Integumentary System

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CHAPTER 6
Integumentary System
• Dermatology – scientific study and medical treatment of the integumentary system. • Integumentary System – consists of the skin and its accessory organs – hair, nails, and cutaneous glands
• skin is the most vulnerable organ
• skin is the most vulnerable organ
– exposed to radiation, trauma, infection, and injurious chemicals • body’s largest and heaviest organ

Skin and Subcutaneous Tissue
• consists of two layers:
– epidermis – stratified squamous epithelium
– dermis – connective tissue layer
– hypodermis
• another connective tissue layer below the dermis
• not part of the skin
• contains fat tissue (for insulation), blood vessels and nerves

• thick skin
– on palms and sole, and corresponding surfaces on fingers and toes – has sweat glands, but no hair follicles or sebaceous (oil) glands • thin skin
– covers rest of the body
– possesses hair follicles, sebaceous glands and sweat glands

Functions of the Skin
• resistance to trauma and infection
– keratin (mechanical protection)
– acid mantle (prevents bacterial from entering body)
- macrophages –“reach out and touching each other to detect bacteria” • other barrier functions
– waterproofing
- resists dehydration
– UV radiation
– harmful chemicals
• vitamin D synthesis
– skin is first step of synthesis
– liver and kidneys complete process
• sensation
– skin is our most extensive sense organ
• thermoregulation
– thermoreceptors
– vasoconstriction (when cold)/ vasodilation (when hot)
• transdermal absorption
– administration of certain drugs steadily through thin skin

Structure of the Skin

Cell Types and Layers of the of the Epidermis

Hair Follicle
Hair Follicle

Epidermis
• keratinized stratified squamous epithelium
– dead cells at the surface packed with tough protein – keratin – lacks blood vessels
– depends on the diffusion of nutrients from underlying connective tissue -dermis – contains nerve endings for touch and pain

Five Types of Cells of the Epidermis
– stem cells
• undifferentiated cells that give rise to keratinocytes
• in deepest layer of epidermis (stratum basale)
– keratinocytes (stratified squamous epithelial cells)
• great majority of epidermal cells
• synthesize keratin
“As keratinocytes mature and move further away from the basal skin they are dying. Their cytoplasm and organelles are being replaced by the protein called keratin. Will become dead shells filled with keratin.” – melanocytes

• occur only in stratum basale
• synthesize pigment melanin through secretion vesicles that shields DNA from ultraviolet radiation (protection) “Melanin will accumulate above the nucleus of the cell for protection” • branched processes spread melanin among keratinocytes

– tactile (merkel) cells
• in basal layer of epidermis
• touch receptor cells associated with dermal nerve fibers - merkel disk- ends like a cup – attributes to sensation along with merkel cell “if someone touches your skin and compresses your cells into your merkle disks that allows us the sensation of being touched” – dendritic (langerhans) cells

• macrophages originating in bone marrow (originate from blood tissue) that guard against pathogens • found in stratum spinosum and granulosum
• stand guard against toxins, microbes, and other pathogens that penetrate skin “Their processes stretch out and touch each other’s prcesses creating a net through our entire skin that nothing can penetrate without being detected. It will either attack the pathogen or call out bigger troops”

• thick skin
– 5 layers of skin (extra layer- stratum lucidum)
– on palms and sole, and corresponding surfaces on fingers and toes – has sweat glands, but no hair follicles or sebaceous (oil) glands • thin skin
- 4 layers of skin
– covers rest of the body
– possesses hair follicles, sebaceous glands and sweat glands

Stratum Basale
“lowest layer/ mitotic layer”
• a single layer of cuboidal to low columnar stem...
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