Finger nails
photo: B. Velakanni Raj
Why do we have a small white area at the base of our finger nails?
SUMATH SHANKAR
Hyderabad
The small white area at the base of nail is called lunule. The nail grows at the rate of 0.05mm per day. The whole nail is made of hardcore keratin, and it is hard because it serves the dual purpose of protection to the tip of the finger, as well as enhancing the touch sensation at the tip of the finger.
In the tip, different points of touch nearing 1 mm can be appreciated, wherein in the body it requires 5 cms to different two point of touch, and this enhancement of sensitiveness is due to the hard keratin, which is tight, hard protein materials, as in hair.
The nail grows from the area of nail bed, which is the base portion of the nail. The base portion of the nail is packed with hard keratin, which moves towards the tip of the finger as the nail grows.
As the base is thick with keratin, the underlining blood vessels are not visible, whereas the rest of nail is exposed to blood filled capillaries underneath.
As the nail is transparent it is visible as a red or rose area, in contrast to the base, which is white in colour. The crescent descends down in smaller arches from thumb to the little finger, in size.
The crescent nature of the lunule is due to the fact that it is packed with keratin tightly, and the axial portion of the nail grows more in velocity than peripheral parts, and hence the centre portion is pulled forwards to create an arch.
The lunule is covered with a fold of skin called cuticle, which actually protects the base of nail from injury. The small dots white and some times brown, are defective keratinized areas, which are pushed forward.
DR. V. NAGARAJAN
PROFESSOR EMERITUS IN NEURO-SCIENCES, TAMIL NADU DR. MGR MEDICAL UNIVERSITY MADU
nag9999@gmail.com
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