CH 5 Integumentary System

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CH 5 Integumentary System
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General Characteristics

• The integumentary system includes the skin and
  its accessory organs.
• The skin includes the epidermis, dermis and
  hypodermis (subcutaneous layer).
• The skin is the largest organ of the body
• Approximately 22 ft2
• Approximately 16 of total body weight
• 0.5mm-4 mm thick
• Thickest regions hands and feet
• Thinnest regions eyelids and scrotum

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THE SKIN
Epidermis
Dermis
Subcutaneous (Hypodermis)
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Skin Functions

• Thermoregulation regulation of body temperature.
• Most important function
• Excess heat is carried to the skin by the blood
  vessels.
• Skin absorbs heat and transfers it to the
  surrounding air.
• Protection acts as a barrier against physical
  trauma, chemical and biological substances.
• Works the best as a barrier when it is intact- no
  cuts, scrapes, etc..
• Approximately 50 layers of cells.

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Skin Functions

• Sense organ provides the body with cutaneous
  sensations.
• Sensations of touch, vibration and pain
• Collects information from the outside world and
  sends it to the brain
• What part of the body is the most sensitive?
• Lips
• Genitals
• Hands/Feet

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Skin Functions

• Secretion and absorption allowing certain
  materials to pass into or out of the skin.
• Secretion
• Secretes water and oils through glands.
• Can remove some waste like salts, urea, carbon
  dioxide and heat.
• Absorption
• Taking materials into the body through the skin.
• Most absorbed- fat soluble vitamins (A, D, E, K)
• Some toxins are absorbed- rubbing alcohol,
  acetone, chlorine

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Skin Functions

• Vitamin D production a precursor to the vitamin
  D molecule can be found within the skin.
• When exposed to sunlight, the precursor becomes
  vitamin D because the light energy transforms its
  shapes.
• It takes hours of sun exposure to produce the
  amount of vitamin D in a glass of milk. Is it
  worth it?

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General Characteristics and Function of the
Epidermis- outer layer of skin

• 40-50 layers of stratified squamous epithelial
  tissue.
• Avascular
• Designed to be shed and replaced frequently
• Waterproof
• Function Protection

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Cells of the Epidermis

• Keratinocytes- cells that produce keratin.
• These cells make up 90 of the epidermis
• Keratin is a tough, fibrous, water-proof protein
• Most keratinocytes are dead
• They dont really become flattened until they
  reach the top layers due to pressures from above
  and below as the cells move up the epidermis.
• Keratinization the process by which the
  cytoplasm and organelles of a keratinocyte are
  replaced by keratin.
• Happens as cells move up through the epidermis
• This is what eventually kills the keratinocytes

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Cells of the Epidermis

• Melanocytes- cells that produce melanin.
• Function to protect the skin from UV radiation
• Produce melanin- a brown, black pigment
• It is produced by positive feedback. The more
  exposure- the more melanin produced- which means
  the more the skin can be exposed to the sun.
• We all have the same of melanocytes per square
  inch of the skin. Our melanocytes just produce a
  varying amount of melanin.
• Langerhans cells- immune cells
• Function to protect the body from foreign
  particles
• These are phagocytes- engulf and destroy

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Cells of the Epidermis

• Merkel cells- touch cells.
• Function to gather information (touch,
  temperature, vibration, and pain) and send it to
  the brain to be interpreted.
• Melanocytes, Langerhans cells and Merkel cells
  account for the remaining 10 of the epidermis.

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Layers of the Epidermis- from the bottom to top

• Stratum Basale- deepest layer
• Simple cuboidal layer
• Lies above the dermis and blood vessels in the
  dermis supply this layer with blood (by
  diffusion)
• Here is where cell division takes place,
  producing new skin cells and pushing older cells
  toward the surface.
• Stratum Spinosum- superficial to the stratum
  basale.
• 8-10 layers
• Cells have small projections spiny that help
  lock the cells together like velcro.

