Integumentary system — Nails

Anatomy & Physiology of Nails:  

Fingernails and toenails function to protect and support the ends or our digits.

Anatomy of nails (click on image for larger version):

03.05 fingers 013

03.05 fingers 013 labeled

03.05 fingers 013 drawing

03.05 fingers 013 drawing labeled

03.05 finger section drawing

03.05 finger section drawing labeled

 

Growth of nails (and why we don’t have claws):

Fingernails and toenails grow much in the same way that hair does.  In the nail matrix, which is at the proximal end of the nail just deep and a bit proximal to the lanula, there are keratinocyte stem cells dividing and giving rise to the cells that will become part of the nail.  The cells that are produced quickly fill with keratin (lots of keratin) and then die and become part of the nail.  So, nails are made of dead highly keratinized cells.  As the nail grows it moves toward the tip of the digit along the nail bed.  Cells are added to the nail along the length of the nail bed, they are simply added faster at the proximal end where the nail matrix is (that is why our nails grow out towards the end of our digits instead of up away from our digits the way the claws of cats, dogs, and other animals do… leading to claws).

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