Support and Protection by the Integumentary System

• Integumentary System


  • Forms body’s outer covering

  • Primarily functions in protecting the body

  • Composed of skin and its derivatives: hairs, nails, and glands

  > Skin & secretions – 1st line of barrier defense

  • Different functions: sensation, thermoregulation, vitamin D synthesis, excretion and osmoregulation
• Integumentary System


  Organs of the Integumentary System

  A. Skin

  B. Hair

  C. Nails

  D. Glands
• 1. Skin


  • Largest external organ of the body

  • Functions:

  > External surface protection, covering, sensation, thermoregulation, vitamin D synthesis, excretion, and osmoregulation

  > Waterproofing

  > Formation of hair and nails

  > Responsible for natural skin color

  • 3 main layers:

  > Epidermis

  > Dermis

  > Hypodermis (subcutaneous)
• A. Skin


  Layers of the epidermis

  1. Stratum corneum

  2. Stratum lucidum

  3. Stratum granulosum

  4. Stratum spinosum

  5. Stratum basale

  
• Layers of the epidermis

  Stratum corneum

  • Uppermost multi-layer of dead keratinized, cornified squamous cells

  • No blood vessels --> dead cell layer

  • Keratin – waterproofing substance

  • Cornified – multi-layered

  • Exfoliation – continuous shedding

  
• Layers of the epidermis

  2. Stratum lucidum

  • Only found in thick skin (skin in palm & soles of feet)

  • Provides additional thickness to areas prone to shock and pressure

  
• Layers of the epidermis


  3. Stratum granulosum

  • has active keratinocytes (cells producing keratin)

  
• Layer of Epidermis


  4. Stratum spinosum

  • composed of spiny-shaped cells (spinosum is Latin for spiny) contributes to the strength and flexibility of the skin

  
• Layers of the epidermis


  5. Stratum basale

  • Lowermost layer; one layer of columnar cells

  • Mitosis layer – cells are actively dividing -->give rise to cells of the upper layers

  • Forms the nails & hair

  
• Layers of Epidermis


  5. Stratum basale

  • Contains melanocytes (produce melanin)

  > Melanin – substance for skin pigmentation

  > UV rays protection

  > scatter UV rays and consume free radicals induced by light

  • Vitamin D synthesis

  • Exposure to UV rays --> for absorption of calcium & phosphorus, needed for bone nourishment & repair
• A. Skin(2nd layer)

  Dermis

  • 2nd layer of skin found in between epidermis and hypodermis

  • Acts as skin glue
• A. Skin 


  Dermis

  • Functions:

  • Provides elasticity of skin

  • Nourishes epidermis

  • Receives sensory stimulation

  • Forms unchanging fingerprint and footprint

  > Unique identity

  > Easy grasping without slippage
• A. Skin 


  Structures in the Dermis

  1. Abundant areolar connective tissue
  2. Blood vessel
  3. Sensory receptors
  4. Follicles and glands
• Structures in the Dermis


  1. Abundant areolar connective tissue

  • Has elastin fibers --> elasticity to skin

  • Elasticity – pertains to property of skin which resists change in shape & structure despite pressure and shock
• Structures in the dermis


  2. Blood vessel

  • Veins, arteries, and skin capillaries

  • Provide nourishment to skin cells

  • Thermoregulatory functions:

  > High body temperature --> blood vessels dilate --> extra heat

  escapes thru skin

  > Low body temperature --> blood vessels constrict --> internal

  body organs utilize heat flowing within blood vessels

  
• Structures in the Dermis


  3. Sensory receptors

  • In the form of naked dendrites encapsulated by connective tissue
  • Mechanoreceptors – sense physical deformation (i.e., pressure, touch, stretch, and motion)
  • Thermoreceptors – detect heat & cold
  • Pain receptors/nociceptors – detect harmful conditions (thermal, mechanical, or chemical stimuli)

  
• A. Skin


  Hypodermis/subcutaneous

  • Lowermost layer of the skin
  • Made up of fats & adipose tissue
  • Thinnest in the eyelids and thickest in buttocks (for females) and tummy (for males)
  • Functions:

  • Provides high energy reserve

  • Provides insulation

  • Provides cushion
• 2. Hair


  • Produced by basale cells of the skin
  • Made up of keratin protein and cuticle
  • 2 main parts:

  • hair root – attached to arrector pili muscle (raises hair upon contraction --> goosebumps)

  • hair shaft
• 2. Hair


  Functions:

  • Thermoregulation
  • Protection
  • Sensation
• Functions of Hair


  • Thermoregulation

  • Provides additional insulation to the body

  • Too cold --> hair is raised for additional layer of insulation (thru

  arrector pili muscle)
• Functions of Hair


  • Protection

  • Modified into defensive structures in some animals (quills & spikes)
• Functions of Hair


  • Sensation

  • Hair movement can be sensed by mechanoreceptors in skin
• 3. Nails

  Nails

  • Made up of cuticle and keratin
  • 2 main parts: nail body/plate & nail root
  • Main function: protect toes & fingers
  • Also for:

  • grasping small objects

  • Modified into defensive structure (claw)

  • Changes color, shape, thickness, or texture may

  reflect abnormalities in human body
• 4. Glands


  2 types of skin glands

  • Sweat Glands
  • Modified Sweat Glands
• Types of Skin Glands

  • Sweat glands – coiled tubule-like type of exocrine gland

  • Duct opens into skin surface

  • Secrete sweat (mixture of water, ions, N wastes, sometimes proteins)

  • 2 types of sweat glands:

  > Eccrine sweat gland

  > Apocrine sweat gland
• Types of Sweat Glands


  Eccrine sweat gland

  • found almost everywhere

  • secretion mainly composed of water, some NaCl, urea, uric acid, & K+

  • Function: thermoregulation & excretion
• Types of Sweat Glands


  Apocrine sweat gland

  • Found only on some areas like armpit and ano-genital area

  • Active during puberty, emotional stress, & sexual stimulation

  • Secretion composition: water, proteins, amino acids
• Types of Skin Glands


  Modified sweat glands

  • Ceruminous glands –secrete earwax (trap foreign molecules in ear canal)
  • Ciliary glands – produce tear-like substance which lubricates & protects eyes
  • Mammary glands – secrete milk for infant nourishment