Earlobe#Inheritance

{{short description|Part of the ear}}

{{Use dmy dates|date=January 2024}}

{{Infobox anatomy

| Name = Earlobe

| Latin = lobulus auriculae (singular), lobuli auricularum (plural)

| Image = Gray904.png

| Width = 120

| Caption =

| Image2 =

| Caption2 =

| System = Auditory system

| Precursor =

}}

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 cartilageSteinberg, Avraham (2003). [https://books.google.com/books?id=aaklGZAID08C&pg=PA350&lpg=PA350&dq=false Encyclopedia of Jewish Medical Ethics: a Compilation of Jewish Medical Law on All Topics of Medical Interest]. Jerusalem: Feldheim Publishers. p. 350. {{ISBN|1583305920}}. it has a large blood supply and may help to warm the ears. However, earlobes are not generally considered to have any major biological function.{{cite web |author=Popelka |title=Re:Why do we have earlobes, what are they for, since when? |date=31 August 1999 |publisher=MadSci Network |url=http://www.madsci.org/posts/archives/aug99/934627537.Ev.r.html |access-date=16 July 2015}} 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.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

{{multiple image

| align = right

| image1 = Lharina耳朵.jpg

| width1 = 130

| alt1 =

| caption1 = A free earlobe

| image2 = TattooedAttachedEarlobe.png

| width2 = 110

| alt2 =

| caption2 = An attached earlobe

| footer =

}}

Organogenesis

The earlobe, as a body part built of epithelium and connective tissue, might appear to be derived from dermatome.{{sfn|Jura|Krzanowska|Rzehak|1983|p=355, 357}} 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.{{sfn|Jura|Krzanowska|Rzehak|1983|p=358}}

The earlobe as a body part arises and develops in the vicinity of auricular follicle, as a result of cascade induction:{{sfn|Jura|Krzanowska|Rzehak|1983|p=395}}

  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

File:ClintEastwoodSept10TIFF.jpg, who has an extreme form of attached ear lobe.]]

Earlobes average about 2 centimeters long, and elongate slightly with age.{{cite journal |vauthors=Azaria R, Adler N, Silfen R, Regev D, Hauben DJ |title=Morphometry of the adult human earlobe: a study of 547 subjects and clinical application |journal=Plast. Reconstr. Surg. |volume=111 |issue=7 |pages=2398–2402; discussion 2403–2404 |date=June 2003 |pmid=12794488 |doi=10.1097/01.PRS.0000060995.99380.DE |s2cid=38636234 }} 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.Mader S. S. (2000): Human Biology. McGraw–Hill, New York, {{ISBN|0-07-290584-0}}.Boaz N. T. (1999): Essentials of biological anthropology. Prentice Hall, New Jersey,{{ISBN|0-13-080793-1}}.{{cite journal | pmid = 14277139 | volume=15 | year=1965 | journal=Acta Genet Stat Med | pages=77–86 | last1 = Dutta | first1 = P | last2 = Ganguly | first2 = P | title=Further Observations on Ear Lobe Attachment | doi=10.1159/000151894}}

class="wikitable sortable"

|+ Recessive gene frequency in the selected worldwide populations

Population

! N

!Recessive gene frequency
(for attached ear lobes)

!Source

Africans

|style="text-align:right"|?

|style="text-align:right"|0.60

|Messeri (1976)Messeri E. (1967): "Variabilità morfologica del lobolo auricolare in Sardegna". Atti Soc. Peloritana, Sc. Fis. mat. nat., 13 (1/2): 89.

Afroamericans

|style="text-align:right"|242

|style="text-align:right"|0.56

|Glass et al. (1952)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.

Ainu

|style="text-align:right"|?

|style="text-align:right"|0.49

|Messeri (1967)

Babinga

|style="text-align:right"|?

|style="text-align:right"|0.87

| Messeri (1967)

Bavaria

|style="text-align:right"|?

|style="text-align:right"|0.84

| Messeri (1967)

Bosnia and Herzegovina

|style="text-align:right"|7,325

|style="text-align:right"|0.55

|Hadžiselimović (1981)Hadžiselimović R. (1981): "Genetic distance among local human populations in Bosnia and Herzegovina (Yugoslavia)". Coll. Antrop., 5. (Suppl.): 63–66.

