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{{About|the part of the face}}
{{About|the part of the face}}<br />
[[File:Crane3chin.png|thumb|Photo showing the human chin]]
{{Infobox anatomy
The '''human''' '''chin''' (also known as the mental protuberance, mental eminence, and rarely mental osseum, tuber symphyseos) refers to the forward pointed part of the anterior [[mandible]] (mental region) which is the area below the lower [[lip]] (see photo on the left top corner).
| Name = Chin
| Latin = Mentum
| Greek =
| Image = File:Mental region (chin).png
| Caption = Chin or mental region labeled in purple
| Width =
| Image2 =
| Caption2 =
| Precursor =
| System =
| Artery = [[Inferior alveolar artery]]
| Vein =
| Nerve = [[Mental nerve]]
| Lymph =
}}
The '''chin''' or the '''mental region''' is the area of the [[face]] below the lower [[lip]] and including the [[mandibular prominence]].<ref>{{cite web|title=Full Definition of chin|publisher=[[Merriam-Webster]] Dictionary|accessdate=2015-09-22|url=http://www.merriam-webster.com/dictionary/chin}}</ref><ref>{{cite book|last=O'Loughlin|first=Michael McKinley, Valerie Dean|title=Human anatomy|year=2006|publisher=McGraw-Hill Higher Education|location=Boston|isbn=0-07-249585-5|pages=400–01}}</ref> It is formed by the lower front of the [[Human mandible|mandible]].


==Evolution==
===Evolution===
The presence of well-developed chin is considered as one of the unique morphological characters of ''[[Homo sapiens]]'' that differentiates them from other human ancestors including the closely related [[Neanderthal|Neanderthals]].<ref>{{Cite book|title=The origin of anatomically modern humans in western Europe. In F. H. Smith & Spencer (Eds.), The origins of modern humans: a world survey of the fossil evidence|last=Stringer, C. B., Hublin, J.-J., & Vandermeersch, B.|first=|publisher=|year=1984|isbn=|location=New York|pages=51–135}}</ref><ref>{{Cite journal|last=Schwartz|first=Jeffrey H.|last2=Tattersall|first2=Ian|date=2000-3|title=The human chin revisited: what is it and who has it?|url=https://linkinghub.elsevier.com/retrieve/pii/S0047248499903391|journal=Journal of Human Evolution|language=en|volume=38|issue=3|pages=367–409|doi=10.1006/jhev.1999.0339}}</ref> Early human ancestors have varied symphysial morphology but none of them have a well-developed chin. So, why do modern humans own this pointed morphology and why it is not present in any [[fossil]] or living [[Primate|primates]] remained tantalizing question. Although the origin of chin is traditionally associated with the anterior-posterior breadth shortening of the dental arch or tooth row its general mechanical or functional advantage during feeding, the developmental origin, its link with the human speech, physiology, and social influence remained highly debated. Nowadays, scientists are tackling this question to know the functional advantage of having chin and its developmental origin.
Pointed chins are specific to modern humans; even very closely related species, such as Neanderthals, did not have them. The reasons for this adaptation are unclear, but a few explanations have been proposed.


