▁the ▁skin ▁is ▁the ▁second ▁largest ▁organ ▁in ▁the ▁human ▁body ▁( the ▁inside ▁of ▁the ▁small ▁int est ine ▁is ▁ 1 5 ▁to ▁ 2 0 ▁times ▁larger ). ▁For ▁the ▁average ▁adult ▁human , ▁the ▁skin ▁has ▁a ▁surface ▁area ▁of ▁between ▁ 1 . 5 - 2 . 0 ▁square ▁metres ▁( 1 6 . 1 - 2 1 . 5 ▁sq ▁ft .). ▁The ▁thick ness ▁of ▁the ▁skin ▁var ies ▁consider ably ▁over ▁all ▁parts ▁of ▁the ▁body , ▁and ▁between ▁men ▁and ▁women ▁and ▁the ▁young ▁and ▁the ▁old . ▁An ▁example ▁is ▁the ▁skin ▁on ▁the ▁for ear m ▁which ▁is ▁on ▁average ▁ 1 . 3   mm ▁in ▁the ▁male ▁and ▁ 1 . 2 6   mm ▁in ▁the ▁female . ▁The ▁average ▁square ▁in ch ▁( 6 . 5   cm ² ) ▁of ▁skin ▁holds ▁ 6 5 0 ▁swe at ▁g lands , ▁ 2 0 ▁blood ▁vessels , ▁ 6 0 , 0 0 0 ▁mel an ocy tes , ▁and ▁more ▁than ▁ 1 , 0 0 0 ▁n erve ▁end ings . ▁The ▁average ▁human ▁skin ▁cell ▁is ▁about ▁ 3 0 ▁mic rom et res ▁in ▁diameter , ▁but ▁there ▁are ▁variants . ▁A ▁skin ▁cell ▁usually ▁ranges ▁from ▁ 2 5 - 4 0 ▁mic rom et res ▁( squ ared ), ▁depending ▁on ▁a ▁variety ▁of ▁factors . ▁ ▁Sk in ▁is ▁composed ▁of ▁three ▁primary ▁layers : ▁the ▁e pid erm is