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| Earlobe | |
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| Latin | lobulus auriculae (singular), lobuli auricularum (plural) |
| Gray's | subject #229 1034 |
| System | Auditory system |
On the ear of humans and many other animals, the earlobe('lobulus auriculæ'), sometimes simply lobe or lobule) is the soft lower part of the external ear, similar in composition to the labia, or pinna. It is the lowermost portion of the human pinna, projecting below the antitragus. The earlobe is composed of tough areolar and adipose (fatty) connective tissues, lacking the firmness and elasticity of the rest of the pinna. Since the earlobe does not contain cartilage the earlobe has a large blood supply and may help to warm the ears and maintain balance but generally earlobes are not considered to have any major biological function.[1]
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Size and shape
Earlobes average about 2 cm long, and elongate slightly with age.[2] Human earlobes may be free or detached (hanging free from the head) or attached (joined to the head). Whether the earlobe is free or attached is a classic example of a simple genetic dominance relationship; freely hanging earlobes are the dominant allele and attached earlobes are recessive. Therefore, a person whose genes contain one allele for free earlobes and one for attached lobes will display the freely hanging lobe trait. It is a common misconception that this implies a precise 3-to-1 ratio between free and attached lobes in the human population. Such a ratio would require that the allele frequency for free lobes were precisely 50%, which there is no reason to assume. One study [3] found that the frequency of attached earlobes among Japanese subjects was 67.1%, and in Chinese subjects it was 64.3%.
Earlobes are normally smooth, but occasionally exhibit creases. Creased earlobes are associated with genetic disorders, including Beckwith-Wiedemann syndrome. Earlobe creases are also associated with an increased risk of heart attack and coronary heart disease; however, since earlobes become more creased with age, and older people are more likely to experience heart disease than younger people, age may account for the findings linking heart attack to earlobe creases.[4]
The earlobe contains many nerve endings, and for some people is an erogenous zone.
Earlobe piercing
Around the world and throughout human history, the earlobe is the most common location for a body piercing. Tearing of the earlobe from the weight of very heavy earrings, or traumatic pull of an earring, is fairly common. The repair of such a tear is usually not difficultcitation needed. Some cultures practice earlobe stretching, using piercing ornaments to stretch and enlarge the earlobes. Piercing the earlobe poses a much lower risk of infection than piercing other parts of the earcitation needed. After that time, earrings can be changed, but if the hole is left unfilled for an extended period of time, there is a chance of the piercing closing. After healing, earlobe piercings will shrink to smaller gauges in the prolonged absence of earrings, but may never completely disappear.
See also
References
- ^ Popelka, Gerald, ""Re:Why do we have earlobes, what are they for, since when?" MadSci Network, posted Aug 31 1999. [1]
- ^ Azaria, R., et al. Morphometry of the Adult Earlobe: A Study of 547 Subjects and Clinical Application (abstract), American Society of Plastic Surgeons, 2003. [2].
- ^ LY Lai, RJ Walsh, "Observations on ear lobe types." Acta Genet Stat Med, 1966
- ^ U.S. National Library of Medicine and National Institute of Health, "Earlobe Creases." Medical Encyclopedia, [3]. Updated 10/20/2004.
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Wikipedia content modification information:
- This page was last modified on 10 October 2008, at 04:01.
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