Brazil

|style="text-align:right"|?

|style="text-align:right"|0.34

| Saldanha (1960){{cite journal | last1 = Saldanha | first1 = P. H. | year = 1960 | title = Frequencies of consanguineous marriages in North-east of São Paulo, Brazil | journal = Acta Genet | volume = 10 | issue = 1| pages = 71–88 | doi = 10.1159/000151120 | pmid = 13745577 }}

Cameroon

|style="text-align:right"|?

|style="text-align:right"|0.83

| Messeri (1967)

Canadian Aboriginals

|style="text-align:right"|532

|style="text-align:right"|0.68

| Chaison (1963){{cite journal | last1 = Chaisson | first1 = L. P. | year = 1963 | title = Gene frequencies in the Micmac Indians | journal = J. Hered. | volume = 54 | issue = 2| pages = 229–36 | doi = 10.1093/oxfordjournals.jhered.a107255 | pmid = 14086177 }}

China

|style="text-align:right"|?

|style="text-align:right"|0.62

| Messeri (1967)

Hong Kong

|style="text-align:right"|70

|style="text-align:right"|0.80

| Lai, Walsh (1966){{cite journal | last1 = Lai | first1 = Y. C. | last2 = Walsh | first2 = R. J. | year = 1966 | title = Observation on ear lobe types | journal = Acta Genet. Statist. Med. | volume = 16 | issue = 3| pages = 250–7 | doi = 10.1159/000151971 | pmid = 5953713 }}

India: Bengal

|style="text-align:right"|100

|style="text-align:right"|0.49

| Dutta (1963){{cite journal | last1 = Dutta | first1 = P. C. | year = 1963 | title = A note on the ear lobe | journal = Acta Genet. Statist. Med. | volume = 15 | issue = 3| pages = 290–4 | doi = 10.1159/000151809 | pmid = 14101393 }}

Japan

|style="text-align:right"|70

|style="text-align:right"|0.82

| Lai, Walsh (1966)

Lapland

|style="text-align:right"|?

|style="text-align:right"|0.71

| Messeri (1967)

Micronesia

|style="text-align:right"|?

|style="text-align:right"|0.52

| Messeri (1967)

Nepal

|style="text-align:right"|169

|style="text-align:right"|0.66

|Bhasin (1969){{cite journal | last1 = Bhasin | first1 = M. K. | year = 1969 | title = Ear lobe attachment among Newars of Nepal | journal = Hum. Hered. | volume = 19 | issue = 5| pages = 506–8 | doi = 10.1159/000152259 | pmid = 5365889 }}

New Guinea

|style="text-align:right"|399

|style="text-align:right"|0.80

| Lai, Walsh (1966)

Nicobar

|style="text-align:right"|813

|style="text-align:right"|0.81

|Gabel (1958){{cite journal | last1 = Gabel | first1 = N. E. | year = 1958 | title = A racial study of the Fijans | journal = Anthrop. Rec. | volume = 20 | issue = 1| page = 22 }}

Papuans

|style="text-align:right"|?

|style="text-align:right"|0.54

| Messeri (1967)

Polynesia

|style="text-align:right"| ?

|style="text-align:right"|0.39

| Messeri (1967)

Russia

|style="text-align:right"|?

|style="text-align:right"|0.59

| Messeri (1967)

Sardinia

|style="text-align:right"|403

|style="text-align:right"|0.53

| Messeri (1967)

Scotland

|style="text-align:right"|500

|style="text-align:right"|0.48

|Chattopadhyay (1968){{cite journal | last1 = Chatopadhyay | first1 = P. K. | year = 1968 | title = A note on the ear lobe attachment among the Jats and Ahirs | journal = Acta Genet. Statist. Med. | volume = 18 | issue = 3| pages = 277–82 | doi = 10.1159/000152145 | pmid = 5694908 }}

Somalia

|style="text-align:right"|?

|style="text-align:right"|0.42

| Messeri (1967)

Sweden

|style="text-align:right"|247

|style="text-align:right"|0.59

| Wiener (1937){{cite journal | last1 = Wiener | year = 1937 | title = Complications in ear genetics | journal = J. Hered. | volume = 28 | issue = 3| page = 425 | doi = 10.1093/oxfordjournals.jhered.a104304}}

