The Integumentary Summary

From Ludwig's Integumentary notes.

Skin color comes from melanin, carotene, and hemoglobin.  Melanin is produced and gives the skin a darker more tan color.  Carotene is the yellow orange pigment of the skin and hemoglobin is the reddish pigment.  Different glands in the skin keep the skin from overheating or keep our skin soft.  Sweat glands in our bodies secrete cerumen and milk.  The sebaceous glands are found all over the body and soften skin when they're stimulated by hormones by secreting an oily substance called sebum.The skin has three awesome layers.  The epidermis is the outermost layer of the skin.  It's the stratified layer filled with keratinocytes, melanocytes, Merkel cells, and Langerhans cells.  Under that lies the dermis.  This layer is much thicker than the epidermis.  Most cells here are fibroblasts, macrophages, and white blood cells.  The dermis also has two layers in itself, the papillary and reticular layers.  The last layer of the skin is the hypodermis.  It's composed of adipose and areolar connective tissue.
The hair and nails are also part of the integumentary system.  Hair keeps the body warm.  It is made of dead keratinized cells and colored by melanocytes at the base of the hair.  Nails are simply a modification of the epidermis.

Now for the fun stuff.

Melanoma image from Skinipedia.

The major types of skin cancer are melanoma, squamous cell carcinoma, and basal cell carcinoma.
Melanoma is the most dangerous type of skin cancer.  It's very malignant and people often mistake it for a birthmark, or vice versa.
The way to tell if a spot is melanoma is to check it with the ABCD rule.  Assymetry, Border, Color, and Diameter.  A spot of melanoma will be asymmetrical.  The border will be jagged and uneven.  The color of melanoma is much darker than a normal birthmark and can sometimes be shades of red or blue.  And if the diameter is bigger than 6mm, which is about the size of a pencil eraser, then you should get the spot checked for melanoma.  Melanoma is usually treated by removing the spot, but if it's 4mm thick into the epidermis then chances of survival are very low.

Third degree burn from burn remedies.com.  Ouch...

Being on the outside of our bodies our skin is also susceptible to burns.  First degree burns are just a red mark that only damages the epidermis.  Second degree burns damage through the epidermis and into the upper regions of the dermis.  They look a lot like first degree burns but may also blister.  Third degree burns damage through the entire thickness of the skin.  They don't hurt very much because nerve endings have been damaged and they are generally bright red, black, or ashy white.  Doctors and nurses use the rule of nines to estimate the severity of burns.  Burns are severe if 25% of the body has second degree burns, 10% of the body has third degree burns, or if third degree burns are on the hands, face, or feet.  One of the major dangers of burns is dehydration.

The integumentary system is a massive and rather complicated thing.  There are a lot of dangers to the skin but somehow everything works out all right.  Usually.