The Integumentary system

The Integumentary system

1. Functions

   • 1. protection
     • BY EVERYTHING. the primary goal of the integumentary system
   • 2. sensation
     • (part of nervous system)
       • Cutaneous sensory receptors (corpuscles)
         • Tactile corpuscles (scratchy etc sensations)
         • Lamellar corpulus (pressure)
         • hair follicles (so we can feel the breeze)
   • 3. blood storage
     • 5% of blood is stored in dermis
       • exercise
         • nervous system constricts dermal blood to bring into circulation
     • homeostatic inbalances
       • cyanosis (caucasians) (blood that has less oxygen turns darker)
         • heart failure/poor circulation/severe respiratory issues
       • Jaundice (yellow bile accumulates in blood stream)
         • liver disorder
       • erythema (blood vessels expand)
         • fever, inflammation, allergy
       • due to difference in skin color, sometimes easier to spot in mucous membranes or finger/toenail beds
   • 4. temperature regulation
     • cold
       • blood vessels in skin
         • Vasoconstriction brings blood deeper into tissue to help vital organs keep warm. Vasodilation when done.
           • blue fingertips etc.
     • sweat
       • insensible perspiration: half a liter of sweat each day
       • sensible perspiration: up to 12 liters a day
   • 5. vitamin D synthesis
     • skin color
       • closer to poles, lighter, closer to equator, darker
       • Skin + UV
         • becomes activated D, or Calcitriol on reaching liver, kidneys, through bloodstream
           • circulated to bones (absorbs calcium, promote bone growth)
   • 6. excretion
     • Sweats small amounts of nitrogen containing waste ex, urea, uric acid, ammonia
       • No evidence heavy sweating leads rids of extra toxins

2. Skin

   • Epidermis (stratified squamous tissue)
     • Cells
       • Keratonocytes: building blocks of protein keratin
       • Melanocytes: synthesized melanin pigment (skin color) (in stratum basale)
         • Skin color is determined by the breadth. wider breadth = more melanin content
       • Langerhan cells
         • Secreted by bone marrow
       • Merkel cells: combines with nerve endings = sensory receptors
     • Layers
       • Come Let's Get Sun Burned
         • corneum "upper"
           • ker- (1) "horn; head, uppermost part of the body"
           • 20-30 layers of dead keratinocytes
         • Lucidum "clear"
           • Only in palms / footsoles
         • granulosum "grainy"
           • grainy because they are compressed/flattened as they go
         • Spinosum "spiny"
           • Spiny because filaments make them hold on to each other. Active mitosis found here!
         • basale "basal"
           • cell factory
         • Sunburn
           • Ultraviolet radiation
             • damages epidermis, causing elastic filaments to clump up
             • Skin cancer
             • Immune system drop
       • Old at top, young at base
         • AVASCULAR
   • Dermis (collagen/elastic fibers)
     • Reticular layer 80% of dermis (dense irregular connective tissue)
       • Nerve fibers
       • Blood vessels
       • Hair
       • Oil
       • sweat glands
     • Papillary layer (areolar connective tissue)
       • Dermal pillae form friction ridges...
         • Fingerprints!
   • Hypodermis (adipose connective tissue) / subcutis
     • Anchors skin etc, insulation, shock absorption, FAT

3. Skin appendages

   • hair (pili)
     • cuticles (conditioner)
     • root in skin pushes out dead keratin protein cells (shaft)
   • nails
     • looks pink because of capillaries underneath
     • lunule "little moon" is where the nail matrix where growth originates
   • 3 million sudoriferous / sweat glands
     • Eccrine
       • abundant, in hands, soles of feet, forehead
     • Apocrine
       • ~2000 of these, emptying into hair follicles near armpits and groin around puberty
         • sweat contains fats and proteins, so they stink
       • modified Apocrine:
         • mammary glands: secretes milk
         • cerunous glands: earwax (cerumen)
   • sebaceous (oil) glands
     • everywhere but hands and feet
     • pimples, though primary goal is to soften/lubricate skin and hair, slow water loss in dry environments
     • empty into hair follicles

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