INTEGUMENT

I. INTRODUCTION (fig 5.1)

-- integument = skin (cutaneous membrane)

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

-- Skin may be thick or thin

-- It’s the largest organ in the body

II. FUNCTIONS OF INTEGUMENT

(get into groups of 4-6 and brainstorm!)

III. LAYERS OF INTEGUMENT (fig. 5.6)

A. Epidermis (epi=on, derma=skin)

-- topmost/uppermost layer

-- 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 integument

-- stores fat and helps anchor skin

-- areolar CT and adipose tissue

IV. CELLS OF EPIDERMIS (fig. 5.2, 5.4)

1) Keratinocytes

* most numerous: (90%)

* found throughout all layers of epidermis

* produce keratin

2) Melanocytes

* about 8%

* in stratum basale only

* produce melanin

3) Tactile Cells (Merkel cells)

* in stratum basale only

* tactile (touch) sensation

4) Epidermal dendritic cells (Langerhans cells)

* in stratum spinosum

* phagocytize (ingest) bacteria and foreign debris

V. LAYERS OF EPIDERMIS (fig. 5.2)

1) Stratum Basale (basal layer)

* single layer of cuboidal keratinocytes resting on basement membrane

* keratinocytes constantly dividing mitotically

* also contains melanocytes, tactile cells

2) Stratum Spinosum (spiny 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 in thick skin

* 2-3 layers of pale, flattened, anucleate keratinocytes

5) Stratum Corneum (hornlike layer)

* 25-30 layers of dead, anucleated keratinocytes

* outer keratinocytes are constantly shed

VI. LAYERS OF DERMIS (fig. 5.6)

1) Papillary Layer

* most superficial layer

* dermal papillae

2) Reticular Layer

* contains secretory portion of sweat glands, oil glands, & hair follicles

VII. EPIDERMAL DERIVATIVES

A. Hair (fig. 5.9)

* functions:

B. Nails (fig. 5.8)

* formed from ______________

* functions:

C. Exocrine Glands (fig 5.8)

1) Sebaceous (oil glands)

* holocrine glands

* associated with hair follicles

* secrete sebum (oil)

* functions:

2) Sweat 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 exposed to sunlight

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