Skin Layers

The skin consists of 3 layers…each with their own structure and function.

  • The epidermis, is the outermost layer of skin and provides a waterproof barrier and creates our skin tone.
  • The dermis, beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands.
  • The deeper subcutaneous tissue or hypodermis, consists of fat and connective tissue

Epidermis
The epidermis is the outer layer of skin. The thickness of the epidermis varies in different types of skin. It is the thinnest on the eyelids at .05 mm and the thickest on the palms and soles at 1.5 mm.

The epidermis contains 5 layers. From bottom to top the layers are…

  • stratum basale
  • stratum spinosum
  • stratum granulosum
  • stratum licidum
  • stratum corneum

The bottom layer, the stratum basale, has cells that are shaped like columns. In this layer the cells divide and push already formed cells into higher layers. As the cells move into the higher layers, they flatten and eventually die.

The top layer of the epidermis, the stratum corneum, is made of dead, flat skin cells that shed about every 2 weeks.

There are also three types of specialized cells in the epidermis.

  • The melanocytes produce pigment (melanin)
  • The Langerhans’ cell is the frontline defense of the immune system in the skin
  • The Merkel’s cell’s function is open to debate

Dermis
The dermis also varies in thickness depending on the location of the skin. It is .3 mm on the eyelid and 3.0 mm on the back. The dermis is composed of three types of tissue that are present throughout – not in layers. The types of tissue are…

  • collagen
  • elastic tissue
  • reticular fibers

The dermis contains many specialized cells and structures.

  • The hair follicles are situated here with the erector pili muscle that attaches to each follicle.
  • Sebaceous (oil) glands and apocrine (scent) glands are associated with the follicle.
  • This layer also contains eccrine (sweat) glands, but they are not associated with hair follicles.
  • Blood vessels and nerves course through this layer. The nerves transmit sensations of pain, itch, and temperature.
  • There are also specialized nerve cells called Meissner’s and Vater-Pacini corpuscles that transmit the sensations of touch and pressure.
Hypodermis

  • This subcutaneous tissue is a layer of fat and connective tissue that houses larger blood vessels and nerves. 
  • this layer is important in the regulation of temperature of the skin itself and the body. 
  • The size of this layer varies throughout the body and from person to person. 
  • The main cell types are fibroblastsmacrophages and adipocytes ….(the hypodermis contains 50% of body fat…yes ladies…this is the culprit). Fat serves as padding and insulation for the body.

 

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