integumentary

• Skin cancer is the most common cancer worldwide and it is mainly caused by exposure to ultraviolet rays
• The most common source of ultraviolet rays is the sun
• Fair-skinned people


  More prone to developing skin cancer because they have less amount of melanin in their skin
• Dark-skinned people


  Have more protection against UV light
• Preventing skin cancer in fair-skinned people

  1. Limiting exposure to the sun

  2. Using sunscreens
• UVA


  Causes tanning and is associated with malignant melanoma
• UVB


  Causes sunburns
• Sunscreens should block both UVA and UVB rays to prevent sunburns and skin cancer
• Types of skin cancer

  • Basal cell carcinoma
  • Squamous cell carcinoma
  • Malignant melanoma
• Basal cell carcinoma


  • Looks like an innocent pimple
• Squamous cell carcinoma


  • Looks like a wound in the healing phase
• Malignant melanoma


  • Looks different from an ordinary mole
• Basal cell carcinoma


  Affects cells in the stratum, has the best prognosis and can be easily removed by surgery
• Squamous cell carcinoma


  Has a poorer prognosis and can cause death
• Malignant melanoma


  Rare but most dreaded, can easily metastasize and spread to other tissues
• The American Cancer Society developed a mnemonic (ABCD) to help identify moles at risk of developing into melanoma
• ABCD mnemonic


  A - Asymmetry, B - Border, C - Color, D - Diameter
• Subcutaneous tissue is the connecting tissue where skin is attached, it is not part of the skin
• Subcutaneous tissue


  Loose connective tissue which includes adipose (fat) tissue
• Adipose tissue in subcutaneous tissue varies with age, sex and diet
• Functions of adipose tissue


  Padding, insulation, estimating total body fat
• Skin has two main layers - epidermis and dermis, with subcutaneous tissue beneath
• Hair


  Found everywhere on human body except palms, soles, lips, nipples, genitalia, distal fingers/toes
• Hair follicle


  Imagination of epidermis extending into dermis, where hair arises from
• Hair shaft


  Expanded base of hair that protrudes from surface
• Hair cortex and medulla


  Hard outer layer and soft inner center of hair
• Hair cuticle


  Overlapping cells that hold hair in follicle
• Hair papilla


  Extension of dermis into hair bulb, contains blood supply for hair growth
• Hair growth cycle


  1. Growth stage

  2. Resting stage
• Hair fall is normal as long as it is not excessive
• Causes of excessive hair fall


  Products, stress, genetics
• Eyelashes have longer resting stage and shorter growth stage compared to scalp hair
• Melanin


  Determines hair color, decreases with age causing graying
• Erector pili muscle


  Smooth muscle attached to hair follicle, causes hair to stand on end (goosebumps)
• Sebaceous gland


  Major gland associated with hair follicles
• Pili muscle


  Erector pili muscle that causes the hair to stand on its end and become perpendicular to the skin surface
• Piloerection


  1. Contraction of erector pili muscle

  2. Causes goosebumps or "goose flesh"

  3. Activated by sympathetic response

  4. Can occur from cold, fear, or holding in
• Sebaceous gland


  Gland that produces an oily, white substance called sebum to lubricate the hair and skin
• Blocked sebum


  Can lead to acne or pimples
• Sweat glands


  • Eccrine sweat glands (coiled tubular, numerous, produce watery sweat for thermal regulation)
  • Apocrine sweat glands (join hair follicles, produce thicker secretions, become more active at puberty)