BIO 210 Lab

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Chapter 5The Integumentary System

• BIO 210 Lab
• Instructor Dr. Rebecca Clarke

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Parts of the Integumentary System

• Cutaneous membrane (integument, skin)
• (outer) epidermis superficial epithelium
• (inner) dermis underlying area of connective
  tissues
• Accessory structures located primarily in
  dermis, protrude through epidermis to skin
  surface
• Hair
• Nails
• (Multicellular) exocrine glands
• Also
• Blood vessels throughout dermis
• Sensory receptors monitor touch, pressure,
  temperature, pain

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Integumentary System

• Cutaneous membrane epidermis dermis

Figure 51
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Layers (Strata) of Epidermis

• From basal lamina to free surface
• stratum germinativum
• stratum spinosum
• stratum granulosum
• stratum lucidum
• stratum corneum

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Stratum Germinativum (Basale)

• Single layer of basal (germinative, stem) cells
• Site of cell division replenishes epidermis
• Attached to basal lamina by hemidesmosomes
• Forms strong bond between epidermis and dermis

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Stratum Germinativum

• Forms epidermal ridges (Fig 5-2)
• fingerlike projections into dermis underneath
  intermesh with dermal papillae
• ? ridge-shaped pattern (fingerprint) on surface
  of skin which is unique for each individual
  (genetically determined) (Fig 5-4)
• increase strength and bond between epidermis and
  dermis
• Has melanocytes (with melanin pigment) give
  skin its color (Fig 5-5)

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Organization of the Epidermis
Figure 52
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Ridges and Ducts
Figure 54
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Stratum Spinosum

• Spiny layer
• cells shrink until cytoskeletons stick out
  (spiny)
• 8-10 cell layers of keratinocytes
• Dividing cells from stratum germinativum push up
  through this layer
• Still some cell division

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Stratum Granulosum

• Grainy layer
• 3-5 cell layers thick
• Cells stop dividing, start producing proteins ?
  grainy appearance
• keratin
• tough, fibrous protein
• makes up hair and nails
• ? water resistant, not waterproof
• keratohyalin
• dense granules
• cross-link keratin fibers
• ? tightly interlocked cell layers
• Cells
• thinner, flatter, less permeable
• further from papillary plexus, start to die

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Stratum Lucidum

• Clear layer
• Cells flattened, densely packed, filled with
  keratin ? barrier to water
• Only in thick skin (on palms and soles)

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Stratum Corneum

• Horn/hard layer on exposed surface of skin
• 15-30 cell layers of dead cells (far from
  nutrients in dermis) durable, expendable ?
  protective function
• Cells filled with keratin ( keratinized) ?
  water-resistance (not waterproof)
• Cells tightly interconnected by desmosomes so are
  sloughed off in sheets
• Cells remain for 2 weeks (total of 6 weeks from
  origin in stratum germinativum to sloughing)

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2 Kinds of Skin

• Thin skin
• Has 4 layers of keratinocytes (missing stratum
  lucidum)
• Covers most of body
• Thick skin
• Has all 5 layers of keratinocytes
• Covers heavily abraded body surfaces, e.g., palms
  of hands, soles of feet

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Dermis

• Located between epidermis and subcutaneous layer
• Contains
• Blood and lymph vessels
• Nerve fibers and sensory receptors
• Tactile (Meissners) corpuscles sensitive to
  light touch located in dermal papilla
• Lamellated (Pacinian) corpuscles sensitive to
  deep pressure and vibration
• Accessory organs (of epidermal origin), e.g.,
  hair follicles, sweat glands

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Components of Dermis

• 2 major components boundaries indistinct
• Papillary layer
• Reticular layer
• Associated structures
• Papillary plexus branching network of small
  arteries in papillary layer of dermis which
  provide blood to capillary loops that follow
  contours of epidermis-dermis boundary

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Papillary Layer

• Has dermal papillae projecting between epidermal
  ridges
• Consists of areolar tissue
• Contains smaller capillaries, lymphatics, and
  sensory neurons

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Reticular Layer

• Deep to papillary layer
• Consists of dense irregular connective tissue
• Contains
• Larger blood vessels, lymph vessels, and nerve
  fibers
• Collagen and elastic fibers ?
• Strength and elasticity
• Flexibility

