Dermis

Dermis

1. It is a strong, stretchy envelope that helps to bind the body together

   • When you buy leather goods, you're buying treated dermis of animals

2. Dermis varies in thickness

   • thick on the palms and soles but thin on the eyelids

3. Collagen and elastic fibers are found in the dermis

   • Collagen fibers
     • Responsible for the toughness of of the dermis, they also attract and bind water and thus keep the skin hydrated
   • Elastic Fibers
     • Give the skin its elasticity when we are young. As we age, the number of collagen and elastic decreases and subcutaneous tissue loses fat
       • As a result, the skin looses its elasticity and begins to sag and wrinkle

4. Abundantly supplied with blood vessels that play a role in maintaining body temperature homeostasis

   • High body temperature
     • capillaries of the dermis become swollen with heated blood and the skin becomes reddened and warm, which allows body heat to radiate from the skin surface
   • Cool body temperature
     • Blood bypasses the dermis capillaries temporarily, allowing internal body temperature to stay high

5. 2 layers made by the dense connective tissue

   • Papillary Layer
     • upper dermal region. It is uneven
     • Dermal Papillae
       • peglike projections in the superior surface
       • Contain capillary loops, which furnish nutrients to the epidermis
       • House pain receptors (free nerve endings) and touch receptors
       • On the palms of the hands and soles of the feet, the papillae are arranged in definite patterns that form looped and whorled ridges on the epidermal surface that increase friction and enhance the gripping ability of the fingers and feet
       • Papillary patterns are genetically determined
         • The ridges of the fingertips are well provided with sweat pores and leave unique, identifying films of sweat called fingertips on anything you touch
   • Reticular layer
     • Deepest skin layer
     • Contains irregularly arranged connective tissue fibers
       • As well as blood vessels, sweat and oil glands, and deep pressure receptors called lamellar corpuscles
     • Phagocytes found here act to prevent bacteria that have managed to get through the epidermis from penetrating any deeper into the body

6. Rich nerve supply

   • many of the nerve endings have specialized receptor end-organs that send messages to the central nervous system for interpretations when they are stimulated by environmental factors