Tibet

|style="text-align:right"|?

|style="text-align:right"|0.68

| Tiwari, Bhasin (1969){{cite journal | last1 = Tiwari | first1 = S. C. | last2 = Bhasin | first2 = M. K. | year = 1969 | title = Frequency of hand clasping and ear lobe attachment in Tibetians | journal = J. Hered. | volume = 19 | issue = 4| pages = 658–661 | doi = 10.1159/000152280 | pmid = 5399262 }}

United States: Baltimore

|style="text-align:right"|380

|style="text-align:right"|0.63

| Glass et al. (1952)

United States: Brooklyn

|style="text-align:right"|248

|style="text-align:right"|0.92

| Wiener (1937)

United States: Buffalo

|style="text-align:right"|381

|style="text-align:right"|0.43

| Dronamraju (1966){{cite journal | last1 = Dronamraju | first1 = K. R. | year = 1966 | title = Ear lobe attachment in the Buffalo region | journal = Acta Genet. Statist. Med. | volume = 16 | issue = 3| pages = 258–64 | doi = 10.1159/000151972 | pmid = 5953714 }}

United States: Pennsylvania

|style="text-align:right"|241

|style="text-align:right"|0.50

| Glass et al. (1952)

Clinical issues

Earlobes are normally smooth, but occasionally exhibit creases. Creased earlobes are sometimes associated with genetic disorders in children, including Beckwith-Wiedemann syndrome. 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.{{MedlinePlusEncyclopedia|003045|Earlobe creases}} The earlobe crease is also called Frank's Sign.

Society and culture

= Earlobe piercing and stretching=

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.{{cite web |author=HELGAADMIN |title=Are your Earlobes Attached? |date=15 December 2014 |publisher=Quantum Healing Institute Blog |url=http://www.quantumhealinginstituteblog.com/2014/info/are-your-earlobes-attached/}} 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=

Some research has found that the most frequent complications connected with wearing earrings are:{{cite journal |last1=Watson |first1=D |title=Torn earlobe repair |journal=Otolaryngologic Clinics of North America |volume=35 |issue=1 |pages=187–205, vii–viii |year=2002 |pmid=11781215 |doi=10.1016/s0030-6665(03)00102-6}}

A noticeable relationship has been found by Polish scientists between the piercing of young girls' earlobes and their subsequently developing allergic skin reactions.[http://www.fizjoinformator.pl/szkodliwe-kolczyki/ Harmful earrings (pl. Szkodliwe kolczyki)], Fizjointormator. Retrieved 2015-04-01[http://www.tvn24.pl/krakow,50/polscy-naukowcy-ostrzegaja-kolczyki-szkodza-dzieciom,462077.html Polish Scientists learn: earrings harm children (pl. Polscy naukowcy ostrzegają: kolczyki szkodzą dzieciom)] Tvn24. Retrieved 2015-04-01{{cite journal |author1=Czarnobilska E. |author2=Oblutowicz K. |author3=Dyga W. |author4=Wsołek-Wnek K. |author5=Śpiewak R. |title=Contact hypersensitivity and allergic contact dermatitis among school children and teenagers with eczema. |journal=Contact Dermatitis |volume=60 |issue=5 |pages=264–269 |date=May 2009 |publisher= John Wiley & Sons A/S |doi=10.1111/j.1600-0536.2009.01537.x|pmid=19397618 |s2cid=30920753 |doi-access=free }} 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. 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.

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:

  • 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:

  • 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

{{Reflist}}

Further reading

  • {{cite book |last1=Jura |first1=Czesław |last2= Krzanowska |first2= Halina |last3= Rzehak |first3= Karol |year=1983 |title=Podstawy embriologii zwierząt |trans-title=Bases of Animals' Embryology |edition=1st |location=Warsaw |publisher=Wydawnictwo Naukowe PWN (En.: Polish Scientific Publishers PWN) |isbn=83-01-04241-9}}

{{Auditory system}}

{{Authority control}}

Category:Ear

de:Ohrmuschel#Ohrläppchen