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Earlobe

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Earlobe
Details
SystemAuditory system
Identifiers
Latinlobulus auriculae (singular), lobuli auricularum (plural)
TA98A15.3.01.003
TA2105
FMA60984
Anatomical terminology

The human earlobe (lobulus auriculae), the lower portion of the outer ear, is composed of tough areolar and adipose connective tissues, lacking the firmness and elasticity of the rest of the auricle (the external structure of the ear). In some cases the lower lobe is connected to the side of the face. Since the earlobe does not contain cartilage[1] it has a large blood supply and may help to warm the ears and maintain balance. However, earlobes are not generally considered to have any major biological function.[2] The earlobe contains many nerve endings, and for some people is an erogenous zone.

The zoologist Desmond Morris in his book The Naked Ape (1967) conjectured that the lobes developed as an additional erogenous zone to facilitate the extended sexuality necessary in the evolution of human monogamous pair bonding.[3]

A free earlobe
An attached earlobe

Organogenesis

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The earlobe, as a body part built of epithelium and connective tissue, might appear to be derived from dermatome.[4] But this is not the case, as in the surrounding tissue there are no somites and thus no dermatome. In this area, the dermis is derived from cells of mesenchymal cells: the mesenchyme is derived from the sclerotome and splanchnopleura located in the nearby regions of the torso.[5]

The earlobe as a body part arises and develops in the vicinity of auricular follicle, as a result of cascade induction:[6]

  1. The first-level inductor is the central segment of Archenteron's roof, which induces the production of the Medulla oblongata (part of the Hindbrain).
  2. The second-level inductor is the Medulla oblongata, which induces the production of a pair of auricular follicles derived from the mesoderm.
  3. The third-level inductor is the auricular follicle, which induces the production of the auditory bulla.

Genetics

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Clint Eastwood, who has an extreme form of attached ear lobe.

Earlobes average about 2 centimeters long, and elongate slightly with age.[7] Although the "free" vs. "attached" appearance of earlobes is often presented as an example of a simple "one gene – two alleles" Mendelian trait in humans, earlobes do not all fall neatly into either category; there is a continuous range from one extreme to the other, suggesting the influence of several genes.[8][9][10]

Recessive gene frequency in the selected worldwide populations
Population N Recessive gene frequency
(for attached ear lobes) 		Source
Africans ? 0.60 Messeri (1976)[11]
Afroamericans 242 0.56 Glass et al. (1952)[12]
Ainu ? 0.49 Messeri (1967)[11]
Babinga ? 0.87 Messeri (1967)[11]
Bavaria ? 0.84 Messeri (1967)[11]
Bosnia and Herzegovina 7,325 0.55 Hadžiselimović (1981)[13]
Brazil ? 0.34 Saldanha (1960)[14]
Cameroon ? 0.83 Messeri (1967)[11]
Canadian Aboriginals 532 0.68 Chaison (1963)[15]
China ? 0.62 Messeri (1967)[11]
Hong Kong 70 0.80 Lai, Walsh (1966)[16]
India: Bengal 100 0.49 Dutta (1963)[17]
Japan 70 0.82 Lai, Walsh (1966)[16]
Laponia ? 0.71 Messeri (1967)[11]
Micronesia ? 0.52 Messeri (1967)[11]
Nepal 169 0.66 Bhasin (1969)[18]
New Guinea 399 0.80 Lai, Walsh (1966)[16]
Nicobar 813 0.81 Gabel (1958)[19]
Papuans ? 0.54 Messeri (1967)[11]
Polynesia ? 0.39 Messeri (1967)[11]
Russia ? 0.59 Messeri (1967)[11]
Sardinia 403 0.53 Messeri (1967)[11]
Scotland 500 0.48 Chattopadhyay (1968)[20]
Somalia ? 0.42 Messeri (1967)[11]
Sweden 247 0.59 Wiener (1937)[21]
Tibet ? 0.68 Tiwari, Bhasin (1969)[22]
United States: Baltimore 380 0.63 Glass et al. (1952)[12]
United States: Brooklyn 248 0.92 Wiener (1937)[21]
United States: Buffalo 381 0.43 Dronamraju (1966)[23]
United States: Pennsylvania 241 0.50 Glass et al. (1952)[12]

