Support and Protection by the Integumentary System (Part 2)

• Integumentary System is the body's outer covering.
• Integumentary System protects the body and is the first line of barrier.
• Derivatives of the integumentary system include the hair, nail, and gland.
• Skin is the largest external organ.
• The three layers of the skin are epidermis, dermis, and hypodermis/subcutaneous.
• This is the outermost layer of the skin. Epidermis
• The five main layers of the epidermis:

  -Stratum corneum

  -Stratum lucidum

  -Stratum granulosum

  -Stratum spinosum

  -Stratum basale
• Stratum corneum is the uppermost multi-layer of dead, keratinized, cornified squamous cells.
• The cells in this layer are dead since there are no blood vessels found. Stratum corneum
• This layer of the epidermis contains keratin. Stratum corneum
• Keratin is a protein that acts as a waterproofing substance.
• This layer is said to be cornified and multi-layered. Stratum corneum
• Exfoliation is the process of shedding off.
• This layer continuously sheds off in a process called exfoliation. Stratum corneum
• Stratum lucidum is the layer which is only found in the thick skin.
• The thick skin includes the skin found in palms and soles in the foot. This layer provides additional thickness to these areas which are prone to shock and pressure. Stratum lucidum
• Stratum granulosum contains active keratinocytes.
• Keratonicytes are cells producing keratin.
• Stratum basale is the lowermost layer of the epidermis made up of one layer of columnar cells.
• This layer is the mitosis layer where cells are actively dividing giving rise to cells which will later on comprise the upper layers. Stratum basale
• This layer forms the nail and the hair. Stratum basale
• This layer contains melanocytes. Stratum basale
• cells that will produce melanin. Melanocytes
• Melanin is the substance responsible for skin pigmentation.
• Higher melanin production results to darker skin color while lower melanin production results to ligher skin color.
• Eumelanin, a type of melanin more photoprotective than pheomelanin, is present in higher quantities in dark skin and dark eyes than in light skin and eyes.
• Which layer of the skin is the site of Vitamin D Synthesis?

  Epidermis
• When exposed to UV rays from sunlight, the epidermis synthesizes a form of Vitamin D called cholecalciferol from a steroid cholesterol in the skin.
• This cholecalciferol will be converted into calcidiol in the liver.
• Calcidiol in the liver will be further converted into calcitriol in the kidney.
• Calcitriol is the active chemical form of the vitamin which is used by the body for the absorption of calcium and phosphorus which is needed for bone nourishment and repair.
• Dermis is the second layer of the skin which is found between the epidermis and hypodermis.
• This layer acts as the skin glue. Dermis
• Structures found in the dermis include:

  -abundant areolar connective tissue

  -blood vessel

  -sensory receptors

  -follicles and glands
• The abundant areolar connective tissue has elastin fibers which provide elasticity to the skin.
• Elastin fibers provide elasticity to the skin.
• Elastin fibers provide elasticity to the skin.
• Elasticity pertains to the property of the skin which resist change in shape and structure despite pressure and shock.
• Blood vessel includes the veins, arteries, and skin capillaries.
• Blood vessel includes the veins, arteries, and skin capillaries.