Integumentary System

1. Integumentary System Skin and accessory structures (hair, nails) Integument means covering

2. Functions • Protection • Against UV light, entry of pathogens, abrasions, water loss • Sensation • Sensory receptors detect heat, cold, touch, pressure, pain • Temperature regulation • By controlling blood flow and sweat glands • Vitamin D production • In UV light, skin produces a molecule that can be transformed into Vitamin D

3. Vitamin D • Necessary for normal absorption of calcium from intestine • Rickets in children is a disease from reduced mineralization of bone matrix

4. The skin consists of 2 layers 1. Epidermis • Outer layer • Stratified squamous • Contains no blood vessels • Has four types of cells • Most cells are Keratinocytes • Produce keratin • Melanocytes • Skin color, produced from melanin • Langerhans’ cells • Part of the immune system • Merkel’s cells • Detect light and pressure

5. Epidermis • Cells are produced by mitosis in the deepest layer • New cells push older, dead cells to surface to slough off or desquamate • Keratinization is the process of moving older cells to surface because they fill with keratin. • These cells will resist abrasion and form a permeability barrier

6. 5 layers of epidermal cells • Strata are regions of the epidermis • Stratum Corneum • Stratum Lucidum • Stratum Granulosum • Stratum Spinosum • Stratum Basale

7. An easy trick to remember these 5 epidermal layers in order from the most superficial to the deepest: "Can Little Girls Speak British" • Can Corneum • Little Lucidum • GiRl GRanulosum • Speak SPinosum • British Basale

8. Stratum Corneum • 25 + layers of dead skin • Cornified cells (dead cells with a hard protein envelope) • Hard keratin (nails, hair) • Soft keratin (skin)

9. Stratum Lucidum • Thin, clear region • Dead cells • Only found in thick skin (palms, soles of feet, fingertips)

10. Stratum granulosum • 2-5 layers of diamond shaped cells • Most cells are dead • Keratohyalin granules • protein envelope that forms below plasma membrane

11. Stratum spinosum • 8-10 layers of flatten cells • Some mitosis occurs • Lamellar bodies form (organelle containing lipids) • Abundant Langerhans cells

12. Stratum basale • Deepest layer • Single layer of cuboidal/columnar cells • Mitosis occurs every 19 days • One daughter cell pushes to surface to become keratinized (40-56 days) • Contains merkel cells and melanocytes

13. Thick and Thin Skin • Thick • All 5 strata • Areas subject to pressure and friction (soles of feet, palms of hands, fingertips) • Thin • 4 layers • Hair present • Callus is increased layer of strata corneum

14. Hypodermis • Subcutaneous tissue • Not a part of skin • Foundation for dermis • Supplies blood vessels and nerves • Adipose abundant • Half of body fat

15. Dermis • Deeper layer • Exchanges gases, nutrients, wastes from epidermis • Comprised of 2 layers • Responsible for strength and flexibility

16. 2 layers of dermis • 1. Reticular region • Collagen and elastin fibers • Dense, irregular connective • Cleavage/tension lines • Stretch marks (overstretched, ruptured dermis) • 2. Papillary region • Papillae projections • Loose connective • Makes your fingerprints

17. Skin color • Melanosomes (vesicle for carrying melanin) are produced by Golgi apparatus of the melanocytes • Melanin is a term used to describe a group of pigments responsible for color of hair, skin, eyes. (UV protection) • Melanosomes move into cell processes of the melanocyte • Epithelial cells phagocytize melanosomes • Production due to genes, hormones, sun exposure

18. Skin color • Freckles = large amounts of melanin • Albinism = inability to produce melanin • Tanning= UV light darkens melanin and stimulates production • Carotene = yellow pigment in carrot/ corn that accumulates in stratum corneum and tints skin yellow • Cyanosis = bluish color from shock due to decrease in blood oxygen