also known as… the skin! epidermis pages 112-116
TRANSCRIPT
The Integumentary System
Also known as… The SKIN!
EPIDERMISPages 112-116
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Includes:◦ Skin (cutaneous membrane)◦ Skin derivatives/accessories:
Sweat glands Oil glands Hair Nails
Integumentary System
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Protection Regulates loss of body heat
◦ as controlled by the nervous system Aids in excretion of urea and uric acid Synthesizes vitamin D Sensory receptors detect:
◦ Touch ◦ Temperature◦ Pressure◦ Pain
Skin Functions
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Protects deeper tissues from:◦ Damage:
Mechanical damage (bumps) Chemical damage (acids and bases)
◦ Pathogens/microbial threats◦ Ultraviolet radiation (sunlight)◦ Thermal damage (heat or cold)◦ Desiccation (drying out)
Keratin protects the skin from water loss
How Skin PROTECTS
Table 4.1 Functions of the Integumentary System (1 of 2).
Table 4.1 Functions of the Integumentary System (2 of 2).
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Epidermis—top/outer layer◦ Stratified squamous epithelium◦ Keratinized (cornified- hardened by keratin) to
prevent water loss◦ Avascular◦ Most cells are keratinocytes
Dermis- lies below the epidermis◦ Dense connective tissue
Skin Structure
Figure 4.3 Skin structure.
Dermal papillae
Hair shaft
Pore
Appendages of skin• Eccrine sweat gland• Arrector pili muscle• Sebaceous (oil) gland• Hair follicle• Hair root
Cutaneous vascular plexus
Adipose tissue
Epidermis
Dermis
Papillarylayer
Reticularlayer
Hypodermis(subcutaneoustissue)
Nervous structures• Sensory nerve fiber• Lamellar corpuscle• Hair follicle receptor (root hair plexus)
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Hypodermis (subcutaneous tissue) lies underneath the dermis◦ Not technically part of the skin◦ Anchors skin to underlying organs◦ Composed mostly of adipose tissue◦ Functions:
shock absorberinsulates deeper tissues
Skin Structure
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composed of up to five layers avascular Most cells are keratinocytes
◦ Keratin is a fibrous protein that makes the epidermis tough
◦ Other cells include Melanocytes (make melanin) Sensory cells (Merkel cells) Immune cells (Langerhans cells- phagocytes)
Layers of the Epidermis
From bottom to top (deep to superficial)
Stratum Basale Stratum Spinosum Stratum Granulosum (Stratum Lucidum) –not always present Stratum Corneum
Layers of the Epidermis
Figure 4.4 The main structural features of the epidermis.
Desmosomes
Stratum corneum. Cells are dead;represented only by flatmembranous sacs filled withkeratin. Glycolipids in extracellularspace.
Stratum granulosum. Cells areflattened, organelles are deteriorating;cytoplasm full of granules.
Stratum spinosum. Cells containthick bundles of intermediatefilaments made of pre-keratin.
Stratum basale. Cells are activelydividing stem cells; some newlyformed cells become part of the moresuperficial layers.
Dermis
Keratinocytes
Epidermaldendritic cell
Merkelcell
Melanocytes Melaningranules
Sensorynerveending
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Also called stratum germinativum◦ Deepest layer of epidermis◦ Lies next to dermis ◦ Contains cells undergoing mitosis◦ Daughter cells are pushed upward to become the
more superficial layers
Stratum Basale
Several cell layers thick Contain bundles of intermediate filaments
that serve to resist tension House Langerhans cells
◦ your book calls these epidermal dendritic cells◦ Macrophages that help activate the immune
system◦ Star-shaped cells
Stratum spinosum
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thin; only 3-5 cell layers Cells are flat Thicker plasma membranes resist
destruction Contain granules that serve to:
◦ Form keratin in the upper layers◦ Produce waterproofing glycolipids; control water
loss
Stratum granulosum
Formed from dead cells of the deeper strata Occurs only in thick, hairless skin
◦ palms of hands◦ soles of feet
Stratum lucidum
Outermost (external and most superficial)layer of the epidermis◦ 20-30 cell layers thick
Shingle-like dead cells are completely filled with keratin◦ This protective protein prevents water loss from skin◦ Lysozomes consumed nuclei and organelles upon cell
death◦ This layer is called “cornified or horny” because the cells
are now called “corneocytes”
Stratum corneum
Figure 4.4 The main structural features of the epidermis.
Desmosomes
Stratum corneum. Cells are dead;represented only by flatmembranous sacs filled withkeratin. Glycolipids in extracellularspace.
Stratum granulosum. Cells areflattened, organelles are deteriorating;cytoplasm full of granules.
Stratum spinosum. Cells containthick bundles of intermediatefilaments made of pre-keratin.
Stratum basale. Cells are activelydividing stem cells; some newlyformed cells become part of the moresuperficial layers.
Dermis
Keratinocytes
Epidermaldendritic cell
Merkelcell
Melanocytes Melaningranules
Sensorynerveending
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A pigment (melanin) produced by melanocytes ◦ Found mostly in the stratum basale
Melanin accumulates in membrane-bound granules called melanosomes
Color produced is yellow to brown to black◦ More melanin = darker color
Amount of melanin depends upon:◦ Genetics◦ exposure to sunlight
Melanin
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Epidermal dendritic cells◦ Alert and activate immune cells to a threat from a
pathogen such as a bacterial or viral invasion
Merkel cells- sensory receptors◦ Serve as touch receptors called Merkel discs◦ Found at the epidermal-dermal boundary
Epidermal Dendritic Cells (Langerhans Cells) and Merkel Cells
Figure 4.4 The main structural features of the epidermis.
Desmosomes
Stratum corneum. Cells are dead;represented only by flatmembranous sacs filled withkeratin. Glycolipids in extracellularspace.
Stratum granulosum. Cells areflattened, organelles are deteriorating;cytoplasm full of granules.
Stratum spinosum. Cells containthick bundles of intermediatefilaments made of pre-keratin.
Stratum basale. Cells are activelydividing stem cells; some newlyformed cells become part of the moresuperficial layers.
Dermis
Keratinocytes
Epidermaldendritic cell
Merkelcell
Melanocytes Melaningranules
Sensorynerveending