I've always noticed I have lengthwise ridges on my fingernails. At one point they were so numerous I could almost play 'em like a washboard. The lines got really apparent if, say, I was playing in the dirt or got them stained with ground coffee of something.
Our son's doctor at a recent visit was staring intently at his hands and mentioning that she could often tell the condition of a person's digestive system by his/her nails, which kind of makes sense since nails are sort of the body's effluent.
I found this cool fingernail self-diagnosing chart, and about my ridges it says, "Aging, poor absorption of vitamins and minerals; thyroid disease; kidney failure." I might not be in imminent renal failure (although my trusty acupuncturist does have me on a kidney tonic...hm...) but the rest of the stuff is actually pretty accurate; in fact, as I've been trying to healthify myself in the last three months, and have definitely noticed that my ongles are less ridgey.
Again, I am not a medical professional nor am I suggesting any diagnosis of disease or recommending treatment, but I do suggest, check it out!
I have noticed that I have ridges and also brown arches on my finger nails. I have suffered 3 strokes, kidney disease, anemia and low thyroid, but I am curious about the brown arches across my finger nails.