c h a p t e r copyright © 2010 pearson education, inc. 5 the integumentary system
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C H A P T E R
Copyright © 2010 Pearson Education, Inc.
5
The Integumentary System
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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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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
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Synovial Joints: General Structure
• Synovial joints all have the following
• Articular cartilage
• Joint (synovial) cavity
• Articular capsule
• Synovial fluid
• Reinforcing ligaments
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Synovial Joints: General Structure
Figure 8.3a, b
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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
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Synovial Joints: Friction-Reducing Structures
Figure 8.4
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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
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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