Health Sciences 2330A/B Lecture 2: The Integumentary System

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Week 2 – January 15th, 2016 Virginia Polihronova
The Integumentary System
Week 2 – January 15th, 2016
Virginia Polihronova
The Skin (Cutaneous Membrane)
-Two layers:
oEpidermis
Visible to the eye
Avascular epidermis
oDermis
Connective tissues underneath the epidermis
Vascular dermis
-Functions:
oRegulate temp, stores blood, protects the body from external environment,
detects cutaneous sensations, excretes and absorbs substances (ex. sweat),
synthesizes vitamin D
-Largest organ in the body (skin)
-Holds up to 7% of TBV (total blood volume)
-Thickness ranges throughout the entire body
oFinger and foot pads have the thickest layers of skin
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Week 2 – January 15th, 2016 Virginia Polihronova
Structure of the Skin – 4 Major Types of Cells in the Epidermis
- Keratincytes
oMakes up 90% of the cells
oProduce keratin
Tough, fibrous, intracellular protein that helps protect skin and
underlying tissues from abrasions, heat, microbes, and chemicals
oProduce lamellar granules
Release water-repellant sealant that decreases water entry and water loss
Inhibits passage of foreign materials
oProtected from UV damage due to melanin granules of melanocytes
- Melanocytes
oMakes up 8%
oLong projections transfer melanin granules to neighbouring keratinocytes
Once inside – cluster to form protective veil over nucleus on side
toward skin surface shields DNA from UV damage
oProduce melanin
Yellow-black or brown-black pigment that contributes to skin colour
Higher production of melanin darker pigmentation
Absorbs damaging UV light
oEasily damaged by UV light
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Week 2 – January 15th, 2016 Virginia Polihronova
- Intraepidermal macrophage or Langerhans
oArise from bone marrow – migrate to epidermis
oParticipate in immune responses mounted against microbes that invade the skin
oEasily damaged by UV light
- Tactile epithelial or Merkel cells
oLeast common
oLocated in deepest layer of epidermis
oIn contact with sensory neuron (tactile Merkel disk)
oDetect touch sensations
Layers of the Epidermis
-Thin skin
o4 layers – stratum basale,
stratum spinosum, stratum
granulosum, thin stratum
corneum
oIn most regions of the body
-Thick skin
o5 layers – stratum basale,
stratum spinosum, stratum
granulosum, stratum lucidum, thick
stratum corneum
oIn parts of skin where there is
greatest exposure to friction
Fingertips, palms,
soles, etc.
-Stratum Basale
oDeepest layer of the
epidermis
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