==== Functional perspectives ====
Nathan Holton of the University of Iowa states, "In some ways, it seems trivial, but a reason why chins are so interesting is we’re the only ones who have them."<ref name="sciencedaily.com">University of Iowa. (2015, April 13). Why we have chins: Our chin comes from evolution, not mechanical forces. ScienceDaily. Retrieved July 28, 2018 from www.sciencedaily.com/releases/2015/04/150413183745.htm</ref> New research done by Holton shows that the evolution of this unique characteristic was formed, not by mechanical forces such as chewing, but perhaps from evolutionary adaptations involving face size and shape. Holton claims that this evolutionary adaptation occurred as our face became smaller compared to the Neanderthal-era human beings; the modern human head is approximately 15% shorter. Therefore through the change in size the chin became a factor that balanced the shape of the face.
Robinson (1913)<ref>{{Cite journal|last=Robinson|first=L.|date=1913|title=The story of the chin|url=|journal=Knowledge|volume=36|pages=410–420|via=}}</ref> suggested that the demand to resist masticatory stresses triggered bone thickening in the mental region of the mandible and ultimately formed prominent chin. Moreover, Daegling (1993)<ref>{{Cite journal|last=Daegling|first=David J.|date=1993|title=Functional morphology of the human chin|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/evan.1360010506|journal=Evolutionary Anthropology: Issues, News, and Reviews|language=en|volume=1|issue=5|pages=170–177|doi=10.1002/evan.1360010506|issn=1520-6505}}</ref> explained the chin as functional adaptation to resist masticatory stress that causes vertical bending stresses in the coronal plane.  Others have argued the prominent chin is adapted to resisting wishboning forces,<ref>{{Cite book|title=The Adaptive Chin|last=DuBrul EL, Sicher H|first=|publisher=Springfield, IL: C.C. Thomas.|year=1954|isbn=|location=|pages=}}</ref> dorso-ventral shear forces, and generally a mechanical advantage to resist lateral transverse bending and vertical bending in the coronal plane<ref>{{Cite journal|last=Gröning|first=Flora|last2=Liu|first2=Jia|last3=Fagan|first3=Michael J.|last4=O'Higgins|first4=Paul|date=2011-4|title=Why do humans have chins? Testing the mechanical significance of modern human symphyseal morphology with finite element analysis|url=http://doi.wiley.com/10.1002/ajpa.21447|journal=American Journal of Physical Anthropology|language=en|volume=144|issue=4|pages=593–606|doi=10.1002/ajpa.21447}}</ref>. In contrary, others<ref>{{Cite journal|last=Ichim|first=I.|last2=Swain|first2=M.|last3=Kieser|first3=J.A.|date=2006-07|title=Mandibular Biomechanics and Development of the Human Chin|url=https://doi.org/10.1177/154405910608500711|journal=Journal of Dental Research|language=en-US|volume=85|issue=7|pages=638–642|doi=10.1177/154405910608500711|issn=0022-0345}}</ref> have suggested that the presence of chin is not related with mastication. So, does the presence of thick bone in the relatively small mandible indicates better force resistance capacity? Is chin adaptive or nonadaptive structure? How do we say that modern ''Homo sapiens'' with reduced tooth size and with high behavioral dependence and food processing behavior require masticatory resistant bone? All these and many other mechanical and functional tantalizing questions remained highly debated.


==== Developmental perspectives ====
⚫
Research on the evolution of the chin was further continued by the University of Iowa through another perspective. Opposing to Holtons scientific methods of the examination of the evolution of the chin, Robert Franciscus tackled the issue through an anthropological lens. Franciscus believed that the evolution of the chin was formed as a consequence of the change in lifestyle that was seen in human beings approximately 80,000 years ago. This was an era when human beings started to communicate more, turning their [[hunter-gatherer]] societies into agricultural societies where they increased their social networks. This decreased territorial disputes, as it further incentified the building of alliances in order to exchange goods and belief systems. Franciscus then believed that this change in the human environment reduced hormone levels, especially in men, resulting in the natural adaptation of the evolution of the chin.<ref name="sciencedaily.com"/>
Recent works on the developmental morphological changes of the mandible <ref>{{Cite journal|last=Coquerelle|first=Michael|last2=Bookstein|first2=Fred L.|last3=Braga|first3=José|last4=Halazonetis|first4=Demetrios J.|last5=Weber|first5=Gerhard W.|date=2010-11|title=Fetal and infant growth patterns of the mandibular symphysis in modern humans and chimpanzees (Pan troglodytes): Human and chimpanzee mandibles|url=http://doi.wiley.com/10.1111/j.1469-7580.2010.01287.x|journal=Journal of Anatomy|language=en|volume=217|issue=5|pages=507–520|doi=10.1111/j.1469-7580.2010.01287.x|pmc=PMC3035859|pmid=20807267}}</ref><ref name=":0">{{Cite journal|last=Coquerelle|first=Michael|last2=Prados-Frutos|first2=Juan Carlos|last3=Rojo|first3=Rosa|last4=Mitteroecker|first4=Philipp|last5=Bastir|first5=Markus|date=2013-11-15|editor-last=Frayer|editor-first=David|title=Short Faces, Big Tongues: Developmental Origin of the Human Chin|url=https://dx.plos.org/10.1371/journal.pone.0081287|journal=PLoS ONE|language=en|volume=8|issue=11|pages=e81287|doi=10.1371/journal.pone.0081287|issn=1932-6203|pmc=PMC3829973|pmid=24260566}}</ref><ref name=":1">{{Cite journal|last=Coquerelle|first=Michael|last2=Prados-Frutos|first2=Juan Carlos|last3=Rojo|first3=Rosa|last4=Drake|first4=Abby Grace|last5=Murillo-Gonzalez|first5=Jorge Alfonso|last6=Mitteroecker|first6=Philipp|date=2017-9|title=The Fetal Origin of the Human Chin|url=http://link.springer.com/10.1007/s11692-017-9408-9|journal=Evolutionary Biology|language=en|volume=44|issue=3|pages=295–311|doi=10.1007/s11692-017-9408-9|issn=0071-3260}}</ref> have shown that the human chin or at least the inverted-T shaped mental region develops during prenatal (before birth) but the chin become prominent during early postnatal (after birth). This later modification happens by [[bone remodeling]] processes ([[bone resorption]] and [[Bone resorption|bone deposition]])<ref name=":2">{{Cite book|title=Facial growth. 3rd edition|last=D. H|first=Enlow|publisher=Philadelphia: Saunders|year=1990|isbn=|location=|pages=}}</ref>. Coquerelle et al.<ref name=":0" /><ref name=":1" /> show that the anteriorly positioned cervical column of the spine and forward displacement of the hyoid bone created anterior-posterior breadth space limitation in the oral cavity for tongue, and laryngeal and [[Suprahyoid muscles|suprahyoid]] musculatures. Accordingly, this leads the upper parts of the mandible (alveolar process) to retract posteriorly, following the posterior movement of the upper tooth row, while the basal part of the symphysis remained protruded to create more space, and thereby creating the inverted-T shaped mental relief during early ages and prominent chin later. The alveolar region (superior part of the symphysis) is sculpted by bone resorption field but the chin (basal or inferior part) is depository in its nature<ref name=":2" />. These coordinated bone growth snd modeling processes molded the vertical shaped human symphysis during birth into posteriorly receding and the chin becomes prominent.  



