What causes dimples?
A not-uncommon occurrence, when learning anatomy, is to learn something new about a particular part of the body and then wonder how that applies to what you observe on the bodies around you (e.g. your classmates, your family members). My students have been studying the neck and facial muscles for the past few weeks so it's probably not surprising that someone asked about dimples.
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Dimples, shown in the photo above, are a (usually) naturally-occurring indentation in the flesh on a part of the body. Folks are often most familiar with the facial variety. I have been fantastically unable to find information detailing the proportion of the population that has them, or I'd throw you that figure here.
According to the few peer-reviewed papers I was able to find in the medical literature (I was stoked that there were any), there is a correlation between dimples and an anatomical variation in particular facial muscles -- specifically, in the zygomaticus major muscles.
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| Gray's Anatomy |
On each side of the face, the zygomaticus major muscle originates at the zygomatic bone of the face and inserts, effectively, at the corner of the mouth. When it contracts, it pulls the corner of the mouth in a lateral and superior direction (as in a smile). Most humans have a single zygomaticus major muscle on each side of the face (as shown in the image above). Some studies of cadaveric tissue point to an anatomical correlation between having dimples and possessing a bifid (split in 2 parts) zygomaticus major muscle on each side of the face. This muscle has the same origin and action as the single zygomaticus major, but inserts at 2 points on each side (one above the corner of the mouth, one below the corner of the mouth). My guess (although I have not found it directly stated) is that the dimple would occur in the space between these 2 parts of the split zygomaticus major. Some studies suggest that folks with dimples also have connections between the hypodermis and dermis in this region (referred to as "dermal anchoring") which may contribute to the indentation. Dimple creation surgery seems to mimic such anchoring.
In short, the research points to a connection between dimples and an anatomical variation in one set of facial muscles, possibly accompanied by a variation in the attachment of skin to the underlying tissue.
References
Gassner, H.G., Rafii, A., Young, A., Murakami, C., Moe, K.S., Larrabee, W.F. (2008) Surgical anatomy of the face: implications for modern face-lift techniques. Arch Facial Plast Surg. 10(1): 9-19. doi: 10.1001/archfacial.2007.16.
Pessa, J.E., Zadoo, V.P., Garza, P.A., Adrian, E.K., Dewitt, A.I., Garza, J.R. (1998) Double or bifid zygomaticus major muscle: Anatomy, incidence, and clinical correlation. Clin Anat. 11(5):310-3. DOI: 10.1002/(SICI)1098-2353(1998)11:5<310::AID-CA3>3.0.CO;2-T
Cheek dimples are usually considered as an attractive feature of facial beauty. Unfortunately, not all beautiful girls have dimples. Literature on Dimple creation surgery is sparse.
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