INTEGUMENTARY SYSTEM

• Skin


  It is also known as Integument (covering) and Cutaneous Layer
• Skin


  The largest single organ in the body
• 15%-20%


  The total body weight of skin
• 5 functions of the SKIN

  1. Protection
  2. Sensory
  3. Thermoregulatory
  4. Mechanoreceptors
  5. Sexual Signaling
• Thick and Thin Skin


  2 types of SKIN
• Thick skin


  A type of SKIN that covers the palms and soles and varies from 400 to 1400 μm (1.4mm)
• Thin skin


  A type of SKIN covers the whole body except the palms and the soles and varies from 75 to 150 μm
• 3 general layers of the skin:

  • Epidermis
  • Dermis
  • Hypodermis
• Epidermis


  One of the general layers of the skin that is an epithelial layer of ectodermal origin
• Dermis


  One of the general layers of the skin that is a layer of mesodermal connective tissue
• Subcutaneous layer


  One of the general layers of the skin that consists of loose connective tissue layer usually containing pads of adipocytes
• Hypodermis


  Another term for subcutaneous layer
• Epidermis


  Its primary tissue composition is keratinized stratified squamous epithelium. It lacks vasculature and only receives nutrients only from the dermis
• 4 cells in the EPIDERMIS:

  • Keratinocytes
  • Melanocytes
  • Langerhans Cells
  • Merkel Cells
• Keratinocytes


  The primary cell located at the epidermis
• Keratinocytes


  Originate in the deepest layer of the epidermis, the stratum basale and move up to the final barrier layer of the skin, the stratum corneum.
• Melanocytes


  A pigment-producing cell located at basal epidermis (stratum basale) and is derived from the neural crest
• Melanocytes


  A pale-staining, rounded CELL bodies that synthesize dark MELANIN pigment in melanosomes which protects nuclear DNA from UV damage.
• 2 types of melanin:

  • Eumelanin
  • Pheomelanin
• Albinism


  A congenital disorder due to skin hypopigmentation due to the defect of the enzyme tyrosinase which is necessary for synthesizing melanin pigment
• Vitiligo


  An abnormal skin condition which is an autoimmune disorder that causes white patches of the skin due to loss or decreased activity of melanocytes
• Langerhans Cells


  APCs (Antigen Presenting Cells) and macrophages, which are found in the skin, comprise 2-8% of cells in the epidermis.
• Langerhans Cells


  A cell located at spinous layer of epidermis that bind, process, and present antigens to T-lymphocytes
• Merkel Cells is also known Epithelial Tactile Cells
• Merkel cells


  A cell that is a mechanoreceptors for light touch (sensory) and abundant in fingertips and bases of some hair follicles
• Merkel cells


  A cell characterized by small, Golgi-derived dense-core neurosecretory granules containing peptides.
• 5 Layers of Epidermis (in order)

  • Stratum Corneum
  • Stratum Lucidum
  • Stratum Granulosum
  • Stratum Spinosum
  • Stratum Basale
• Stratum Corneum


  Most superficial layer of epidermis that provide protection against friction and water loss
• 15 to 20 layers


  How many layers does Stratum Corneum have?
• Stratum Corneum has 15-20 layers of dead, flattened, anucleate, keratin-filled keratinocytes called squames
• Stratum Lucidum


  Second layer of epidermis that can only be found on THICK skin
• Stratum Lucidum has 2-3 layers of anucleate and dead keratinocytes
• Stratum Granulosum


  The darkest stained layer (dark purple) that contains kerato-hyaline granules and lamellar granules
• Stratum Granulosum has 3-5 layers of keratinocytes
• kerato-hyaline granules and lamellar granules


  Two granules found in Stratum Granulosum
• Stratum Spinosum


  The thickest layer of epidermis consists of generally polyhedral cells having central nuclei with nucleoli and cytoplasm actively synthesizing keratins.
• Langerhans cell


  The cell present in Stratum Spinosum
• The Stratum Spinosum contains keratin filament bundles which is called Tonofibrils
• Stratum Spinosum contains several layers of keratinocytes all joined by desmosomes which also contain tonofibrils that adhere to the desmosomes leading to the appearance of many short spine or prickles at the cell surfaces
• Stratum Germinativum


  Another term for Stratum Spinosum