⚫
Overall, human beings are unique in the sense that they are the only species among hominids who have chins. In the novel, ''The Enduring Puzzle of the Human Chin'', evolutionary anthropologists, James Pampush and David Daegling discuss various theories that have been raised to solve the puzzle of the chin.
Recent research on the ontogeny of chin<ref name=":3">{{Cite journal|last=Holton|first=N. E.|last2=Bonner|first2=L. L.|last3=Scott|first3=J. E.|last4=Marshall|first4=S. D.|last5=Franciscus|first5=R. G.|last6=Southard|first6=T. E.|date=2015|title=The ontogeny of the chin: an analysis of allometric and biomechanical scaling|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/joa.12307|journal=Journal of Anatomy|language=en|volume=226|issue=6|pages=549–559|doi=10.1111/joa.12307|issn=1469-7580|pmc=PMC4450959|pmid=25865897}}</ref> shows that the evolution of this unique characteristic was formed, not by mechanical forces such as chewing, but perhaps from evolutionary adaptations involving face size reduction and shape change. They claims that this evolutionary adaptation occurred as our face became smaller compared to other contemporaneous human beings.
==== Other Perspectives ====
⚫
Opposing to Holtons<ref name=":3" /> investigation of the evolution of the chin, Robert Franciscus tackled the issue through an anthropological lens. Franciscus believed that the evolution of the chin was formed as a consequence of the change in lifestyle that was seen in human beings approximately 80,000 years ago. This was an era when human beings started to communicate more, turning their [[hunter-gatherer]] societies into agricultural societies where they increased their social networks. This decreased territorial disputes, as it further incentified the building of alliances in order to exchange goods and belief systems. Franciscus then believed that this change in the human environment reduced hormone levels, especially in men, resulting in the natural adaptation of the evolution of the chin.<ref name="sciencedaily.com">University of Iowa. (2015, April 13). Why we have chins: Our chin comes from evolution, not mechanical forces. ScienceDaily. Retrieved July 28, 2018 from www.sciencedaily.com/releases/2015/04/150413183745.htm</ref>

