• The epidermis
• The dermis 
• The subcutaneous tissue
  

The Epidermis

• The uppermost layer of the skin 0.1 to 1.5 mm thick . It is made up of five layers.
• basal cell layer contains a pigment melanin
• squamous cell layer contain cells called langerhans which latch on to invading antigens ,and alert the immune system to their presence 
• the stratum granulosum these cells migrate to the upper layer to replace the dead cells 
• the stratum lucidum these cells migrate to the upper layer to replace the dead cells 
• stratum corneum it is the outermost layer containing 10 to 30 layers of dead cell

The Dermis

• It lies below the epidermis and is 1.5 to 4 mm thick 
• It consists of oil glands, hair follicles and nerve endings
• Also consists of blood and lymph vessels collagen (tough, insoluble protein that holds the muscles and organs together) and elastin (keeps the skin elastic)
• Its major components are sweat glands of two types:
  • apocrine glands found only in the armpits and the pubic areas. 
  • eccrine glands are found all over the body and they regulate the body temperature.

The Subcutaneous Tissue

• The deepest layer of the skin 
• Acts as the insulator, conserving body heat as a shock absorber, protecting internal organs from injury 
• Stores energy reserve.
• The blood vessels, nerves, lymph vessels, and hair follicles also cross through this layer 
  

The Functions of Skin

• Acts as a barrier 
• First line of defense against bacteria, parasites and other organisms 
• Regulates temperature by increasing or decreasing sweat 
• Gathers information about the surroundings alters us to dangers and allows us to feel pleasure as well as pain.
• Produces vitamin D
• Reflects the negative effects of smoking and alcohol drug use and stress
• Many diseases show symptoms on the skin e.g. chickenpox, jaundice etc.