ch 5 the integumentary system
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Ch. 5 The Integumentary System

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Ch. 5 The Integumentary System. Introduction. Integument consists of: Skin – largest organ Accessory structures (hair/sweat glands) Subcutaneous tissue Skin Barrier to many harmful substances. The Skin. 2 major layers (Fig. 5-1) Epidermis – outer layer Dermis – inner layer.

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introduction
Introduction
  • Integument consists of:
    • Skin – largest organ
    • Accessory structures (hair/sweat glands)
    • Subcutaneous tissue
  • Skin
    • Barrier to many harmful substances
the skin
The Skin
  • 2 major layers (Fig. 5-1)
    • Epidermis – outer layer
    • Dermis – inner layer
epidermis
Epidermis
  • Stratified squamous keratinizing epithelium
  • Thickest on palms, soles
  • Abundant keratinocytes
  • No capillaries
  • 2 sublayers
    • inner stratum germinativum
    • outer stratum corneum
stratum germinativum
Stratum Germinativum
  • “stratum basale”
  • Base of the epidermis where mitosis occurs
    • older cells pushed toward skin surface
      • produce keratin and die
  • Merkel cells (Merkel discs)
    • touch receptors (Fig. 5-2)
stratum germinativum1
Stratum Germinativum
  • Keratinocytes
    • living cells that synthesize antimicrobial “defensins”
      • rupture pathogen membranes as part of inflammatory process
  • Living portion produces vitamin D when exposed to sunlight
stratum corneum
Stratum Corneum
  • Outermost epidermal layer
  • Keratin prevents evaporation and water entry
  • Barrier to pathogens & chemicals
langerhans cells
Langerhans Cells
  • “dendritic cells” (Fig. 5-2)
  • Originate in red bone marrow
  • Phagocytize foreign material
    • migrate to lymph nodes; take pathogen to lymphocytes
      • triggers immune response
melanocytes
Melanocytes
  • See Fig. 5-2
  • Produce melanin
    • those with darker skin produce large amounts
    • production increased in when exposed to UV rays
  • Melanin gives color to hair, iris, choroid layer of eye
  • See Table 5-1
dermis
Dermis
  • Made of irregular fibrous connective tissue
    • fibroblasts produce collagen & elastic fibers
      • allow strength & elasticity
  • Papillary layer – junction of dermis with epidermis (Fig. 5-1)
    • abundant capillaries
  • Accessory structures
    • hair & nail follicles, sensory receptors, glands
hair follicles
Hair Follicles
  • Made of epidermal tissue
  • Base of follicle (Fig. 5-3)
    • Hair root; mitosis occurs in matrix
      • Produce keratin
      • Get color from melanin
      • Die & become incorporated into hair shaft
      • Hair shaft pushed toward skin surface
hair follicles1
Hair Follicles
  • Eyelashes & eyebrows keep dust & sweat out of eyes
  • Nostril hairs keep dust from entering nasal cavities
  • Hair on head provides insulation
    • body hair doesn’t serve this purpose
  • Pilomotor (arrectorpili muscle) attached to each follicle
    • pull hair follicles upright (fear, cold)
nail follicles
Nail Follicles
  • On ends of fingers & toes
  • Produce nails; mitosis in nail root at the nail’s base (Fig. 5-4)
  • New cells produce keratin & die
  • Nail is dead keratin cells, but nail bed is alive
nails
Nails
  • Protect fingers & toes from mechanical injury
  • Allow dexterity
  • Good for scratching
receptors
Receptors
  • Cutaneous senses
    • touch, pressure, heat, cold, pain
  • Specific receptor for each sensation
  • Receptors & sensation provide CNS with information about external environment
glands
Glands
  • Made of epithelial tissue (Fig. 5-1)
  • Sebaceous glands
    • Secrete sebum (oil)
      • inhibits bacterial growth on skin’s surface
      • prevents drying of skin, hair
  • Ceruminous glands
    • in the dermis of ear canals
    • secrete cerumen (ear wax)
      • keeps outer surface of eardrum pliable; prevents drying
glands1
Glands
  • Sweat glands
    • 2 types
      • Apocrine – numerous in axillae (underarm), genital areas
      • Eccrine – numerous on forehead, upper lip, palms, soles
blood vessels
Blood Vessels
  • Capillaries in dermis
  • Arterioles
    • Smooth muscle in walls permits constriction or dilation
      • maintains body temp.
subcutaneous tissue
Subcutaneous Tissue
  • “superficial fascia”
  • Made of areolar and adipose tissue
  • Connects dermis to underlying muscles
  • Secondary line of defense
aging the integumentary system
Aging & The Integumentary System
  • Skin layers become thinner, more fragile
  • Fibroblasts die & are not replaced
  • Repair of breaks or cuts slows
  • Skin wrinkles
  • Glands become less active
  • Skin becomes dry
  • Temp. regulation becomes harder
  • Hair thins, turns white
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