The  Integumentary  system  consists  of  

your  skin  and  accessory  structures  such  

as  hair  and  sweat  glands.  Your  skin  is  

the  largest  organ  of  your  body,  and  

performs  a  variety  of  functions.  The  

skin  is  a  major  source  of  protection,  as  

it  does  cover  your  entire  body.  Sweat  

glands  allow  the  thermoregulation  of  

your  body  by  secreting  when  you  are  

hot.  Melanocytes  produce  pigment,  

which  

protects  

against  UV  

rays.  Hair  

provides  

protection,  mainly  on  your  head,  as  

well  as  insulation  for  your  bodily  heat.  

Each  hair  is  also  connected  to  an  

arrector  pili  muscle  that  causes  the  

phenomena  known  as  “goosebumps”  

when  we  become  cold,  scared,  or  

excited.  

       References  for  photos:    

• http://www.drsecretstore.com/blog/  

• http://www.unexpectedpages.com/files/humanbody/goose-­‐bumps/goose-­‐bumps.php  

• http://www.health.com/health/gallery/0,,20399770,00.html  

• http://www.sciencephoto.com/media/115421/enlarge  

• http://www.gwc.maricopa.edu/class/bio201/Histology/HistoRev1a.htm  

• http://www.art.com/products/p360800391-­‐sa-­‐i4011216/gladden-­‐willis-­‐stratified-­‐squamous-­‐epithelium-­‐from-­‐the-­‐human-­‐mouth-­‐mucosa-­‐nonkeratinizing-­‐h-­‐e-­‐stain.htm  

• http://www.jeremyswan.com/anatomy/203/html/03i.html  

 

Tim  Fronek  tfronek@purdue.edu  Biology  Education  

   

The  skin  is  made  of  two  main  parts,  

the  epidermis  and  the  dermis.  The  

dermis  is  below  the  epidermis,  

diffuses  nutrients  to  the  epidermis,  

and  is  primarily  made  up  of  

adipose,  or  fat,  tissue.  The  epidermis  

is  mainly  composed  of  epithelial  cells,  

which  is  used  for  protection.  Epithelial  

cells  are  found  nearly  everywhere,  

inside  and  outside  of  your  body.  There  

are  four  types  of  epithelia  cells:  

squamous,  columnar,  cuboidal,  and  

psuedostratified.  However,  each  

epithelial  cell  can  arrange  in  a  different  

way.  If  there  is  one  layer  of  that  cell,  

then  it  is  called  simple.  For  example,  if  

there  was  one  layer  of  squamous  cells,  

it  would  be  called  simple  squamous.  If  

there  is  more  than  one  layer,  then  it  is  

called  stratified.    

 

Type  of  Epithelial  Cell  

Description   Simple  (side  by  side)  

Stratified  (stacked  on  top)  

 Squamous  

 Flat,  almost  looks  like  an  

egg.  

   

 Columnar  

Tall,  basically  a  3D  rectangle.  Stratified  

version  is  rare.  

   

 Cuboidal  

 Not  as  tall  as  columnar,  but  basically  a  cube  

   

   

Pseudostratified  

 Will  only  ever  have  one  layer.  The  prefix  psuedo-­‐means  “fake”,  hence  why  

it  looks  stratified  

   There  is  no  stratified  

version.  

 

The  epidermis  is  also  made  up  of  four  to  five  layers.  Thick  skin,  like  on  your  palms  and  feet,  have  five  layers,  and  thin  skin  only  has  four.  Starting  from  the  surface  and  going  down,  the  layers  are:  

Ø The  Stratum  Corneum-­‐Layers  of  dead  keratinized  (hardened)  cells.  Ø Stratum  Lucidum-­‐Only  found  in  thick  skin,  acts  as  more  protection  in  high  friction  

areas  Ø Stratum  Granulosum-­‐Produces  keratin  which  hardens  dead  skin  cells  for  

protection  Ø Stratum  Spinosum-­‐  Has  interlocking  spines  that  help  support  the  skin  Ø Stratum  Basale-­‐Constantly  dividing  layer  of  cells  that  push  cells  above  it  towards  

the  surface.  It  also  contains  melanocytes  that  produce  the  pigment,  melanin.