integumentary

• Integumentary System


  Consists of the skin, and accessory structures such as hair, glands, and nails
• Functions of the Integumentary System


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


  Most superficial layer, stratified squamous epithelium, mitosis occurs in deepest layers
• Keratinization


  Transformation of the living cells of the stratum basale into the dead squamous cells of the stratum corneum
• Stratum basale


  Deepest layer, cuboidal & columnar cells, undergo mitosis every 19 days
• Stratum corneum


  Most superficial stratum, dead squamous cells filled with keratin, lipids, joined by desmosomes
• Callus


  Thickened area
• Corn


  Bony prominence, thickened corn shaped structure
• Dermis


  Dense collagenous connective tissue, contains fibroblasts, adipocytes, macrophages, nerves, hair follicles, smooth muscles, glands, lymphatic vessels
• Collagen and elastic fibers


  Provide structural strength
• Cleavage lines/Tension lines


  Collagen fibers are oriented in some directions, skin is most resistant to stretch along these lines
• Stretch marks


  Skin is overstretched, leaving lines that are visible
• Dermal papillae


  Contain blood vessels that supply the epidermis with nutrients, remove waste products, and regulate body temperature
• Melanin


  Pigments responsible for skin, hair, eye color
• Melanin pigments


  • Yellow (Caucasian)
  • Brown (Asians)
  • Black (African)
• Melanocytes


  Produce melanin, irregularly shaped cells in the stratum basale
• Melanosomes


  Vesicles derived from the Golgi apparatus where melanin is produced
• Factors of Melanin Production


  • Genetic factors
  • Exposure to UV light
  • Hormones
• Albinism


  Recessive genetic trait that causes deficiency / absence of melanin
• Cyanosis


  Bluish skin color, decreased blood oxygen
• Carotene


  Yellow pigment in plants, source of vitamin A
• Birthmarks


  Congenital disorder of the capillaries in the dermis
• Subcutaneous Tissue


  Attaches the skin to underlying bones, also called the hypodermis, loose connective tissue, storage of body fat
• Hair


  Columns of dead, keratinized epithelial cells, produced in the hair bulb
• Hair Structures


  • Hair follicle
  • Shaft
  • Root
  • Hair bulb
  • Cortex
  • Medulla
  • Cuticle
• Hair Growth


  Hair is formed by epithelial cells within the hair bulb, divide and undergo keratinization, hair root + shaft = columns of dead keratinized epithelial cells
• Hair Resting Stage


  Growth stops, hair is held in the hair follicle
• Next Hair Growth Stage


  A new hair is formed, the old hair falls out
• Eyelashes


  Grow for about 30 days, rest for 105 days
• Scalp hairs


  Grow for 3 years, rest for 1 - 2 years
• Arrector Pili


  Smooth muscles, contraction = hair to stand on end, produces goose bumps
• Sebaceous Glands


  Simple, branched acinar glands, connected by a duct to the superficial part of the hair follicle, secrete sebum - oily, white substance rich in lipids, lubricates the hair/surface of the skin
• Eccrine Sweat Glands


  Simple, coiled, tubular glands, release sweat by melocrine secretion, numerous in the palms and soles
• Apocrine Sweat Glands


  Simple, coiled, tubular glands, produce a thick secretion rich in organic substances, released primarily by melocrine secretion, some glands demonstrate holocrine secretion, open into hair follicles in armpits and genitalia, become active at puberty
• Ceruminous Glands


  Secrete cerumen (earwax)
• Mammary Glands


  Secrete milk
• Nails


  Dead stratum corneum cells, contain a very hard type of keratin
• Nail Structures


  • Nail body
  • Nail root
  • Cuticle
  • Nail matrix
  • Nail bed
  • Lunula
• Protection Function of the Integumentary System


  • Reducing water loss, prevents microorganisms from entering the body, protects underlying structures against abrasion, hair on head = insulator, eyebrows = keep sweat out of the eyes, eyelashes = protects the eyes from foreign objects, hair in the nose, ears = prevents the entry of dust, nails = protect the ends of the fingers, toes from damage; can be used in defense
• Sensation Function of the Integumentary System


  • Sensory receptors for pain, touch, hot, cold, pressure