RT Book, Section
A1 T. Desman, Garrett
A1 Barnhill, Raymond L.
A2 Barnhill, Raymond L.
A2 Crowson, A. Neil
A2 Magro, Cynthia M.
A2 Piepkorn, Michael W.
A2 Kutzner, Heinz
A2 Desman, Garrett T.
SR Print(0)
ID 1178393302
T1 Alterations of Collagen and Elastin
T2 Barnhill's Dermatopathology, 4e
YR 2020
FD 2020
PB McGraw Hill Education
PP New York, NY
SN 9780071828222
LK dermatology.mhmedical.com/content.aspx?aid=1178393302
RD 2024/04/19
AB The  major  function  of  the  skin  is  to  serve  as  a  barrier  to  various  exogenous  substances,  chemicals,  and  microbes.  Collagen,  ground  substance  (dermal  mucin),  and  elastic  fibers  are  the  3  major  components  of  the  dermis  and  are  crucial  to  maintaining  the  integrity  and  elasticity  of  the  skin.  Collagen  is  the  most  abundant  of  the  3  components  of  the  dermis  (80%  by  dry  weight),  consisting  primarily  of  type  I  collagen  in  the  reticular  dermis,  type  III  collagen  in  the  papillary  and  adventitial  dermis,  and  type  IV  collagen  forming  basement  membranes  for  epithelial  structures  and  blood  vessels.  Over  20  distinct  collagens  are  now  recognized.1,2  The  amino  acid  sequence  and  composition  determines  the  individual  collagen  type.  Collagens  are  composed  of  3  polypeptides,  or  alpha  chains,  that  assume  a  stabilizing  triple-helical  conformation  depending  on  glycine  residues  located  at  every  third  position  of  the  polypeptides.  Hydroxyproline  (synthesized  from  proline)  is  necessary  for  triple-helix  stability  at  physiologic  temperatures.  Fibroblasts  initially  secrete  collagen  in  a  soluble  form  (procollagen),  which  is  then  cleaved  to  insoluble  fibers  (collagen)  that  are  crosslinked  by  oxidation  of  lysyl  and  hydroxylysine  residues.  It  is  this  crosslinking  that  gives  collagen  its  tensile  strength.  Whereas  type  I  collagen  provides  tensile  strength  to  the  skin,  type  III  collagen  participates  in  anchoring  the  epidermis  and  adnexae  to  the  dermis.