hormones. The developmental origin of the hypophysis is unique, with epithelial origins from neural ectoderm (posterior) and from surface ectoderm (anterior) the adenohypophyseal placode.
Drosophila and mouse placode similarity[11]
Olfactory Placodes(Nasal) Optic PlacodesOptic placodes (Lens) lie on the embryo surface, adjacent to the out-pocketing of the nervous system (forms the retina) and will form the lens. surface ectoderm -> lens placode -> lens pit -> lens vesicle -> lens fibres -> lens capsule and embryonic/fetal nucleus.
Trigeminal Placodes(Profundal)
Epibranchial PlacodesEpibranchial ganglia sensory neurons formed by the facial, glossopharyngeal, and vagal placodal regions. These ganglia neurons relay from the sensory organs such as gustatory taste buds, heart baroreceptors, gut sensory enteric nerves.
References
Online Textbooks
ReviewsSchlosser G, Patthey C & Shimeld SM. (2014). The evolutionary history of vertebrate cranial placodes II. Evolution of ectodermal patterning. Dev. Biol. , 389, 98-119. PMID: 24491817 DOI. Patthey C, Schlosser G & Shimeld SM. (2014). The evolutionary history of vertebrate cranial placodes--I: cell type evolution. Dev. Biol. , 389, 82-97. PMID: 24495912 DOI. Graham A & Shimeld SM. (2013). The origin and evolution of the ectodermal placodes. J. Anat. , 222, 32-40. PMID: 22512454 DOI. Schlosser G. (2010). Making senses development of vertebrate cranial placodes. Int Rev Cell Mol Biol , 283, 129-234. PMID: 20801420 DOI. Ladher RK, O'Neill P & Begbie J. (2010). From shared lineage to distinct functions: the development of the inner ear and epibranchial placodes. Development , 137, 1777-85. PMID: 20460364 DOI. Begbie J, Brunet JF, Rubenstein JL & Graham A. (1999). Induction of the epibranchial placodes. Development , 126, 895-902. PMID: 9927591 ArticlesAbitua PB, Gainous TB, Kaczmarczyk AN, Winchell CJ, Hudson C, Kamata K, Nakagawa M, Tsuda M, Kusakabe TG & Levine M. (2015). The pre-vertebrate origins of neurogenic placodes. Nature , 524, 462-5. PMID: 26258298 DOI. Mazet F. (2006). The evolution of sensory placodes. ScientificWorldJournal , 6, 1841-50. PMID: 17205191 DOI. Bhattacharyya S & Bronner-Fraser M. (2004). Hierarchy of regulatory events in sensory placode development. Curr. Opin. Genet. Dev. , 14, 520-6. PMID: 15380243 DOI. Köster RW, Kühnlein RP & Wittbrodt J. (2000). Ectopic Sox3 activity elicits sensory placode formation. Mech. Dev. , 95, 175-87. PMID: 10906460 Search PubmedJune 2010 "placode development" All (852) Review (90) Free Full Text (285) Search Pubmed placode development | otic placode development | optic placode development | nasal placode development | adenohypophyseal placode development External LinksExternal Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.
Glossary Links
Cite this page: Hill, M.A. (2024, March 29) Embryology Placodes. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Placodes
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