Clinical issues

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Earlobes are normally smooth, but occasionally exhibit creases. Creased earlobes are sometimes associated with genetic disorders in children, including Beckwith-Wiedemann syndrome.[24] In some early studies, earlobe creases were thought to be associated with an increased risk of heart attack and coronary heart disease. But more recent studies have concluded that, since earlobes become more creased with age, and older people are more likely to have heart disease than younger people, age rather than intrinsic factors may account for the findings linking heart attack to earlobe creases.[24] The earlobe crease is also called Frank's Sign.

Society and culture

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Stretched earlobe piercing, Ethiopia

Earlobe piercing and stretching

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Piercing the earlobes is a commonplace activity in many cultures in many historical eras; no other location on the body is as commonly pierced. Consequently, injury to the earlobe due to the weight of heavy earrings is also common.[25] Some cultures practice earlobe stretching for decorative effects, using piercing ornaments to stretch and enlarge the earlobes to accommodate plugs.

Negative effects of wearing earrings

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Some research has found that the most frequent complications connected with wearing earrings are:[26]

A noticeable relationship has been found by Polish scientists between the piercing of young girls' earlobes and their subsequently developing allergic skin reactions.[27][28][29] In the view of Professor Ewa Czarnobilska, the manager of the research team, the primary reason for the allergies connected to earrings is the presence of nickel, which is a common component of the alloys used in jewelry production and leaches from the earrings.[28][29] The symptom seen is generally eczema, and is often misdiagnosed as a food allergy, for instance to milk. The specific mechanism in allergies caused by earrings is the contact of nickel ions with the lymphatic system.[28][29]

The study noted that children who stopped wearing earrings did not see the disappearance of the allergic symptoms. The immune system remembers the presence of the nickel ions in the person's blood and lymph, so the child can still react to:[28][29]

  • metal parts of wardrobe,
  • dental braces,
  • dental prosthesis,
  • orthotics,
  • meals cooked in pots with addition of nickel,
  • margarine (nickel is a catalyst in hydrogenation of unsaturated fats),
  • coins,
  • chocolate,
  • nuts,
  • leguminous vegetables,
  • wine, and
  • beer.

Research by allergists has found that in a sample of 428 pupils of ages 7–8 and 16–17 years old:[28][29]

  • 30% of the research population showed an allergy to nickel, and
  • the allergy occurred in girls who had started wearing earrings in early childhood.

