Re: Why do some people's fingernails have grooves?

REFERENCE(S) IF NOT READILY AVAILABLE:
1)Morris' Human Anatomy, B.J.Anson,editor, 12th edition, Blakiston
Division of McGraw-Hill Company
2)A Textbook of Histology, W.Bloom and D.W.Fawcett, 10th Edition,
W.B.Saunders Company

If you look at a human fingernail with a low power hand lens, using the surface of the nail for reference and strong low-angled lighting, you will see that these "grooves" are really tiny parallel RIDGES elevated slightly from the nail's surface; rather than "depressed valleys," which is the way that I interpret the word groove.

Both references listed above describe the nail bed, which is the specialized skin surface underneath the nail, as possessing a ridged surface (the technical gross anatomical term for these ridges is: THE CRISTAE MATRICIS UNGUIS) with the ridges arranged in a parallel manner and directed longitudinally or along the long axis of the finger. This appearance is homologous (similar in structure or origin) to the DERMAL PAPILLAE of normal human skin. Rather than having the typical appearance of tiny volcanoes, the dermal papillae under the nail take the form of long parallel "mountain ridges" directed towards the finger tips. Since this ridged nail bed, with its basal germinative cell layer, is responsible for the formation and continual growth of the nail, it conveys this parallel ridged structure to the generated nail itself!! Fantastic don't you think?

The nail can sometimes give clues to certain systemic illnesses, such as 1)hypochromic anemia (with pale spoon-shaped nails when very severe)and 2)thromboemboli (minute blood clots) from the heart (splinter hemorrahges in the nails), but these conditions are not common.

If you still have reference to definite grooves or longitudinal depressions in some human nails, then please redirect your question to a skin specialist (dermatologist), since nails are just specialized parts of your skin.

Thank you for this interesting chance to review my anatomy and good luck in your life-long learning through observation.

Sincerely,
Scott