Dimples are natural indentations that can appear on various parts of the human body. These subtle depressions in the skin are often present from birth and are generally considered harmless. While some dimples are visible all the time, others become noticeable only with certain facial expressions or body movements. Their presence is typically linked to variations in underlying muscle or connective tissue structures.
Dimples on the Face
Facial dimples are perhaps the most recognized type of dimple, often associated with smiles. Cheek dimples are the most common, appearing as small depressions on the sides of the mouth. They can be bilateral (on both cheeks) or unilateral (on one side). Bilateral cheek dimples are more common than unilateral ones. The appearance of cheek dimples can vary, with some being vertical (longitudinal) and others horizontal (transverse), depending on the underlying muscle structure.
Another distinct facial dimple is the chin dimple, also called a cleft chin. This indentation appears in the center of the chin. Unlike cheek dimples, which often appear with movement, a chin dimple remains visible without specific facial expressions. While cheek dimples are more frequently observed in females, chin dimples tend to be more common in males.
Dimples on the Body
Dimples can also appear on other areas of the body. A common example is the pair of indentations on the lower back, often referred to as “dimples of Venus.” Scientifically known as fossae lumbales laterales, these symmetrical depressions are located just above the buttocks.
They are situated directly over the sacroiliac joints, where the sacrum connects to the ilium of the pelvis. These dimples are formed by a short ligament that connects the skin to the posterior superior iliac spine, a part of the hip bone. The term “dimples of Apollo” is sometimes used to describe these indentations in men.
Another type of dimple on the lower back is a sacral dimple, also known as a pilonidal dimple or spinal dimple. This is a small indentation or pit, typically located just above the crease between the buttocks. Most sacral dimples are small, shallow, and harmless. However, some sacral dimples can be larger, deeper, or located off the midline, and may warrant medical evaluation to ensure they are not associated with underlying spinal conditions.
How Dimples Form
The formation of dimples is primarily due to variations in muscle structure and connective tissue. For cheek dimples, the explanation involves the zygomaticus major muscle. This muscle is responsible for raising the corners of the mouth when a person smiles.
In individuals with dimples, the zygomaticus major muscle often divides into two separate bundles, a variation known as a bifid zygomaticus major muscle. One bundle attaches to the corner of the mouth, while the other attaches below the corner of the mouth and is tethered to the overlying skin. When this muscle contracts during a smile, the skin is pulled inward, creating the characteristic indentation.
Chin dimples form differently and are not related to muscle variations. They are typically caused by an incomplete fusion of the two halves of the lower jawbone during fetal development. This results in a small gap or notch in the bone, which the overlying skin follows, creating the indentation. While dimples often appear to run in families, suggesting a genetic component, the exact inheritance patterns are complex and not fully understood. However, the inheritance is considered irregular dominant, meaning multiple genes may be involved, making their appearance somewhat unpredictable.