Basic Science / Structures > Nails

Nails

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•cohesion between nailbed and undersurface of nail plate is so great that when the nail is avulsed, the separation does not occur at the junction between nail plate and nail bed, but rather between the nail bed and the subjacent dermis
•nail plate = protein with a high sulfur content
•fingernails grow approx. 1/3 the rate of hair (0.1mm/day)
•after avulsion: fingernails 6 months to grow out, toe nails 12 months

 

 

 

hmtoggle_plus1Hair vs. Nail:
•each has a matrix
•outer root sheath is comparable the nail bed
•inner root sheath is analogous to the cornified material supplied by the nail bed

 

 

Proximal portion of the matrix forms the superior aspect of the nail plate, and the distal matrix contributes to the inferior portion of the plate…

 

Pits:

•evidence of pinpoint damage to the matrix
•represent loci where tiny clusters of parakeratotic cells have been shed from the surface of the nail plate

 

White spots (leukonychia):

•result from damage to the distal matrix (vs. pits)
•represent parakeratotic cells in the deeper portion of the nail plate