⚫
Overall, human beings are unique in the sense that they are the only species among [[Primate|primates]] who have chins. In the novel, ''The Enduring Puzzle of the Human Chin'', evolutionary anthropologists, James Pampush and David Daegling discuss various theories that have been raised to solve the puzzle of the chin.
They conclude that, "Each of the proposals we have discussed falter either empirically or theoretically; some fail, to a degree, on both accounts… This should serve as motivation, not discouragement, for researchers to continue investigating this modern human peculiarity… perhaps understanding the chin will reveal some unexpected insight into what it means to be human."<ref>Gauger Ann. (2016, February 11) On the origin of Chins. Evolution News. Retrieved July 28, 2018 from https://evolutionnews.org/2016/02/on_the_origin_o_8/</ref>
They conclude that, "Each of the proposals we have discussed falter either empirically or theoretically; some fail, to a degree, on both accounts… This should serve as motivation, not discouragement, for researchers to continue investigating this modern human peculiarity… perhaps understanding the chin will reveal some unexpected insight into what it means to be human."<ref>Gauger Ann. (2016, February 11) On the origin of Chins. Evolution News. Retrieved July 28, 2018 from https://evolutionnews.org/2016/02/on_the_origin_o_8/</ref>
Through the examination of various theories that are constantly being formed, the truth about the origins of the human chin will perhaps be unraveled in the close future.
Through the examination of various theories that are constantly being formed, the truth about the origins of the human chin will perhaps be unraveled in the close future.

Revision as of 17:38, 19 November 2019

This article is about the part of the face. For other uses, see Chin (disambiguation).


Photo showing the human chin

The human chin (also known as the mental protuberance, mental eminence, and rarely mental osseum, tuber symphyseos) refers to the forward pointed part of the anterior mandible (mental region) which is the area below the lower lip (see photo on the left top corner).

Evolution

The presence of well-developed chin is considered as one of the unique morphological characters of Homo sapiens that differentiates them from other human ancestors including the closely related Neanderthals.[1][2] Early human ancestors have varied symphysial morphology but none of them have a well-developed chin. So, why do modern humans own this pointed morphology and why it is not present in any fossil or living primates remained tantalizing question. Although the origin of chin is traditionally associated with the anterior-posterior breadth shortening of the dental arch or tooth row its general mechanical or functional advantage during feeding, the developmental origin, its link with the human speech, physiology, and social influence remained highly debated. Nowadays, scientists are tackling this question to know the functional advantage of having chin and its developmental origin.

Functional perspectives

Robinson (1913)[3] suggested that the demand to resist masticatory stresses triggered bone thickening in the mental region of the mandible and ultimately formed prominent chin. Moreover, Daegling (1993)[4] explained the chin as functional adaptation to resist masticatory stress that causes vertical bending stresses in the coronal plane.  Others have argued the prominent chin is adapted to resisting wishboning forces,[5] dorso-ventral shear forces, and generally a mechanical advantage to resist lateral transverse bending and vertical bending in the coronal plane[6]. In contrary, others[7] have suggested that the presence of chin is not related with mastication. So, does the presence of thick bone in the relatively small mandible indicates better force resistance capacity? Is chin adaptive or nonadaptive structure? How do we say that modern Homo sapiens with reduced tooth size and with high behavioral dependence and food processing behavior require masticatory resistant bone? All these and many other mechanical and functional tantalizing questions remained highly debated.

Developmental perspectives

Recent works on the developmental morphological changes of the mandible [8][9][10] have shown that the human chin or at least the inverted-T shaped mental region develops during prenatal (before birth) but the chin become prominent during early postnatal (after birth). This later modification happens by bone remodeling processes (bone resorption and bone deposition)[11]. Coquerelle et al.[9][10] show that the anteriorly positioned cervical column of the spine and forward displacement of the hyoid bone created anterior-posterior breadth space limitation in the oral cavity for tongue, and laryngeal and suprahyoid musculatures. Accordingly, this leads the upper parts of the mandible (alveolar process) to retract posteriorly, following the posterior movement of the upper tooth row, while the basal part of the symphysis remained protruded to create more space, and thereby creating the inverted-T shaped mental relief during early ages and prominent chin later. The alveolar region (superior part of the symphysis) is sculpted by bone resorption field but the chin (basal or inferior part) is depository in its nature[11]. These coordinated bone growth snd modeling processes molded the vertical shaped human symphysis during birth into posteriorly receding and the chin becomes prominent.  


Recent research on the ontogeny of chin[12] shows that the evolution of this unique characteristic was formed, not by mechanical forces such as chewing, but perhaps from evolutionary adaptations involving face size reduction and shape change. They claims that this evolutionary adaptation occurred as our face became smaller compared to other contemporaneous human beings.