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Layers of the Epidermis- from the bottom to top

• Stratum Granulosum- superficial to the stratum
  spinosum.
• 3-5 layers
• Cells are starting to look more squamous because
  of pressure from the cells above and below.
• Layer where keratinization starts and cells
  produce keratin in large quantities.
• Can see granules of keratin in the cells.
• The transition layer between living and dead
  cells.

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Layers of the Epidermis- from the bottom to top

• Stratum Lucidum- superficial to the stratum
  granulosum.
• 3-5 layers
• Only found on the soles and palms
• Shock absorbers
• Stratum Corneum- the most superficial layer of
  the epidermis
• 25-30 layers of squamous keratinocytes
• Spines start to break off which causes the cells
  to fall off
• Waterproofs the skin
• Takes 5 weeks for cells to reach this layer from
  the stratum basale

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LAYERS OF EPIDERMIS
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Dermis- Inner Layer of Skin

• General Characteristics
• Thicker than the epidermis
• Composed of connective tissue
• Highly vascular
• Contains all accessory organs necessary for skin
  function (nerves, blood vessels, glands, hair
  follicles)
• Thats why burns that extend into the dermis are
  much more severe. They interfere with skins
  ability to function.

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Dermis continued.

• Function
• Supports the epidermis by keeping the dividing
  cells of the stratum basale healthy
• Regulates body temperature
• Provides skin with its strength and flexibility

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Dermis continued.

• Layers of the dermis
• Papillary region lies deep to the stratum basale
  of the epidermis
• 20 of the thickness of the dermis
• Composed of areolar connective tissue with thin
  collagen and fine elastic fibers
• Small capillary (tiny blood vessel) loops to
  supply nutrients to the epidermis
• Contains dermal papillae

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Dermis continued

• Dermal papillae small projections that anchor
  the epidermis to the dermis
• Prevent the epidermis from laterally sliding off
  of the dermis
• Epidermal ridges the ridges that form the
  fingerprints
• Larger, downward projections of the epidermis
  that force some of the dermal papillae sideways
• Function to lock the epidermis in place

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Dermal papillae and epidermal ridges
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What type are you?
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• Reticular layer lies deep to the papillary
  region
• Includes the remaining 80 of the dermis
• Composed of dense irregular tissue
• Collagen fibers run in various directions which
  adds strength
• Functions to house the accessory organs of the
  skin and provide the skin with strength and
  flexibility

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ACT-UP

• Knowing what you know about the skin, answer the
  following questions
• 1) Why would a person with tattoos not need to
  have them retouched every five weeks?
• 2) What would cause them to fade over time?

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Accessory Structures of the Skin

• Hair- present on most surfaces of the skin
• Shaft is the hair above the skin (dead
  keratinocytes)
• Root is the hair below the skin
• Follicle- Layers that surround and protect the
  hair root
• Matrix- The dividing cells of the hair root that
  cause hair growth
• Papillae- Small projections that anchor each
  hair.
• Contain blood vessels that keep the matrix alive.

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Accessory Structures of the Skin

• Hair function
• Insulates against heat loss
• Protects from UV radiation
• Arrector pili muscle A small muscle attached to
  the bulb of a hair.
• Attaches to the follicle sheath
• Contracts under physiological or emotional
  stress, which pulls the hair shafts perpendicular
  to the skin surface.

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Glands- Present in different concentrations in
all areas of the skin

• Sebaceous glands oil glands
• Associated with hair follicles
• Function to produce oil (sebum)
• Keeps hair soft and flexible
• Keeps skin around the hair soft and flexible
• Destroys some bacteria

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• Sudoriferous glands sweat glands
• Function to release a watery secretion (sweat) to
  cool the body.
• Two types
• Eccrine- Respond to elevated body temperatures
• Apocrine- Respond to stress (adrenaline rush)
• These release sweat along with some proteins and
  fat that bacteria LOVE! As bacteria feed on this
  thick sweat, they produce a stinky by-product
  B.O.!!

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• Ceruminous glands modified sweat glands that are
  only found within the external ear canal
• Function to produce cerumen (wax) that protects
  the eardrum by trapping substances.
• Its important to keep this production at a low
  level- so water doesnt get trapped that will
  support the breeding of bacteria.

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