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The integumentary system, encompassing the skin, protects the body, regulates temperature, and acts as an indicator of health. With its various layers and structures, the skin plays a crucial role in sensation, absorption, and excretion. Understanding its functions, from large blood supply for thermoregulation to vitamin D synthesis, is key to overall well-being.
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The integumentary system • Protection • Thermoregulation • Indicator of health • Hypoxia • Rashes • Disorders of the skin
Functions of the skin • Regulation of body temperature • Large blood supply (associated with thermoregulation) • Protection • Sensation (cutaneous receptors) • Excretion and absorption • Vitamin D synthesis
Largest organ of the body • epidermis= epithelial tissue • Dermis=connective tissue • Hypodermis(subcuta-neous layer)=areolar and adipose tissue • Hypodermis attaches to underlying tissues
Epidermis • Keratinocytes • 90% of epithelial cells • Protection, durability • Melanocytes • Melanin protects against UV • Langerhans cells • Immune cells • Merkel cells • touch
Epithelial layers (strata) • Stratum basale (stratum germinativum) new cell formation; keratinocytes • Stratum spinosum “spiny” • Stratum granulosum- cells are dying; producing keratin and lipid • Stratum lucidum- only in thick skin. Lots of keratin • Stratum corneum- many layers of dead cells; water repellent
Dermis • Contains lots of collagen and elastic fibers • Papillary region (areolar) • Meissner corpuscles (touch) • Free nerve endings • Reticular region (dense) • variety of cells and glands • Epidermal ridges form fingerprints
Skin color • People have same number of melanocytes but different amount of melanin • Carotene- yellowish tint • Hemoglobin-reddish tint • Albinism- no melanin • Vitiligo- irregular loss of melanin • Changes in skin tone may be significant • Cyanosis • Jaundice • Rash
Hair • Dead, keratinized cells • Medulla, cortex, cuticle • Shaft is what you see • Bulb is base of hair follicle • Papilla contains blood vessels • Matrix source of new cells
Hair growth is cyclical • Lanugo formed (and lost) before birth • Vellus hairs (“peach fuzz”) • Terminal hairs • Head, eyebrow, lashes, pubic • More terminal hair on body in males than females • Hair color, balding patterns are inherited
Glands of the skin sudoriferous
Earwax is produced by modified sweat glands! • Ceruminous glands • Secrete into external auditory meatus • Helps protect ear from foreign objects
Nails • Free edge, nail body, nail root • Hyponychium holds nail onto fingertip • Eponychium is cuticle
Skin is not uniform over the body • Thin skin is hairy • No stratum lucidum • Few epidermal ridges • Hair follicles present • Many sebaceous, fewer sudoriferous glands • Thick skin is hairless • More sensory receptors, more sweat glands
Blood supply to integumentary system • None to epidermis • Some plexuses supply blood to dermis; usually offshoot of supply to muscle • Cutaneous plexus between dermis and subQ • Papillary plexus extends into dermis
Developmental aspects of integument • Epidermis formed from ectoderm, dermis from mesoderm • Effects of aging usually occur in dermis • Collagen and elastic fibers break down • Immune function decreases • Glands secrete less
Damage to skin may be diagnostic • Wheal (hives) • Vesicles (viral infections) • Dermatitis, pruritis (allergic reaction) • Type of rash may help diagnose infectious disease • Condition of nails or hair may indicate disease • Contact dermatitis
Introducing material to skin (barrier properties of skin) • Intradermal- within dermis • TB tests • Allergy tests • Economical way to give vaccines? • Subcutaneous • Little blood supply • Slow absorption, e.g. insulin • Intramuscular • Large doses • Rapid absorption • Transdermal • Timed release • No needles!
Summary • Skin protects the internal structures • Skin helps maintain body temperature • Storage (of fat) secretion (of salts, water and wastes) and synthesis (of vitamin D) are important features • Many different types of nerve endings allow distinction of touch, pressure, pain and temperature.