References

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  1. ^ Steinberg, Avraham (2003). Encyclopedia of Jewish Medical Ethics: a Compilation of Jewish Medical Law on All Topics of Medical Interest. Jerusalem: Feldheim Publishers. p. 350. ISBN 1583305920.
  2. ^ Popelka (31 August 1999). "Re:Why do we have earlobes, what are they for, since when?". MadSci Network. Retrieved 16 July 2015.
  3. ^ Desmond Morris The Naked Ape: A Zoologist's Study of the Human Animal (Hardback: ISBN 0-07-043174-4; Reprint: ISBN 0-385-33430-3) Jonathan Cape, 1967 . Chapter 2, page 59 of Corgi paperback ed
  4. ^ Jura, Krzanowska & Rzehak 1983, p. 355, 357.
  5. ^ Jura, Krzanowska & Rzehak 1983, p. 358.
  6. ^ Jura, Krzanowska & Rzehak 1983, p. 395.
  7. ^ Azaria R, Adler N, Silfen R, Regev D, Hauben DJ (June 2003). "Morphometry of the adult human earlobe: a study of 547 subjects and clinical application". Plast. Reconstr. Surg. 111 (7): 2398–2402, discussion 2403–2404. doi:10.1097/01.PRS.0000060995.99380.DE. PMID 12794488. S2CID 38636234.
  8. ^ Mader S. S. (2000): Human Biology. McGraw–Hill, New York, ISBN 0-07-290584-0.
  9. ^ Boaz N. T. (1999): Essentials of biological anthropology. Prentice Hall, New Jersey,ISBN 0-13-080793-1.
  10. ^ Dutta, P; Ganguly, P (1965). "Further Observations on Ear Lobe Attachment". Acta Genet Stat Med. 15: 77–86. doi:10.1159/000151894. PMID 14277139.
  11. ^ a b c d e f g h i j k l m Messeri E. (1967): "Variabilità morfologica del lobolo auricolare in Sardegna". Atti Soc. Peloritana, Sc. Fis. mat. nat., 13 (1/2): 89.
  12. ^ a b c Glass B., Sacks M. S., John E. F., Hess C. (1952): "Genetic Drift in a Religious Isolate: An Analysis of the Causes of Variation in Blood Group and Other Gene Frequencies in a Small Population". Phys. Anthrop., 144.
  13. ^ Hadžiselimović R. (1981): "Genetic distance among local human populations in Bosnia and Herzegovina (Yugoslavia)". Coll. Antrop., 5. (Suppl.): 63–66.
  14. ^ Saldanha, P. H. (1960). "Frequencies of consanguineous marriages in North-east of São Paulo, Brazil". Acta Genet. 10 (1): 71–88. doi:10.1159/000151120. PMID 13745577.
  15. ^ Chaisson, L. P. (1963). "Gene frequencies in the Micmac Indians". J. Hered. 54 (2): 229–36. doi:10.1093/oxfordjournals.jhered.a107255. PMID 14086177.
  16. ^ a b c Lai, Y. C.; Walsh, R. J. (1966). "Observation on ear lobe types". Acta Genet. Statist. Med. 16 (3): 250–7. doi:10.1159/000151971. PMID 5953713.
  17. ^ Dutta, P. C. (1963). "A note on the ear lobe". Acta Genet. Statist. Med. 15 (3): 290–4. doi:10.1159/000151809. PMID 14101393.
  18. ^ Bhasin, M. K. (1969). "Ear lobe attachment among Newars of Nepal". Hum. Hered. 19 (5): 506–8. doi:10.1159/000152259. PMID 5365889.
  19. ^ Gabel, N. E. (1958). "A racial study of the Fijans". Anthrop. Rec. 20 (1): 22.
  20. ^ Chatopadhyay, P. K. (1968). "A note on the ear lobe attachment among the Jats and Ahirs". Acta Genet. Statist. Med. 18 (3): 277–82. doi:10.1159/000152145. PMID 5694908.
  21. ^ a b Wiener (1937). "Complications in ear genetics". J. Hered. 28 (3): 425. doi:10.1093/oxfordjournals.jhered.a104304.
  22. ^ Tiwari, S. C.; Bhasin, M. K. (1969). "Frequency of hand clasping and ear lobe attachment in Tibetians". J. Hered. 19 (4): 658–661. doi:10.1159/000152280. PMID 5399262.
  23. ^ Dronamraju, K. R. (1966). "Ear lobe attachment in the Buffalo region". Acta Genet. Statist. Med. 16 (3): 258–64. doi:10.1159/000151972. PMID 5953714.
  24. ^ a b MedlinePlus Encyclopedia: Earlobe creases
  25. ^ HELGAADMIN (15 December 2014). "Are your Earlobes Attached?". Quantum Healing Institute Blog.
  26. ^ Watson, D (2002). "Torn earlobe repair". Otolaryngologic Clinics of North America. 35 (1): 187–205, vii–viii. doi:10.1016/s0030-6665(03)00102-6. PMID 11781215.
  27. ^ Harmful earrings (pl. Szkodliwe kolczyki), Fizjointormator. Retrieved 2015-04-01
  28. ^ a b c d e Polish Scientists learn: earrings harm children (pl. Polscy naukowcy ostrzegają: kolczyki szkodzą dzieciom) Tvn24. Retrieved 2015-04-01
  29. ^ a b c d e Czarnobilska E.; Oblutowicz K.; Dyga W.; Wsołek-Wnek K.; Śpiewak R. (May 2009). "Contact hypersensitivity and allergic contact dermatitis among school children and teenagers with eczema". Contact Dermatitis. 60 (5). John Wiley & Sons A/S: 264–269. doi:10.1111/j.1600-0536.2009.01537.x. PMID 19397618. S2CID 30920753.

Further reading

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