Integumentary System

         The integumentary system is the makeup of the skin, which is in fact the body's largest organ.  There are three layers of the skin consist of the epidermis, dermis, and hypodermis.  The epidermis is the outermost layer that acts as a barrier and thus protection, it is actually made up of many layers of dead skin cells, kinda nasty! There are four or five distinct cells types that lie in this layer. These cell types are keratinocytes, meloncytes, merkel, and langerhans.  Keratinocytes produce the protein keratin.  Meloncytes produce the brown pigment melanin.  Langerhans help with the immune system and Merkel are associated with sensory  nerve endings.  The deepest layer of the Epidermis layer consists of one row of keratinocytes.  The layers of the Epidermis layer are Stratum Spinosum, Stratum Granulosum, Stratum Lucidum, Stratum Corneum-this is the outermost layer that protects from moisture and the basic environment effects.    

          Beneath this layer is the Dermis layer.  This layer is a strong flexible layer made up of connective tissue.  The Dermis is only made up of two layers versus the four of the epidermis, these layers are papillary and reticular.  Within these layers are cells such as fibroblasts, macrophages, and occasionally white blood cells.  The reticular layer of the Dermis makes up nearly 80% of the skin's thickness!  Since it is so thick it acts as a strong barrier of the skin that can stretch and recoil.  The papillary layer is also quite elastic.    

          Finally below this is the hypodermis layer, the deepest of the layers in the skin.  Within this layers is adipose and areolar connective tissue.  

          Skin Color is effected by three basic pigments.  Melanin is the reddish brown/black color which is seen in most darker skin colors.  However, it can also be seen in freckles and moles where there is a build up of melanin.  The pinkish orange color on palms and feet are from the pigment found in Carotene.  Blushing or flushing, usually seen in our faces from working hard or emotions is caused from Hemoglobin, a pinkish red pigment.
          Sweat glands are found all over the body, from head to toe, literally.  The glands found in the palms, feet and forehead are all eccrine sweat glands.  Cerimonious glands are found in the ear and secrete cerumen. Apocrine glands are found in the axillary and anogenital areas.  And finally the Mammary glands, that as the name suggests, secrete milk.  These four types of glands all help with keeping the body from overheating.  Sebaceous glands are found all over the body and control sebum, an oily secretion.  These glands just like many of the others can become clogged and result in a rather nasty cyst if not taken care of.  Skin changes as a human grows.  During teen years sweat glands often over work and result in excess oil in the skin thus creating acne.  As the become elderly these glands slow, often too much, and result in scaly rough skin.

Melanoma.  EW!

           Now let's take it into cancers of the skin.  There are three major types of skin cancer Basal cell carcinoma, Squamous cell carcinoma, and Melanoma.  Basal is the most common of these three types.  This type of cancer takes over the dermis and hypodermic layers.  However, since it's slow growing and doesn't metastasize (spread) it can be cured quite easily with surgery.  Squamous cell carcinoma comes from keratinocytes of stratum spinosum.  It is found in the ears, around the mouth, and scalp.  This cancer unlike Basal grows very quickly and spreads if not taken care of.  This can be taken care of surgericaly or through radiation therapy.  Finally, there is Melanoma, the most serious and dangerous type of skin cancers.  Melanomas can be distinguished by their color, size, texture, and shape.  This type of cancer is highly metastatic and is resistant to chemotherapy.  There are some treatments that involve surgery and immunotherapy however, the chance of survival is low, especially depending on the size.
          Not only must the skin protect the body from the environment and face the possibility of cancer it must also take on the idea of burns.  Burns range in degree from 1-3.  Most everyone has endured a first degree burn that only damages the epidermis.  In second degree burns the epidermis and small portions of the dermis are damaged.  Third degree however, is where it gets nasty.  The entire thickness of the skin is damaged.  The skin is basically destroyed and takes ages to restore itself.  In third degree burns infection is the most important thing to worry about.

        Hair on the body is similar to much of the skin, in the since that, it's dead.  Hair is actually dead strands of keratinized cells produced by hair follicles.  Hair follicles project from an embedded root in the skin.  The center of the root is called the medulla, then the cortex and finally the outermost cuticle.  Hair is naturally colored at the bottom by melanocytes.  Hair helps with warmth as well as protection from environmental effects like sunlight, heat loss, insects etc.   And lets face it, hair is very important in physical appearance!  Which is why balding, or Alopecia is rather sad.  It is natural however, for human's  hair to become thin and fall out as they become elderly.
          The Integumentary system is obviously a huge part of the human body.  It protects against the harmful rays of the sun, fights against infection, helps regulate temperature, and really, holds us all together.  Keep it healthy!