The Integumentary System

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Chapter 4

• The Integumentary System

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Body Membranes
Figure 4.1

• Body membranes cover surfaces, line body cavities
  and forms protective sheets around organs
• Two groups
• Epithelial membranes
• Cutaneous, muscous and serous membranes
• Connective tissue membranes
• Synovial membranes

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Epithelial Membranes

• Covering and lining membranes
• Epithelial sheet covering an underlying
  connective tissue sheet
• Cutaneous membrane
• Skin
• Outer epithelial layer called epidermis
• Inner connective tissue layer called dermis

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Mucous Membrane

• Epithelial tissue can be a varied of types
  squamous, cuboidal, columnar
• Connective tissue lamina propria
• Lines cavities open to the exterior
• Respiratory, Urinary, Digestive, Reproductive
• Absorption and secretion
• May or may not secrete mucus

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Serous Membranes

• Simple squamous epithelium over areolar
  connective tissue
• Lines body cavities closed to the exterior
• In pairs
• Parietal layer covers the cavity
• Visceral layer covers the organ
• In-between the layers is serous fluid
• Pleural
• Pericardial
• Peritoneal

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Connective Tissue Membrane Figure 4.2

• Synovial membranes
• Areolar tissue layer (no epithelial tissue)
• Located in the capsule around joints
• Also line bursa sacs and tendon sheaths

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Integmentary System Figure 4.4

• Integument
• The skin - cutaneous membrane
• Characteristics
• Largest organ of body
• Two layers
• Epidermis
• Dermis
• Layer under the skin hypodermis /subcutaneous
  layer
• Accessory structures
• Hair, nails and glands

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Functions Table 4.1

• Protection from
• Mechanical damage
• Chemical damage
• Infection from bacterial damage
• From desiccation drying out
• From ultraviolet radiation damage from sunlight
• Thermal damage
• Temperature maintenance
• Heat loss or heat retention
• Production of Vit D
• Conversion of a modified cholesterol molecule to
  vit D by sunlight
• Aids in excretion of urea and uric acid

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• Sensory reception
• Cutaneous receptors
• Touch, pain, pressure, heat, cold

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Layers of Skin Figure 4.3

• Epidermis outer protective covering
• Stratified squamous (keratinized) epithelium
• Avascular
• Keratin hardened protein for protection and
  prevention of water loss
• Thick skin 5 layers
• Soles and palms
• Thin skin 4 layers
• Rest of the body (hairy areas)

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Epidermis

• Cells
• Keratinocytes mostly
• Mitotic in the deepest layer (near dermal blood
  supply)
• Pushed up by production of new cells underneath
• Manufacture keratin fibrous protein
• Eventually fills cell pushing out nucleus and
  organelles
• Protects and waterproofs

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Layers of Epidermis Strata Figure 4.3

• Germinativum/Basale deepest layer
• Contains keratinocytes mitotic cells
• Forms epidermal ridges extending into dermis
  forming dermal papilla responsible for
  fingerprints
• Also contains melanocytes produce pigment
  melanin
• Stratum Spinosum spiny layer
• Spiny layer/mitotic
• Stratum Granulosum grainy layer
• Manufacture keratin granules
• Stratum Lucidum clear layer
• Cells filled with keratin only in thick skin

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• Stratum Corneum
• Most superficial layer
• Thickest layer, 10 30 cell layers
• Cells are completely dead and filled with keratin
• Completely replaced every 2 4 weeks

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Dermis

• Dense fibrous connective tissue
• Vascular
• Two layers
• Papillary
• Upper 20
• Areolar connective tissue
• Reticular
• Lower 80
• Dense fibrous connective tissue some adipose
  tissue
• Thicker in palms and soles
• Thin in eyelids

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Fibers

• Collagen fibers
• Toughness of dermis
• Bind to water and keep skin hydrated
• Elastic fibers
• Elasticity to skin
• Aging process
• Fibers decrease
• Subcutaneous layer loses fat
• Skin sags and wrinkles develop

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Papillary Layer

• Contains dermal papillae
• Location
• Finger-like projections into dermis
• Appearance
• Contain capillaries which nourish epidermis
• Contain free nerve endings for pain
• Contain Meissners corpuscle touch
• Collagen and elastic fibers
• Palms and soles
• Increased friction and gripping ability
• Helps form finger/foot prints

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Reticular Layer

• Location
• Deep to papillary layer
• Appearance
• Collagen fibers
• Elastic fibers
• Contains Pacinian corpuscles
• Deep pressure receptors
• Contains glands sweat and oil
• Contains blood vessels

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Subcutaneous Layer Hypodermis

• Subcutaneous tissue / Superficial fascia
• Under skin not part of skin
• Connective tissue mostly adipose
• Functions
• Cushioning, insulation, reserve energy supply
• Anchors skin to underlying structures
• Forms the curves of the body
• Thickens during weight gain
• Contains no vital organs and few blood vessels
• Used for subcutaneous injection of drugs

