Integumentary System

• General Characteristic of Integumentary System:

  • Integument/ Cutaneous layer
  • Largest single organ of the body
  • 15-20% of total body weight
• Functions of skin:

  • Protection
  • Sensory
  • Thermoregulatory
  • Metabolic
  • Sexual signaling
• It covers the palms and soles (400 to 1400 micrometer)

  Thick skin
• It covers the whole body except palms and soles (varies from 75 to 150 micrometer)

  Thin skin
• Characteristics of Epidermis:

  • Stratified squamous keratinized epithelium
  • lack vasculature
  • receive nutrients from the dermis
• Keratinocyte

  • Primary cells
  • Located at the epidermis
  • Originate the stratum basale and move up to the final barrier of the skin, stratum corneum
• Melanocyte:

  • Located at the basal epidermis
  • Neutral crest derived
  • Pale-staining, rounded cell bodies
  • Synthesizes dark melanin pigment in melanosomes
  • Protects nuclear DNA from UV damage
  • Disease related to melanocyte: Albinism and vitiligo
• It is brown or black pigment; found in hair follicle

  Eumelanin
• Termed as red hair

  Pheomelanin
• A condition wherein the less melanin than usual in the body; condition that leads to having very light skin, hair and eyes.

  Albinism
• It is due to defect in the enzyme tyrosinase


  Albinism
• A disorder that cause patches of skin to lose pigment or color; happens when melanocyte are attaked and destroyed

  Vitiligo
• Three general layers of the skin:

  Epidermis

  Dermis

  Hypodermis (subcutaneous layer)
• What are the cells present in epidermis?

  Keratinocyte

  Melanocyte

  Langerhans

  Merkel cell
• Responsible for sensing gentle touch?

  Merkel cell
• What is the pigment that produced by melanocyte?

  melanin
• It is decrease activity of melanocyte

  Vitiligo
• Where does the langerhans cell located?

  Stratum spinosum
• Langerhan cells:

  • Antigenic presenting cell
  • 2-8% of cells in epidermis
  • Bind, process and present antigen to T-lymphocytes
• Aka Epithelial Tactile Cells

  Merkel cells
• Merkel cells:

  • Mechanoreceptors for light touch
  • Abundant in fingertips and bases of some hair follicles
  • Small, golgi-derived dense-core neurosecretory granules containing peptides
• Where does the melanocyte is located?

  basal epidermis or stratum basale
• Neural crest derived

  Melanocyte
• Layers of the Epidermis:

  All layers have thick and thin skin except Stratum lucidum which has thick skin only.
• Enumerate the layers of the epidermis:

  1. Stratum corneum
  2. Stratum lucidum
  3. Stratum granulosum
  4. Stratum spinosum
  5. Stratum basale
• It is keratin-filled keratinocyte

  squames
• Stratum corneum:

  • 15-20 layer of dead, flattened, anucleate, keratin-filled called squames
  • Layer of dead keratinocytes
  • Bound by hydrophobic lipid-rich segment which provides protection against water loss and friction
• What are the layers of skin that have function of protection of Water loss?

  Stratum corneum and Stratum granulosum
• What are the functions of squames?

  Protection for friction and water loss
• How many layers of anucleate dead cells in stratum lucidum?

  2-3 layers
• Stratum granulosum:

  • 3-5 layers of keratinocyte
  • Contains kerato-hyaline granules
  • intensely basophilic
  • Contains lamellar granules which produces lipid-rich impermeable for barrier against water loss
• It is lipid-rich impermeable layer around the cells forming a major part of the skin's barrier against water loss

  lamellar granules
• Considered as thickest layer among stratums

  Stratum spinosum
• Stratum spinosum:

  • Thickest layer
  • Consists polyhedral cells having central nuclei with nucleoli and cytoplasm actively synthesizing keratins
  • Several layers of keratinocyte all joined by desmosomes
  • Contains tonofibrils, prickle cells
  • Cells may still divide
  • Contains Stratum germinativum
• It binds to our desmosomes thus forming spines between keratinocytes in the stratum spinosum

  tonofibrils
• Structure present in the stratum spinosum that causes keratin or prickle

  tonofibrils
• Keratinocytes in our stratum spinosum

  Prickle cell
• Where does mitosis occurs?

  Stratum basale
• Stratum basale:

  • Single layer of cuboidal to low columnar cells in contact with basement membrane
  • Mitosis occurs
  • Melanocytes and Merkel cell also present
• Where does merkel and melanocyte are present?

  Stratum basale