Other Perspectives

Opposing to Holtons[12] investigation of the evolution of the chin, Robert Franciscus tackled the issue through an anthropological lens. Franciscus believed that the evolution of the chin was formed as a consequence of the change in lifestyle that was seen in human beings approximately 80,000 years ago. This was an era when human beings started to communicate more, turning their hunter-gatherer societies into agricultural societies where they increased their social networks. This decreased territorial disputes, as it further incentified the building of alliances in order to exchange goods and belief systems. Franciscus then believed that this change in the human environment reduced hormone levels, especially in men, resulting in the natural adaptation of the evolution of the chin.[13]

Overall, human beings are unique in the sense that they are the only species among primates who have chins. In the novel, The Enduring Puzzle of the Human Chin, evolutionary anthropologists, James Pampush and David Daegling discuss various theories that have been raised to solve the puzzle of the chin. They conclude that, "Each of the proposals we have discussed falter either empirically or theoretically; some fail, to a degree, on both accounts… This should serve as motivation, not discouragement, for researchers to continue investigating this modern human peculiarity… perhaps understanding the chin will reveal some unexpected insight into what it means to be human."[14] Through the examination of various theories that are constantly being formed, the truth about the origins of the human chin will perhaps be unraveled in the close future.

Cleft chin

Example of a cleft chin (William McKinley)
Human jaw front view

The terms cleft chin,[15] chin cleft,[15][16] dimple chin,[17][18] or chin dimple,[15] refer to a dimple on the chin. It is a Y-shaped fissure on the chin with an underlying bony peculiarity.[19] Specifically, the chin fissure follows the fissure in the lower jaw bone that resulted from the incomplete fusion of the left and right halves of the jaw bone, or muscle, during the embryonal and fetal development. For other individuals, it can develop over time, often because one half of the jaw is longer than the other, leading to facial asymmetry.[15]

A cleft chin is an inherited trait in humans, where the recessive gene, and incomplete dominance, can causes the cleft chin. However, it is also a classic example for variable penetrance[20] with environmental factors or a modifier gene possibly affecting the phenotypical expression of the actual genotype. Cleft chins can be presented in a child when neither parent presents a cleft chin. Cleft chins are common among people originating from Europe, the Middle East and South Asia.[21]

In Persian literature, the chin dimple is considered a factor of beauty, and is metaphorically referred to as "the chin pit" or "the chin well": a well in which the poor lover is fallen and trapped.[22]

Double chin

Drawing circa 1900 depicting Joseph Urban as having a double chin

A double chin is a layer of subcutaneous fat around the neck that sags down and creates a wrinkle, creating the appearance of a second chin. This fat pad is sometimes surgically removed and the corresponding muscles under the jaw shortened.[23]