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Skin Color

• Carotene pigment
• Source
• Orange/yellow vegetables (carrots, squash)
• Appearance
• Orange/yellow pigment
• More intense as more orange/yellow vegetables are
  eaten
• Converted to Vitamin A for maintenance of
  epithelial tissue and night vision
• Location
• Accumulated in stratum corneum
• Most visible in palms and soles

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Melanocytes

• Melanin pigment
• Source
• From melanocytes only skin pigment produced by
  the skin
• Appearance
• Brown to black pigment
• Location
• Produced in stratum basale and granules are
  transferred to the keratinocytes
• Granules form an arc over the nucleus protecting
  it from ultraviolet rays

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• All humans have the same relative number of
  melanocytes
• Differences in color is due to differences in
  melanocyte activity
• Freckles and moles
• Melanin activity concentrated in one spot
• Tan
• Sunlight increasing melanocyte activity

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Blood Vessels

• Located in the dermis
• Arteries red transport oxygen and nutrients
• Veins - blue remove waste products
• Blood vessels maintain body temperature
  homeostasis
• Increase in temperature
• Causes blood vessels to dilate releasing heat
  from the body
• Skin reddens, becomes warm, gives off heat
• Decrease in temperature
• Causes blood vessels to constrict holding heat in
  the core of the body to protect vital organs
• Skin takes on a bluish color - Frostbite

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Hemoglobin

• Pink pigment in red blood cells
• Transports oxygen and carbon dioxide
• More evident in people with less melanin
• Dilated blood vessels
• Skin has a red tone
• Constricted blood vessels
• Skin is pale
• Cyanosis

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Cutaneous Glands
Figure 4.6

• Exocrine glands ducted
• Release secretions to skin surface
• Sebaceous glands Oil glands
• Location
• All over body except palms and soles
• Ducts empty to hair follicle
• Appearance
• Glands which secrete oil (sebum), a lipid

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• Function
• Contraction of arrector pili muscle squeezes the
  gland forcing the sebum out
• Sebum lubricates hair and skin
• Inhibits growth of bacteria
• Sensitive to changes in concentration of sex
  hormones secretion increases during puberty
• Holocrine glands
• Cells rupture during secretion - Cell fragments
  and sebum
• Excesses Acne
• Ducts are blocked with cell fragments

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Sudoriferous Glands (Sweat Glands) Figure 4.6

• Apocrine Glands
• Location
• Axial and anogenital areas connecting to hair
  follicles
• In various places in the dermis ducted to skin
  surface
• Appearance
• Large, coiled glandular structure with duct
• Secretion
• Sticky, cloudy secretion
• Becomes odorous when broken down by bacteria
• Antiperspirants contain astringents which
  contract the skin and sweat gland openings
  decreasing quantity of secretions

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Merocrine/Eccrine Glands

• Location
• More numerous and widely distributed
• Most in palms and soles
• Appearance
• Coled tubular glands with ducts
• Secretion
• 99 water
• 1 sodium chloride, organic nutrients, wastes
  urea (odoriferous)
• Acidic kills bacteria
• Function
• Secretion called perspiration
• Cools surface of skin reducing body temperature

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Accessory Structures - Hair
Figure 4.7 4.8

• Location
• All over the body except palms, soles, lips,
  nipples, portions of external genitals
• Non-living structure
• Hair Regions
• Shaft superficial to epidermis
• Root in epidermis and dermis
• Hair follicle
• Produces the hair
• Contains all the cell layers of epidermis except
  corneum
• Hair papilla
• Base of hair follicle containing nerves, blood
  vessels
• Area of hair growth

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Modified Sudoriferous Glands

• Ceruminous glands
• Located in external ear
• Secretion is called cerumen (ear wax)
• Repels insects, traps foreign particles,
  antiseptic
• Mammary glands
• Functional in female breast
• Secretion is milk

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Regions of Hair

• Hair bulb
• Wide area at base of hair root
• Contains the hair papilla
• Hair growth cycle
• Scalp
• Grows 2 5 years about .3 mm/day
• Inactive the same amount of time
• New growth period and the old hair is pushed out
• Different rates in different follicles

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Functions of Hair

• Scalp hairs
• Protect from ultraviolet light
• Cushion head
• Insulate head
• Hair in nasal cavity and ear canals and eyelashes
• Prevent entry of foreign particles and insects
• Each hair has a sensory nerve fiber
• Early warning sign

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Arrector Pili Muscle

• Location
• Extends from papillary dermis to hair follicle
• Appearance
• Smooth muscle
• Function
• Contracts and pulls hair up
• Response to cold, fear, rage
• Goose bumps

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Hair Color

• Differences in the type and amount of pigment
  produced by melanocytes at the papilla
• Dark brown, yellow brown, red
• Pigment production decreases with age hair
  lightens
• White hair
• Lack of pigment and air bubbles in hair shaft

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OMIT

• No Nails
• No Homeostatic Imbalance