INTEGUMENTARY SYSTEM

INTEGUMENTARY SYSTEM

1. FUNCTIONS

   • Protects underlying tissues and organ
   • Excretes salts, water and wastes
   • Maintains body temperature
   • Synthesis of vitamin D3
   • Detects touch, pressure, pain and temperature

2. 2 MAJOR COMPONENTS

   • Cutaneous membrane (skin)
     • EPIDERMIS
       • avascular
       • consists of stratified squamous epithelium
       • its surface consists of dead cells packed with the tough protein keratin
       • cell types
         • keratinocytes
           • produce keratin for strength
           • formed the lowest layer of the epidermis
           • become dead and scale-like
         • melanocytes
           • produce pigment for skin colour
         • stem cells
           • undifferentiated cells that divide and give rise to keratinocytes
           • found only in depest layer of epidermis - stratum basale
         • Dendritic (Langerhans') cells
           • part of the immune system
           • guard agains toxins, micobes and other pathogens that penetrate into skin
         • Tactile (Merkels's) cells
           • detect light, touch and pressure
       • Layers of epidermis
         • Sratum corneum (outermost layer)
           • the "horn" layer
           • found at surface of thick and thin skin
           • shed an replace every 2 weeks
           • 15 to 30 layers of keratinized cells
         • Stratum Lucidum
           • the "clear" layer
           • found only in thick skin (palms and soles)
           • covers stratum granulosum
           • flat, densely packed and filled with keratin
         • Stratum Granulosum
           • the "grainy" layer
           • consists of 3-5 layers of keratinocytes displaced from the stratum spinosum
           • stops dividing, starts producing
           • manufacturing large quantities of proteins keratohyalin and keratin
         • Stratum spinosum
           • the "spiny" layer
           • contains Langerhans cells
           • continue to divide, increasing thickness of epithelium
           • produce by division of stratum germinosum
         • Stratum Germinativum
           • the "germinative" layer
           • has many germinative (stem) cells
           • contains Merkels cells that respond to touch
           • contains melanocytes which contain melanin pigment
     • DERMIS
       • the papillary layer
         • consists of areolar tissue
         • contains smaller capillaries, lymphatics and sensory neurones
         • has dermal papillae projecting betwwen epidermal ridges
       • the reticular layer
         • consists of dense irregular CT
         • Large blood vessels, lymph vessels and nerve fibers
         • collagen and elastic fiber
     • HYPODERMIS
       • Consists of areolar and adipose tissue
       • site of subcutaneous injections using hypodermic needles
   • Accessory structures
     • Hair
       • functions
         • protects and insulates
         • guards openings against particles and insects
         • sensitive to a light touch
       • hair follicle
         • located deep in dermis
         • base surrounded by sensory nerves
       • Accessory
         • arrector pili
           • involuntary smooth muscle
           • causes hair to stands up and produces "goosebumps"
         • sebaceous glands
           • lubricate the hair
           • control bacteria
     • Glands
       • sebaceous gand
         • oily secretion (SEBUM) for lubrication, keeps hair moist and prevent skin drying
       • Apocrine sweat glands
         • produce sticky, milky white substance and odorous secretion
       • merocrine sweat glands
         • discharge secretion directly onto surface of skin. eg : palms and soles
       • mammary gland
       • ceruminous glands
         • secretion is cerumen (ear wax)
     • nails

3. skin colour

   • the pigments of carotene and melanin
   • blood circulation

4. EFFECTS OF AGING

   • Epidermis thin
   • no of Langerhans cells decreased
   • Vitamin D3 production decreased
   • melanocytes and glandular activity declines