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Dermatitis

• An inflammation of the papillary layer
• Caused by infection, radiation, mechanical
  irritation, or chemicals (e.g., poison ivy)
• Characterized by itch or pain

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Subcutaneous Layer

• aka hypodermis (below dermis), superficial
  fascia
• Highly vascularized contains large arteries and
  veins site of subcu injections
• Separates integument from deep fascia around
  other organs, e.g., muscles and bones
• Stabilizes position of skin relative to
  underlying tissues, e.g., skeletal muscles or
  other organs, while permitting independent
  movement

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Structure of Subcutaneous Layer

• Consists of
• Elastic areolar (loose) connective tissue
• Adipose tissue (energy reserve, shock absorber)

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Accessory Structures of the Integumentary System

• Derived from epidermis
• Located in dermis
• Extend through epidermis to skin surface
• Include
• Hair follicles and hairs
• Exocrine glands
• Nails

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Structure of a Hair and Follicle
Figure 510a
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Hair Follicles

• Living organs
• Produce nonliving hairs complex process
  involving dermis and epidermis
• Extend deep into/through dermis and into
  underlying subcutaneous layer
• Wrapped in dense connective tissue sheath of
  dermis

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Follicle Wall

• Composed of epithelial cells
• Cells organized into 3 concentric layers (from
  outside in)
• Glassy membrane
• Thickened basal lamina
• External root sheath
• Widest layer
• Internal root sheath
• Contacts cuticle (outer layer of hair)

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Structure of a Hair and Follicle
Figure 510
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Structure of a Hair Follicle

• Hair bulb
• Bulbous mass of epithelial cells
• Hair matrix
• Layer of epithelial cells in central, deepest
  part of follicle
• Site where cell division begins that produces
  hair
• Cells gradually pushed toward surface as hair
  gets longer
• Hair papilla
• At base of follicle (below matrix)
• Peg of connective tissue that contains
  capillaries and nerves
• If damaged, hair will not grow

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Structure of a Hair and Follicle
Figure 510
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Hair Structure

• Hair root
• Lower part of hair
• Begins at base of hair (bulb) and extends about
  halfway to skin surface
• Anchors hair into skin
• Hair shaft
• Upper part of hair
• Extends from above the root to above the skin
  surface

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Structure of a Hair and Follicle
Figure 510
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Layers Within Hair

• Cuticle
• Outer surface
• Layer of overlapping, dead keratinized cells
• Contains hard keratin ? hair stiffness
• Cortex
• Intermediate layer below cuticle
• Also contains hard keratin
• Medulla
• Middle layer, central core
• Contains soft keratin
• Flexible

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Structure of a Hair and Follicle
Figure 510
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Associated Structures

• Arrector pili muscle
• Involuntary smooth muscle
• Contractions cause hairs to stand up ? goose
  bumps

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Exocrine Glands

• Sebaceous (oil) glands
• holocrine glands
• secrete sebum
• Sweat (sudoriferous) glands
• merocrine glands
• apocrine glands

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Types of Sweat Glands

• Apocrine
• Associated with hair follicles
• Found in armpits, around nipples, and groin
• Merocrine
• Widely distributed on body surface
• Especially on palms and soles

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Merocrine Sweat Glands

• Also called eccrine glands
• Smaller but more numerous
• Coiled, tubular glands
• Watery secretion sensible perspiration
  (produced by glands) vs. insensible perspiration
  which is the loss of fluid by evaporation through
  the stratum corneum

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Nails

• Nonliving structures made of dead cells packed
  with keratin
• Form on dorsal surface of tips of fingers and
  toes
• Function protect fingers and toes
• Metabolic disorders can change nail structure,
  e.g., shape, appearance can assist in diagnosis

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Nail Structure

• Nail body - Superficial, visible portion
• Nail bed area of epidermis under nail body
• Nail root epidermal fold not visible from
  surface where nail production occurs
• Eponychium extends over exposed nail forming
  cuticle
• Hyponychium skin beneath free edge of nail
• Lunula (moons) pale crescent at base of nail
  where underlying blood vessels may be obscured

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Structure of a Nail
Figure 513