Integumentary System

• The integumentary system consists of the skin and accessory structures, such as hair, glands, and nails

  
• Integumentary System


  • Forms the boundary between the body and the external environment, thereby separating us from the external environment while allowing us to interact with it
• Major functions of the integumentary system

  • Protection
  • Excretion
  • Sensation
  • Temperature regulation
  • Vitamin D production
• Protection


  • Protects underlying structures from mechanical damage or abrasion
  • Reduces the negative and harmful effects of ultraviolet light
  • Keeps microorganisms and toxic substances from entering the body
  • Reduces water loss from the body, preventing dehydration
• Excretion


  Small amounts of waste products, such as urea, uric acid, and ammonia, are excreted through the skin and glands
• Sensation


  Acts as sense organ; has sensory receptors that can detect heat, cold, touch, pressure, and pain
• Temperature regulation


  • The modulation in the amount of blood flow through the skin and the activity of sweat glands contribute to temperature regulation
  • Blood vessels dilate when it is hot and constrict when it is cold
  • Sweat glands produce sweat when it is hot and stop sweat production when it is cold

  
• Vitamin D production


  When exposed to ultraviolet light, the skin produces a molecule (7-dehydrocholesterol) that can be transformed into vitamin D, an important regulator of calcium homeostasis
• Layers of the skin

  • Epidermis
  • Dermis
  • Hypodermis (Subcutaneous tissue)

  
• Epidermis

  • The uppermost layer of the skin; approximately 0.04 to 1.5 mm thick

  
• Layers of the epidermis

  • Stratum Germinativum (Basale)
  • Stratum Spinosum
  • Stratum Granulosum
  • Stratum Lucidum
  • Stratum Corneum
• Stratum Germinativum (Basale)


  • Deepest stratum of the epidermis; single layer of cuboidal or columnar cells
  • Produces cells of the most superficial strata; melanocytes produce and contribute melanin, which protects against ultraviolet light
• Stratum Spinosum


  • Spine-like appearance cells; 8–10 layers of many-sided cells
  • Produces keratin fibers; lamellar bodies form inside keratinocytes
• Stratum Granulosum


  • Two to five layers of flattened, diamond-shaped
  • Produces keratohyalin granules; lamellar bodies release lipids from cells
  • Cells die - loss of nuclei and cellular contents except keratin filament and matrix materials
• Stratum Lucidum


  • Three to five layers of dead cells; appears transparent
  • Present in thick skin (skin on palms and soles), absent in most thin skin
• Stratum Corneum


  • Most superficial stratum of the epidermis; 25 or more layers of dead squamous cells
  • Loss of cell nuclei and all cellular contents except keratin filaments and matrix materials of granular cell
  • Provides structural strength due to keratin within cells; prevents water loss due to lipids surrounding cells; sloughing off of most superficial cells resists abrasion
• Melanin


  • Provides skin color
  • absorbs harmful UV radiation
  • produced in melanocytes
• Dermis


  • Deep part of skin; connective tissue composed of two layers - papillary layer and reticular layer
  • Composed mainly of dense collagenous fibers—responsible for its elasticity and durability
  • With blood vessels; contains fats, nerves, smooth muscles, hair follicles, and glands
  • Cells of the dermis: Fibroblast, Macrophages, Mast cells, Lymphocytes

  
• Layers of the dermis

  • Papillary Layer
  • Reticular Layer

  
• Papillary Layer


  • Loose connective tissue; brings blood vessels close to the epidermis
  • Contains dermal papillae - projections that extend to the epidermis and form curving ridges into fingerprints and footprints; increase friction and improve grip
  • Brings blood vessels close to the epidermis

  
• Reticular Layer


  • Mat of collagen and elastic fibers; dense irregular connective tissue
  • Main fibrous layer of the dermis; strong in many directions; forms cleavage lines
  • Contains glands and hair follicle

  
• Hypodermis / Subcutaneous Layer


  • Not part of the skin; loose connective tissue with abundant deposits of adipose tissue
  • Attaches skin to the underlying structure (bones and muscles)
  • Adipose tissue provides energy storage, insulation, and padding; blood vessels and nerves from the subcutaneous tissue supply the dermis

  
• Accessory skin structures

  • Hair
  • Glands
  • Nails

  
• Hair on the Head


  • acts as a heat insulator and protects against ultraviolet light and abrasion
• Skin glands

  • Sebaceous glands
  • Sweat glands
  • Ceruminous glands
  • Mammary glands
• Sebaceous glands


  Secretes an oily substance called sebum that is made of fat (lipids) and the debris of dead fat-producing cells, for lubricating hair and prevents skin drying
• Eccrine Sweat Gland

  • present everywhere but numerous in palms and soles; secretes mostly water and salts; for temperature regulation
• Nails


  • A thin plate of dead, keratinized stratum corneum cells
  • They grow continuously and serves as a protective plate and enhances sensation of the fingertip

  
• Partial-thickness burns damage only the epidermis (first-degree burn) or the epidermis and the dermis (second-degree burn)
• Full-thickness burns (third-degree burns) destroy the epidermis, the dermis, and usually underlying tissues
• As the body ages, blood flow to the skin declines, the skin becomes thinner, and elasticity is lost
• Sebaceous and sweat glands become less active, and the number of melanocytes decreases
• Eyebrows

  • Keep sweat out of the eyes
• Axillary and Pubic Hair

  • a sign of sexual maturity and protect against abrasion
• Three parts of hair

  • shaft, root, and hair bulb.
• Root and Shaft of Hair

  • composed of dead keratinized epithelial cells.
• Hair Bulb

  • produces the hair in cycles, with a growth stage and a resting stage
• What determined hair color

  • Hair color is determined by the amount and kind of melanin present
• Eyelashes

  protect the eyes from foreign objects
• hair in the nose and ears

  prevents dust and other materials from entering