Earlobe
From Wikipedia, the free encyclopedia
| Earlobe | |
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| Latin | lobulus auriculae (singular), lobuli auricularum (plural) |
| Gray's | subject #229 1034 |
| System | Auditory system |
The earlobe is, in humans and many other animals, the soft lower part of the external ear. 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]
[edit] 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. The frequency of attached earlobes among Japanese subjects is 67.1%, and in Chinese it is 64.3%.[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] See Frank's Sign.
The earlobe contains many nerve endings, and for some people is an erogenous zone.
[edit] Earlobe piercing
Around the world and throughout human history, the earlobe is the most common location for a body piercing. It is common to tear the earlobe with the weight of very heavy earring, or a traumatic pull of an earring. Some cultures practice earlobe stretching, using piercing ornaments to stretch and enlarge the earlobes.
[edit] 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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