C H A P T E R

Copyright © 2010 Pearson Education, Inc.

5

The Integumentary System

Skin (Integument)

• Consists of three major regions

1. Epidermis—superficial region

2. Dermis—middle region

3. Hypodermis (superficial fascia)—deepest region

• Subcutaneous layer deep to skin (not technically part of skin)

• Mostly adipose tissue

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Figure 5.1

Epidermis

Hair shaft

Dermis Reticularlayer

Papillarylayer

Hypodermis(superficial fascia)

Dermal papillae

Pore

Subpapillaryvascular plexus

Appendagesof skin • Eccrine sweat gland• Arrector pili muscle• Sebaceous (oil) gland• Hair follicle• Hair rootNervous structures

• Sensory nerve fiber• Pacinian corpuscle• Hair follicle receptor (root hair plexus)

Cutaneous vascularplexus

Adipose tissue

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Epidermis

• Keratinized stratified squamous epithelium

• Cells of epidermis

• Keratinocytes—

• Melanocytes---

• Epidermal dendritic (Langerhans) cells—

• Tactile (Merkel) cells —

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Figure 5.2a

Dermis

Stratum corneumMost superficial layer; 20–30 layers of deadcells represented only by flat membranoussacs filled with keratin. Glycolipids inextracellular space.Stratum granulosumThree to five layers of flattened cells,organelles deteriorating; cytoplasm full oflamellated granules (release lipids) andkeratohyaline granules.Stratum spinosumSeveral layers of keratinocytes unified bydesmosomes. Cells contain thick bundles ofintermediate filaments made of pre-keratin.Stratum basaleDeepest epidermal layer; one row of activelymitotic stem cells; some newly formed cellsbecome part of the more superficial layers.See occasional melanocytes and epidermaldendritic cells.

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Layers of the Epidermis: Stratum Basale (Basal Layer)

• Deepest epidermal layer firmly attached to the dermis

• Single row of stem cells

• Also called stratum germinativum: cells undergo rapid division

• Journey from basal layer to surface

• Takes 25–45 days

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Layers of the Epidermis: Stratum Spinosum (Prickly Layer)

• Cells contain a weblike system of intermediate prekeratin filaments attached to desmosomes

• Abundant melanin granules and dendritic cells

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Layers of the Epidermis: Stratum Granulosum (Granular Layer)

• Thin; three to five cell layers in which the cells flatten

• Keratohyaline and lamellated granules accumulate

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Layers of the Epidermis: Stratum Lucidum (Clear Layer)

• In thick skin

• Thin, transparent band superficial to the stratum granulosum

• A few rows of flat, dead keratinocytes

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Layers of the Epidermis: Stratum Corneum (Horny Layer)

• 20–30 rows of dead, flat, keratinized membranous sacs

• Three-quarters of the epidermal thickness

• Functions

• Protects from abrasion and penetration

• Waterproofs

• Barrier against biological, chemical, and physical assaults

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Figure 5.2b

MelanocyteMelanin granule

Tactile(Merkel) cell

Sensorynerve ending Epidermal

dendritic cell

Dermis

KeratinocytesStratum corneumMost superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space.Stratum granulosumThree to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules.Stratum spinosumSeveral layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin.Stratum basaleDeepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and epidermal dendritic cells. Desmosomes

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Dermis

• Strong, flexible connective tissue

• Cells include -

• Two layers:

• Papillary

• Reticular

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Figure 5.1

Epidermis

Hair shaft

Dermis Reticularlayer

Papillarylayer

Hypodermis(superficial fascia)

Dermal papillae

Pore

Subpapillaryvascular plexus

Appendagesof skin • Eccrine sweat gland• Arrector pili muscle• Sebaceous (oil) gland• Hair follicle• Hair rootNervous structures

• Sensory nerve fiber• Pacinian corpuscle• Hair follicle receptor (root hair plexus)

Cutaneous vascularplexus

Adipose tissue

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Hypodermis

• Subcutaneous layer deep to the skin

• Composed of adipose and areolar connective tissue

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15

Synovial Joints

• Those joints in which the articulating bones are separated by a fluid-containing joint cavity

• All are freely movable joint _ diarthroses

• Examples – all limb joints, and most joints of the body

16

Synovial Joints: General Structure

• Synovial joints all have the following

• Articular cartilage

• Joint (synovial) cavity

• Articular capsule

• Synovial fluid

• Reinforcing ligaments

17

Synovial Joints: General Structure

Figure 8.3a, b

18

Synovial Joints: Friction-Reducing Structures

• Bursae – flattened, fibrous sacs lined with synovial membranes and containing synovial fluid

• Common where ligaments, muscles, skin, tendons, or bones rub together

• Tendon sheath – elongated bursa that wraps completely around a tendon

19

Synovial Joints: Friction-Reducing Structures

Figure 8.4

20

Synovial Joints: Stability

• Stability is determined by:

• Articular surfaces – shape determines what movements are possible

• Ligaments – unite bones and prevent excessive or undesirable motion

• Muscle tone is accomplished by:

• Muscle tendons across joints acting as stabilizing factors

• Tendons that are kept tight at all times by muscle tone

21

Synovial Joints: Movement

• The two muscle attachments across a joint are:

• Origin – attachment to the immovable bone

• Insertion – attachment to the movable bone

• Described as movement along transverse, frontal, or sagittal planes