See also

References

  1. ^ Stringer, C. B., Hublin, J.-J., & Vandermeersch, B. (1984). The origin of anatomically modern humans in western Europe. In F. H. Smith & Spencer (Eds.), The origins of modern humans: a world survey of the fossil evidence. New York. pp. 51–135.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: multiple names: authors list (link)
  2. ^ Schwartz, Jeffrey H.; Tattersall, Ian (2000-3). "The human chin revisited: what is it and who has it?". Journal of Human Evolution. 38 (3): 367–409. doi:10.1006/jhev.1999.0339. {{cite journal}}: Check date values in: |date= (help)
  3. ^ Robinson, L. (1913). "The story of the chin". Knowledge. 36: 410–420.
  4. ^ Daegling, David J. (1993). "Functional morphology of the human chin". Evolutionary Anthropology: Issues, News, and Reviews. 1 (5): 170–177. doi:10.1002/evan.1360010506. ISSN 1520-6505.
  5. ^ DuBrul EL, Sicher H (1954). The Adaptive Chin. Springfield, IL: C.C. Thomas.
  6. ^ Gröning, Flora; Liu, Jia; Fagan, Michael J.; O'Higgins, Paul (2011-4). "Why do humans have chins? Testing the mechanical significance of modern human symphyseal morphology with finite element analysis". American Journal of Physical Anthropology. 144 (4): 593–606. doi:10.1002/ajpa.21447. {{cite journal}}: Check date values in: |date= (help)
  7. ^ Ichim, I.; Swain, M.; Kieser, J.A. (2006-07). "Mandibular Biomechanics and Development of the Human Chin". Journal of Dental Research. 85 (7): 638–642. doi:10.1177/154405910608500711. ISSN 0022-0345. {{cite journal}}: Check date values in: |date= (help)
  8. ^ Coquerelle, Michael; Bookstein, Fred L.; Braga, José; Halazonetis, Demetrios J.; Weber, Gerhard W. (2010-11). "Fetal and infant growth patterns of the mandibular symphysis in modern humans and chimpanzees (Pan troglodytes): Human and chimpanzee mandibles". Journal of Anatomy. 217 (5): 507–520. doi:10.1111/j.1469-7580.2010.01287.x. PMC 3035859. PMID 20807267. {{cite journal}}: Check date values in: |date= (help)CS1 maint: PMC format (link)
  9. ^ a b Coquerelle, Michael; Prados-Frutos, Juan Carlos; Rojo, Rosa; Mitteroecker, Philipp; Bastir, Markus (2013-11-15). Frayer, David (ed.). "Short Faces, Big Tongues: Developmental Origin of the Human Chin". PLoS ONE. 8 (11): e81287. doi:10.1371/journal.pone.0081287. ISSN 1932-6203. PMC 3829973. PMID 24260566.{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link)
  10. ^ a b Coquerelle, Michael; Prados-Frutos, Juan Carlos; Rojo, Rosa; Drake, Abby Grace; Murillo-Gonzalez, Jorge Alfonso; Mitteroecker, Philipp (2017-9). "The Fetal Origin of the Human Chin". Evolutionary Biology. 44 (3): 295–311. doi:10.1007/s11692-017-9408-9. ISSN 0071-3260. {{cite journal}}: Check date values in: |date= (help)
  11. ^ a b D. H, Enlow (1990). Facial growth. 3rd edition. Philadelphia: Saunders.
  12. ^ a b Holton, N. E.; Bonner, L. L.; Scott, J. E.; Marshall, S. D.; Franciscus, R. G.; Southard, T. E. (2015). "The ontogeny of the chin: an analysis of allometric and biomechanical scaling". Journal of Anatomy. 226 (6): 549–559. doi:10.1111/joa.12307. ISSN 1469-7580. PMC 4450959. PMID 25865897.{{cite journal}}: CS1 maint: PMC format (link)
  13. ^ University of Iowa. (2015, April 13). Why we have chins: Our chin comes from evolution, not mechanical forces. ScienceDaily. Retrieved July 28, 2018 from www.sciencedaily.com/releases/2015/04/150413183745.htm
  14. ^ Gauger Ann. (2016, February 11) On the origin of Chins. Evolution News. Retrieved July 28, 2018 from https://evolutionnews.org/2016/02/on_the_origin_o_8/
  15. ^ a b c d Mammalian Phenotype Browser: Cleft chin
  16. ^ Sharks of the world, Vol. 2, p. 143; by Leonard J. V. Compagno, Food and Agriculture Organization of the United Nations, 2001.
  17. ^ Rob Roy, p. 229 (in 1872 edition, pub. Osgood); by Sir Walter Scott, 1817.
  18. ^ [1]
  19. ^ Online Mendelian Inheritance in Man (OMIM): 119000
  20. ^ Starr, Barry. "Ask a Geneticist". Understanding Genetics. TheTech. Archived from the original on 2007-05-13. Retrieved 2007-07-01.
  21. ^ Günther, H. "Anomalien und Anomaliekomplexe in der Gegend des ersten Schlundbogens". Zeitschrift für menschliche Vererbungs- und Konstitutionslehre. 23: 43–52.; Lebow, M.R.; Sawin, P.B. "Inheritance of human facial features: a pedigree study involving length of face, prominent ears and chin cleft". Journal of Heredity. 32: 127–32. doi:10.1093/oxfordjournals.jhered.a105016.
  22. ^ چاه زنخدان the chin well Archived 2014-08-08 at the Wayback Machine
  23. ^ Larkin, Dimitrije E. Panfilov ; translated by Grahame (2005). Cosmetic surgery today. Stuttgart: Thieme Medical Publishers. p. 64. ISBN 1-58890-334-6.{{cite book}}: CS1 maint: multiple names: authors list (link)
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