Skin fold

Many skin folds are distinct, heritable anatomical features, and may be used for identification of animal species, while others are non-specific and may be produced either by individual development of an organism or by arbitrary application of force to skin, either by the actions of the muscles of the body or by external force, e.g., gravity.

Skin folds are of interest for cosmetology, as some kinds may be considered aesthetically undesirable, and for medicine, because some of them are susceptible to inflammation and infection.

The skin crease as a fixed and permanent line, according to their histology, is related to connective tissue attachments with the underlying structures or extensions of the underlying muscle fibers in the dermis of the crease site.

It is essential to use appropriate terms that accurately reflect the anatomic structure and histology when referring to the skin lines.

[1][2] The following distinct skin fold types are among the roughly 100[3] identified in human anatomy:

Phalangeal creases of the finger (with an extra crease in the second finger).
In projectional radiography , skin folds may mimic fractures: In this case a hip fracture (black arrow) next to a skin fold (white arrow).