| Earlobe | |
|---|---|
 | |
| Details | |
| System | Auditory system |
| Identifiers | |
| Latin | lobulus auriculae (singular), lobuli auricularum (plural) |
| TA98 | A15.3.01.003 |
| TA2 | 105 |
| FMA | 60984 |
| Anatomical terminology | |
Thehuman earlobe (lobulus auriculae), the lower portion of theouter ear, is composed of toughareolar andadiposeconnective tissues, lacking the firmness and elasticity of the rest of theauricle (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 containcartilage[1] it has a largeblood supply and may help to warm the ears. However, earlobes are not generally considered to have any major biological function.[2] The earlobe contains manynerve endings, and for some people is anerogenous zone.
The zoologistDesmond Morris in his bookThe 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]
The earlobe, as a body part built ofepithelium andconnective tissue, might appear to be derived fromdermatome.[4] But this is not the case, as in the surrounding tissue there are nosomites and thus no dermatome. In this area, thedermis is derived from cells ofmesenchymal cells: the mesenchyme is derived from thesclerotome and splanchnopleura located in the nearby regions of thetorso.[5]
The earlobe as a body part arises and develops in the vicinity of auricular follicle, as a result of cascade induction:[6]
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]
| 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] |
Earlobes are normally smooth, but occasionally exhibit creases. Creased earlobes are sometimes associated with genetic disorders in children, includingBeckwith-Wiedemann syndrome.[24] In some early studies, earlobe creases were thought to be associated with an increased risk ofheart attack andcoronary 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 calledFrank's Sign.
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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 practiceearlobe stretching for decorative effects, using piercing ornaments to stretch and enlarge the earlobes to accommodateplugs.
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 ofnickel, which is a common component of the alloys used in jewelry production and leaches from the earrings.[28][29] The symptom seen is generallyeczema, and is often misdiagnosed as afood allergy, for instance to milk. The specific mechanism in allergies caused by earrings is the contact of nickel ions with thelymphatic system.[28][29]
The study noted that children who stopped wearing earrings did not see the disappearance of the allergic symptoms. Theimmune system remembers the presence of the nickel ions in the person'sblood andlymph, so the child can still react to:[28][29]
Research by allergists has found that in a sample of 428 pupils of ages 7–8 and 16–17 years old:[28][29]
