I. INTRODUCTION
    -- integument = skin (cutaneous membrane)

        Integumentary System = Skin, Exocrine Glands in skin, Hair and Nails

    -- Skin may be thick or thin

    -- the largest organ in the body
 

II. FUNCTIONS OF INTEGUMENT
 
 
 
 
 
 
 
 
 
 

III. LAYERS OF INTEGUMENT
    A. Epidermis (epi=on, derma=skin)
        -- topmost/uppermost layer
        --keratinized stratified squamous epithelium
        -- avascular
        -- consists of 4 or 5 layers:
            * thick skin (thick epidermis)
            * thin skin (thin epidermis)
        -- epidermal ridges

    B. Dermis
        -- layer deep to epidermis
        -- primarily dense irregular connective tissue
        -- contains nerve endings, hair follicles, glands
        -- dermal papillae
 

C. Subcutaneous Layer (Hypodermis, Superficial fascia)

--  technically not part of the integument, but a layer DEEP to integument
-- stores fat and helps anchor skin
-- areolar CT and adipose tissue

V. CELLS OF EPIDERMIS
    1) Keratinocytes
        * most numerous (90%)
        * found throughout all layers
        * produce keratin
 

    2) Melanocytes
        * about 8%
        * in stratum basale only
        * produce melanin
 

    3) Tactile Cells (Merkel cells)
        * stratum basale only
        * tactile (touch) sensation
 

    4) Epidermal Dendritic Cells (Langerhans cells)
        * stratum spinosum
        * phagocytize (ingest) bacteria and foreign debris
 

REVIEW THIS MATERIAL WITH THE
 EPIDERMAL CELLS MEMORY MATRIX

V. LAYERS OF EPIDERMIS
    1) Stratum Basale (Basal Layer)
        * single layer of columnar/cuboidal keratinocytes resting on basement membrane
        * keratinocytes constantly dividing mitotically
 

    2) Stratum Spinosum (Spiny Layer, Prickly Layer)
        * several layers of polygonal-shaped keratinocytes

* also contains epidermal dendritic cells

    3) Stratum Granulosum (Granular Layer)
        * 3-5 layers of granular, flattened keratinocytes
        * keratinocytes undergo keratinization here

        (keratinization: process where nucleus shrivels up, cell dies, and cell fills up with the protein keratin)
 

    4) Stratum Lucidum (Clear Layer)
        * only seen in thick skin
        * 2-3 layers of pale, flattened, anucleate keratinocytes
 

    5) Stratum Corneum (Hornlike Layer)
        * 20-30 layers of dead, anucleated keratinocytes
        * outer cells are constantly shed
 

REVIEW AND LEARN THE LAYERS OF THE EPIDERMIS BY
COMPLETING THE  EPIDERMIS LAYERS MEMORY MATRIX
 
 VI. LAYERS OF DERMIS
    1) Papillary Layer
        * most superficial layer
        * dermal papillae
 

    2) Reticular Layer
        * contains the secretory portion of sweat glands, oil glands, & hair follicles
 

REVIEW THE CHARACTERISTICS OF THE INTEGUMENT LAYERS
WITH THE  INTEGUMENT LAYERS MEMORY MATRIX
 

VII. EPIDERMAL DERIVATIVES )
    A. Hair


        * functions:
 

    B. Nails
        * formed from _______________
        * functions:
 

    C. Exocrine Glands

        1) Sebaceous (oil glands)
            * holocrine glands
            * associated with hair follicles
            * secrete sebum (oil)
            *functions:

        2) Sweat (Sudoriferous) Glands
            * release perspiration (sweat)
 
   

All of the following are true statements about the integument EXCEPT:

a.  it is water resistant

b.  it is of the same thickness throughout the body

c.  it is the largest organ in the body

d.  the primary (most abundant) cell type in the epidermis is the keratinocyte

e.  it can produce Vitamin D when it is exposed to sunlight
 

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