M4-5

• Integumentary system


  Consists of skin and accessory organs such as hair, glands, and nails
• Integumentary system


  • Protection
  • Sensation
  • Vitamin D production
  • Temperature regulation
  • Excretion
  • Prevents microorganisms
  • Reduces water loss -prevents dehydration
• Exposure to enough UV light can produce all the vitamin D needed by humans. However, people need to ingest vitamin D as well.
• Adequate levels of vitamin D are necessary because active vitamin D stimulates the small intestine to absorb calcium and phosphate. (essentials for bone growth and muscle function)
• Fatty fish (and fish oils) and vitamin D-fortified milk are the best sources of vitamin D.
• Body temperature normally is maintained at about 37°C (98.6°F)


  The rate of chemical reactions (metabolism) is altered by the changes in temperature
• To cool the body


  Blood vessels in dermis dilate and heat is transferred from deep in tissues to skin and sweat is produced
• Types of Heat Loss

  • Radiation - heat is lost through infrared energy
  • Convection - through air movement
  • Conduction - through direct contact with an object
• Skin


  Made up of two major tissue layers: epidermis and dermis
• Skin weighs approximately 9 lbs.
• Skin is usually referred to as "thin skin". "Thick skin" is found only on the palms of the hands and soles of feet.
• Epidermis


  • Most superficial
  • It rests on dermis
  • Lacks blood vessels
• Dermis


  • Most structural strength of skin is found in dermis
  • Skin rests on subcutaneous tissue (a connective tissue)
• Keratinization


  Cells become filled with the protein keratin, which makes the outer layer become more rigid and durable
• Epidermal Strata

  • Stratum Basale / Stratum Germinativum
  • Stratum Spinosum
  • Stratum Granulosum
  • Stratum Lucidum
  • Stratum Corneum
• Stratum Corneum


  • Outermost layer of epidermis
  • 20 to 30 layers of dead squamous cells filled with keratin & accounts for 75% of epidermal thickness
  • Joined by desmosomes
  • Coated and surrounded by lipid, which acts as waterproofing material
• Common Conditions associated with Stratum Corneum


  • Dandruff
  • Callus
  • Corn
• Keratinization


  A process in which new cells (with keratin) is pushing old cells to the surface. It takes 40 to 56 days for the new cells to reach the surface.
• Layers of Dermis

  • Papillary Layer
  • Reticular Layer
• Dermal Papillae


  • Projections found at the upper part of the dermis that extends to the epidermis
  • Blood flow through these vessels supplies nutrients, helps in removal of waste products, and regulates body temperature
• Determinants of Melanin Production

  • Genetic factors
  • Exposure to UV light
  • Hormones
• Areas with More Melanin

  • Freckles
  • Moles
  • Darkened areas in genitalia
  • Areola & nipples
  • Lips
  • Palms of hand
  • Soles of feet
• Cleavage Lines / Tension Lines


  Areas where skin is most resistant to stretching; caused by orientation of collagen fibers; vital in scarring
• Stretch Marks


  Visible lines through the epidermis that result from overstretched skin, for any reason, damaging the dermis; usually common when a person increases in size quite rapidly
• Albinism


  A recessive genetic problem that causes deficiency or an absence of melanin. People with this condition have fair skin, white hair and unpigmented irises in the eyes.
• Cyanosis


  A decrease in oxygen content in the blood produces bluish color of the skin
• Carotene


  Yellow pigment found in plants such as squash and carrots. It is lipid-soluble; when consumed, it accumulates in the lipids of the stratum corneum and in the adipocytes of the dermis and subcutaneous tissue.
• Subcutaneous Tissue


  • The subcutaneous tissue, which is not part of the skin, is sometimes called hypodermis
  • It is loose connective tissue, including adipose tissue that contains about half the body's stored lipids
  • The amount and location vary with age, sex, and diet
  • Adipose tissue in the subcutaneous tissue functions as padding and insulation
• Accessory Skin Structures

  • Hair
  • Glands
  • Nails
• Hair


  • Hair is produced in the hair bulb, which rests on the hair papilla
  • Blood vessels within the papilla supply the hair bulb with the nourishment needed to produce the hair
  • Hair is produced in cycles
  • Contraction of the arrector pili causes the hair to become more perpendicular to the skin's surface, or to "stand on end," and it produces a raised area of skin called a "goose bump"
• Hair Components

  • Hair Shaft
  • Hair Root
  • Hair Bulb
  • Hair Follicle
  • Hair Cortex
  • Hair Medulla
  • Hair Papilla
  • Arrector Pili
• Hair Papilla


  • Blood vessels within supply the hair bulb with nourishment needed to produce hair
• Hair Production


  Cycles
• Arrector Pili


  • Smooth muscle that surrounds each hair follicle
  • Contraction causes hair to become more perpendicular to skin's surface, producing "goose bumps"
• Hair Components

  • Hair Shaft - flexible strands of keratinized cells that protrude above skin surface
  • Hair Root - protrudes below skin surface
  • Hair Bulb - base of hair root where hair is produced
  • Hair Follicle - invagination of epidermis into dermis, group of cells that surround root and bulb
  • Hair Cortex - hard covering surrounded by cuticle
  • Hair Medulla - softer center surrounded by cortex
  • Hair Papilla - extension of dermis into hair bulb
  • Arrector Pili - smooth muscle surrounding hair follicle
• Testosterone and good nutrition promote hair growth
• Scalp hair grows for 3 years and rests for 1 year
• Eyelashes grow for 30 days and rest for 105 days
• Normally, we lose about 90 scalp hairs per day
• Hair color is determined by varying amounts and types of melanin. Grey hair is the loss or fading of melanin