Integumentary System

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Integumentary System

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Integumentary System

• Epidermis (epithelial tissue)
• Dermis (connective tissue)
• Hypodermis (not part of the skin)

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Hypodermis

• subcutaneous layer (underneath the skin)

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Hypodermis

• contains areolar and adipose tissue

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Hypodermis

• attaches skin to underlying tissues and organs

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Hypodermis

• Conatains pacinian corpuscles ( sensitive to
  pressure / looks like an onion)

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Epidermis

• Stratified Squamous epithelium
• 4 different types of cells
• 5 layers

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Types of Cells in Epidermis

1. Keratinocytes
2. Melanocytes
3. Langerhans
4. Merkel

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Keratinocytes

• 90 of epidermal cells

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Keratinocytes

• produce the protein keratin which protects the
  skin and underlying tissues from heat, microbes,
  and chemicals

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Keratinocytes

• produce lamellar granules which produce a water
  repellant sealant

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Melanocytes

• 8 of epidermal cells

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Melanocytes

• Produces the pigment melanin

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Melanocytes

• Transfers melanin granules to keratinocytes

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Melanocytes

• In keratinocytes the melanin granules acts like
  an umbrella over the DNA in order to protect it
  from UV light

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Langerhans

• migrate from red bone marrow to epidermis

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Langerhans

• involved in immune response

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Merkel

• sensitive to touch

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Merkel

• located in stratum basale

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Merkel

• Have contact with the flattened process of a
  sensory neuron (Merkel disc)

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5 layers of Epidermis

1. Stratum Basale
2. Stratum Spinosum
3. Stratum Granulosum
4. Stratum Lucidum
5. Stratum Corneum

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Stratum Basale

• Deepest layer of the epidermis

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Stratum Basale

• Single layer of cuboidal or columnar
  keratinocytes

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Stratum Basale

• Nuclei large

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Stratum Basale

• Also contains some melanocytes, merkel cells, and
  langerhans cells

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Stratum Spinosum

• 8 to 10 layers of squamous shaped keratinocytes

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Stratum Spinosum

• Has a large nucleus

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Stratum Spinosum

• Appear spiny underneath microscope

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Stratum Spinosum

• Some langerhans cells and melanocytes

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Stratum Granulosum

• 3 to five layer of squamous keratinocytes

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Stratum Granulosum

• Undergoing apoptosis (cell death)

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Stratum Granulosum

• Nuclei disappearing

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Stratum Granulosum

• Contains protein keratohyalin which converts
  tonofilaments into keratin

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Stratum Granulosum

• Secretes lamellar granules which fills the spaces
  between stratum granulousum, stratum lucidum, and
  stratum corneum

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Stratum Lucidum

• Only in thick skin

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Stratum Lucidum

• 3 to 5 layers of clear, dead, squamous
  keratinocytes

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Stratum Lucidum

• Contain keratin

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Stratum Corneum

• 25 to 30 layers

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Stratum Corneum

• Dead squamous keratinocytes

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Stratum Corneum

• Contain keratin

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Stratum Corneum

• Sometimes forms callus (the stratum corneum is
  abnormally thick)

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Dermis

• Two Regions
• Papillary Region
• Reticular Region

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Papillary Region

• Contains areolar connective tissue with fine
  elastic fibers

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Papillary Region

• 20 percent or one fifth of dermis

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Papillary Region

• Contains Meisner corpuscles ( sensitive to
  touch)

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Papillary Region

• Contains dermal papillae (small,fingerlike
  projections that indent the epidermis and some
  contain capillary loops)

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Reticular Region

• Contains dense irregular connective tissue with
  collagen fibers and course elastic fibers

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Reticular Region

• Contain some adipocytes, hair follicles,
  nerves, sebaceous glands, and sweat glands

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Skin Color

• Melanin
• Carotene
• Hemoglobin

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Melanin

• Number of melanocytes doesnt vary among people

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Melanin

• Differences in skin color can be attributed to
  the amount that these melanocytes produce

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Melanin

• Melanocytes most commonly found in the epidermis
  of the penis, nipples, face and limbs

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Melanin

• Freckles and age spot (accumulations of melanin)

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Carotene

• Yellow-orange pigment
• Precursor to vitamin A

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Carotene

• Found in stratum corneum, fatty areas of dermis,
  and hypodermis

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Hemoglobin

• Protein in rbcs that carries oxygen
• Found in capillaries in blood

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Albinos

• Contain melanocytes, but are unable to produce
  melanin
• Inherited
• Melanin is absent in hair, eyes, and skin

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Vitiligo

• Irregular white spots
• Due to loss of melanocytes
• Antibodies in body attack melanocytes

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Types of Skin

1. Thin Skin
2. Thick Skin

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Thin Skin

• Covers all surfaces except palms, fingertips,
  and soles

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Thin Skin

• Lacks stratum lucidum
• Thin stratum spinosum and corneum

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Thin Skin

• Lack epidermal ridges (fingerprints)

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Thin Skin

• Fewer sweat glands
• Fewer sensory receptors

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Thin Skin

• Contains hair follicles, arrector pili muscles,
  and sebaceous (oil) gland

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Thick Skin

• Located on palms, fingertips, and soles

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Thick Skin

• Stratum Lucidum
• Thicker stratum spinosum and corneum

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Thick Skin

• Contains epidermal ridges
• Contains more sweat glands

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Thick Skin

• Lacks hair follicles, sebaceous glands, and
  arector pili muscles

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Accessory Structures

1. Hair
2. Glands
3. Nails

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Hair

• Shaft
• Superficial portion of hair

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Hair

• Root
• Penetrates into dermis

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Hair

• Root and Shaft contain three layers
• Inner medulla(may lack in thin hair), cortex
  (contains pigment granules), and cuticle

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Hair

• Hair Follicle
• Surrounds the root of the hair
• Contains an external root sheath (continuation of
  epidermis) and internal root sheath (produced by
  the matrix)

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Hair

• Bulb
• Contains papilla of hair (areolar connective
  tissue and blood vessels to nourish hair)
• Contains matrix (produce new hairs)

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Hair

• Sebaceous glands and arrector pili muscle
  associated with hairs

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Hair

• Arrector pili muscle responsible for goose
  bumps

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