Integumentary System

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					1    Chapter 5 Integumentary System

    An Introduction to the Integumentary System

       1. The integumentary system, or integument, consists of the cutaneous membrane, which includes the
          epidermis and dermis, and the accessory structures. Beneath it lies the subcutaneous layer (or hypodermis).
              a. Five major functions of the integument
                      i. Protection

                       ii. Temperature maintenance

                      iii. Synthesis and storage of nutrients

                      iv. Sensory Reception

                       v. Excretion and secretion

    5-1 The epidermis is composed of strata (layers) with various functions

       2. Thin skin covers most of the body; heavily abraded body surfaces may be covered by thick skin.
       3. Thick skin has five layered
              a. Stratum germinativum - attached to the basement membrane

              b. Intermediate Strata

                       i. Stratum spinosum

                      ii. Stratum granulosum

                      iii. Stratum lucidum

              c. Stratum corneum

       4. As epidermal cells age, they move up through the stratum spinosum, the stratum granulosum, the stratum
          lucidum, and the stratum corneum. In the process, they accumulate large amounts of keratin. Ultimately the
          cells are lost or shed.
       5. Epidermal ridges interlock with dermal papillae of the dermis. Together, they form superficial ridges on the
          palms and soles that improve the gripping ability of the hands and feet.

    5-2 Factors Influencing skin color are epidermal pigmentation and dermal
       6. The color of the epidermis depends on two factors:
              a. melanin

              b. carotene
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       7. Melanocytes protect stem cells from ultraviolet (UV) radiation.

    5-3 Sunlight has detrimental and beneficial effects on the skin.
       8. Epidermal cells synthesize vitamin D3 when exposed to sunlight.
              a. Vitamin D absorbed, modified, and released by the liver & is then converted into calcitriol in the kidneys

               b. Inadequate vitamin D you can have abnormally flexible and weak bones

       9. Skin cancer is the most common form of cancer.
              a. Basal cell carcinoma – originates the stratum germinativum

               b. Squamous cell carcinoma- most superficial skin cancer; fairly common

               c. Malignant melanoma- most dangerous type of skin cancer; usually found in moles, but may be found

                   anywhere on the body

    5-4 The dermis is the tissue layer that supports the epidermis.
       10. The dermis consists of
              a. Papillary layer

                       i. Contains :

                               1. Loose connective tissue

                               2. Capillaries for the dermis & epidermis

                               3. Nerve supply to the dermis & epidermis

                       ii. Supports & nourishes the overlying epidermis.

               b. Reticular layer

                       i. Contains:

                               1. Elastic fibers- flexibility

                               2. Collagen fibers- limit flexibility to prevent damage

                       ii. Fibers are oriented to resist tension in the skin.

       11. Components of other organ systems that communicate with the skin are in the dermis.
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    5-5 The hypodermis is tissue that connects the dermis to underlying tissues.
       12. The hypodermis, or subcutaneous layer, stabilizes the skin’s position against underlying organs and tissues.
              a. Consists of:
                     i. Loose connective tissue & has many many fat cells

    5-6 Hair is composed of keratinized dead cells that have been pushed to the surface.
       13. Hairs originate in complex organs called hair follicles
               a. Hair & several other structures such as those listed below are considered accessory structures of the
                        i. Hair follicles

                       ii. Sebaceous glands

                      iii. Sweat glands

                      iv. Nails

               b. Found almost everywhere except
                      i. Soles of feet

                       ii. Palms of your hands

                      iii. Lips

               c. Parts of the hair

                       i. Hair root

                       ii. Hair shaft

                      iii. Cuticle

                      iv. Cortex

                       v. Medulla

                      vi. Arrector pilli muscle

               d. Functions of Hair

                       i. Help protect the scalp from uv light

                       ii. Help cushion the skull from light blows

                      iii. Prevent the entry of foreign particles (inside your nose & ears)

                      iv. Early-warning system that may help prevent injury
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       14. Our hairs grow and are shed according to the hair growth cycle. A single hair grows for 2-5 years and then is
       15. Hair color

               a. Produced by differences in the amount and type of pigments produced by melanocytes

               b. Pigment differences are genetic but environmental factors may also affect this

    5-7 Sebaceous glands and sweat glands are exocrine glands found in the skin.
       16. Sebaceous Glands
              a. Holocrine glands that discharge an oily lipid

               b. Discharge the lipid onto both skin and into hair follicles

               c. Secretion is called sebum; purpose is to lubricate the hair and skin and also inhibits the growth of


               d. Sebaceous follicles

                        i. Discharge sebum directly onto the skin

                       ii. Located on your face, chest, back

       17. Sweat Glands
              a. Apocrine sweat gland

                        i. Secrete their products into hair follicles in the arm pit & groin area (associated with a hair


               b. Merocrine sweat glands

                        i. Palms of your hands and soles of your feet (this is where they are the most frequent)

                       ii. Discharge secretions directly onto the skin ( not associated with a hair follicle)

                       iii. Primary Function: to cool the surface of the skin and lower body temperature

       18. Sweat provides protection from environmental hazards.

    5-8 Nails are keratinized epidermal cells that protect the tips of fingers and toes.
       19. The nail body of a nail covers the nail bed. Nail production occurs at the nail root.
               a. Nails

                        i. Form on the dorsal surfaces of fingers and toes; protect the exposed tips & help prevent


               b. Nail Body
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                        i. Dense mass of dead, keratinized cells

                        ii. Recessed beneath the surrounding epithelium

                       iii. Covers the nail bed

               c. Nail Bed

                        i. Skin underneath the nail body

               d. Nail Root

                        i. Nail production occurs here

               e. Cuticle

                        i. Flap of skin that covers the base of your nail

               f.   Lunula

                        i. White half moon at the base of the visible nail; lack of blood flow

    5-9 Several steps are involved in repairing the integument following an injury.
       20. 4 steps of Skin Repair
               a. Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an

                    inflammatory response.

               b. Then a scab forms and cells of the stratum germinativum are migrating along the edges of the wound .

                    (after a few hours)

               c. The scab has been undermined by new epidermal cells. ( about one week)

               d. Scab is completely gone, epidermis is complete…,you may see slight marking for a few more weeks

       21. Effects of Burns
               a. The severity of a burn depends on
                        i. Depth of penetration

                        ii. The total area affected

               b. Classification of Burns
                       i. First-Degree Burns

                                1. Superficial epidermis is killed, injury of the deeper layer of epidermis & very upper layer

                                    of the dermis

                                2. Skin would be inflamed and tender
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                      ii. Second-degree Burns

                             1. Superficial and deeper cells of the epidermis and maybe some of the dermis are killed;

                                 the damage may extend into the reticular layer of the dermis (most accessory

                                 structures are unaffected)

                             2. Blister; very painful

                     iii. Third-degree burn

                             1. All epidermal and dermal tissue is destroyed

                             2. Injures your hypodermis and deeper tissue and organs

                             3. Charred; no sensation at all

    5-10 Effects of aging include dermal thinning, wrinkling, and reduced melanocyte activity.
       22. Major age-related changes include:
              a. Skin injuries and infections become more common
              b. The sensitivity of your immune is reduced.
              c. Muscles become weaker, and bone strength decreases
              d. Sensitivity to sun exposure increases
              e. The skin becomes dry and scaly
              f. Hair thins and changes colors
              g. Sagging and wrinkling of the skin occur
              h. The ability to lose heat decreases
              i. Skin repair proceeds very slowly

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