chapter 6 skin and the integumentary system n.
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Chapter 6: Skin and the Integumentary System - PowerPoint PPT Presentation

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Chapter 6: Skin and the Integumentary System. Skin: Largest organ Otherwise known as cutaneous membrane Forms barrier between our internal environment and the external world Vital in maintaining homeostasis Regulates body temperature Prevents water loss Houses sensory receptors

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    • Largest organ
    • Otherwise known as cutaneous membrane
    • Forms barrier between our internal environment and the external world
    • Vital in maintaining homeostasis
      • Regulates body temperature
      • Prevents water loss
      • Houses sensory receptors
      • Synthesize biochemicals
      • Excretes wastes (very small amount)
  • Makes up integumentary system
    • Includes skin and accessory organs

Two layers:

    • 1) Epidermis:
      • Outer layer
      • Composed of stratified squamous epithelial tissue
    • 2) Dermis
      • Inner layer
      • Contains:
        • Connective tissues (collagenous fibers, elastic fibers, blood)
        • Epithelial tissue
        • Smooth muscle tissue
        • Nervous tissue

Other layers:

    • 1) Basement:
      • Anchors dermis to epidermis
    • 2) Hypodermis or Subcutaneous:
      • Beneath skin
      • Contains masses of loose connective and adipose tissue
      • Binds skin to underlying organs


    • Lacks blood vessels
    • Composed of stratified squamous epithelium tissue
    • Divides and grow
      • Pushes older cells away from dermis and towards surface
      • Become less and less nourished and eventually die
      • Keratinization: older cells harden and die (cytoplasm fills with keratin protein)
      • Healthy skin: balances cell division with cell death
      • Areas of continual wear: causes fast cell division and thickened layers called calluses (hands, soles of feet) and corns (toes)

Layers of epidermis:

    • Stratum corneum:
      • Hardened outer layer (mostly dead, keratinized cells)
    • Stratum lucidum:
      • Only present in palms and soles of feet
      • Hardened, thickened layer
    • Stratum granulosum:
      • Very thin layer
    • Stratum spinosum:
      • More spacious, numerous
    • Stratum basale:
      • Nourished by blood vessels in dermis, newest cells, most nourished, next to basement membrane

Characteristics, cont.:

    • Important protective functions
      • Shields moist underlying tissues against:
        • Excessive water loss
        • Mechanical injury
        • Effects of chemicals, mutagens, pollutants
        • Pathogens
    • Contains melanocytes (cells which produces melanin – dark pigment that provides skin color to protect against UV)
      • Albinism: inability to produce melanin
epidermis skin color

Largelydue to amount of melanin

  • All people have the same average number of melanocytes
    • Differences in color: come from the AMOUNT of melanin the melanocytes produce
    • Most genetically determined
    • Environmental effects: UV (sun and artificial), X-rays
    • Physiological effects: blood in dermal layer
      • Red: well-oxygenated;
      • Blue (very dark red)-deoxygenated
        • Called cyanosis
      • Yellow (diet) – yellow vegetables containing B-carotene
Epidermis: Skin Color


    • Contain dermal papillae (projections of the dermis which extend into epidermal spaces)
      • Fingerprints are as a result of these projections (determined by genes)
    • Binds epidermis to underlying tissues
    • Composed of dense connective tissue (includes collagenous and elastic fibers)
    • Contains blood vessels (supply nutrients to all skin cells, regulate body temperature)
    • Nerve cells scattered throughout
    • Contain hair follicles, sebaceous glands, sweat glands
subcutaneous layer


    • Otherwise known as hypodermis
    • Contains loose connective and adipose tissues
    • Composed of collagenous and elastic fibers (continuous with those of dermis)
    • No sharp boundary between this layer and dermis
    • Adipose:
      • Insulates
      • Regulates body temp (conserving body heat, not allowing heat to enter)
    • Contains blood vessels
Subcutaneous Layer


    • Protective coverings
    • Consists of nail plate (overlies surface of the skin called the nail bed)
    • White, base of nail (lunula) – covers the most actively growing portion of epidermis
    • As cells divide here, they keratinize
    • Then these keratinized cells become scales that become part of nail plate
      • Thumb: slowest
      • Middle: fastest
hair follicles


    • Present everywhere BUT palms, soles, nipples
    • Hair develops from group of epidermal cells at the base of hair follicle
    • Follicle extends from surface into dermis
    • Cells nourished via dermal blood vessels
    • As cells grow and divide, pushed upward
    • As push upward, keratinize and die
Hair Follicles
hair follicles1


    • Remains become structure of hair (shaft extends outward)
    • Color: determined by genes (direct color and amount of pigment)
    • Arrectorpili muscle – smooth muscle, attach to each hair follicle
      • These muscles can be stimulated to contract (when heat is needed) – produces gooseflesh (goosebumps)
Hair Follicles
sebaceous glands


    • Otherwise known as oil glands
    • Closely associated with hair follicles
    • Holocrine glands (secrete oily mixture of fatty and sebum – cellular wastes)
      • Secrete mixture through small ducts
      • Sebum – helps keep hair and skin soft, pliable and waterproof
Sebaceous glands
sweat glands


    • Otherwise known as sudoriferous glands
    • Exocrine gland
    • Widespread
    • Consists of:
      • Tiny coiled tube laying in subcutaneous layer or deep dermal layer
    • Most numerous type: eccrine (respond to body temperature changes)
    • Common forehead, neck and back (produce profuse sweat)
Sweat glands
sweat glands1


    • Sweat (fluid) carried away via duct which leads to pore (on surface)
      • Sweat is mostly water
      • Contains small amount of salt, wastes (urea, uric acid)
    • Apocrine glands:
      • Become active at puberty
      • Secrete via same mechanism as eccrine glands
      • Secrete when person is emotionally upset, frightened or in pain
      • Most numerous in groin and axillary region
    • Mammary glands:
      • Modified sweat glands, secrete milk
Sweat glands
regulate body temperature

Humans: Internal temp = 98.6oF (37oC)

  • Mammals must balance heat gained with heat lost
  • Skin plays vital role in maintaining this homeostatic mechanism
  • As body temp drops, nerve impulses stimulate structures in skin to conserve heat
    • Blood vessels contract, decreasing flow (reduces heat loss)
    • Sweat glands are inactive
    • Muscle contract – producing heat
Regulate body temperature
regulate body temperature1

As body temp rises, nerve impulses stimulate structures in skin to release heat

    • Blood dilation (more blood enter, heat carries/escapes)
    • Warm blood reaches hypothalamus (which controls body temperature set point)
    • Eccrine sweat glands release sweat (as sweat evaporates, heat is carried away from surface)
  • Hot vs. Cold
Regulate body temperature
healing wounds

Inflammatory response:

    • Normal response to injury or stress
    • Red, painful, warm, swollen
      • Becomes red when blood vessels dilate and become more permeable (forces fluids to leave vessels and enter tissue)
      • Advantage: Provides tissue with more nutrients and oxygen (aid in healing process)
Healing Wounds
healing wounds1

Shallow cut

    • Epithelium will divide rapidly, filling in gap
  • Deep cut
    • Blood vessels break, clot forms
    • Clot and tissues form scab (protect underlying tissues)
    • Fibroblasts migrate to injury and begin forming new collagenous fibers (bind edges of wound together)
    • Scar: forms when connective tissue appears on surface
Healing Wounds