TIS

Chapter 1 Geriatrics: Section III - Integument

I. INTRODUCTION

-- skin = integument

Integumentary System = Skin + Glands + Hair + Nails + associated Blood Vessels + associated Nerves

-- Skin is of varying thickness - it may be thick or thin

-- It's the largest organ in the body

II. FUNCTIONS OF INTEGUMENT

1) Protection

2) Waterproof (Hydroregulation)

3) Temperature Regulation
* heat lost by:

1) radiation (through blood vessels)
2) perspiration
3) conduction of heat directly through skin

* heat is conserved by:

1) constriction of blood vessels

4) Secretion

* waste products

* sebaceous glands secrete sebum (oil)

5) Selective Absorption

6) Sensory Reception

III. 3 LAYERS OF INTEGUMENT

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

-- topmost/uppermost layer

-- stratified squamous epithelium

-- avascular

-- consists of 4 or 5 layers:

* thick skin - five layers
* thin skin - four layers

B. Dermis

-- middle layer

-- dense irregular connective tissue

-- contains many blood vessels

-- contains nerve endings, hair follicles, glands

-- papillae (projections of dermal tissue into the epidermis)

C. Hypodermis (hypo=under)

-- deepest layer

-- loose CT and adipose tissue

IV. LAYERS OF EPIDERMIS

1) Stratum Basale (basal layer)

* single layer of cuboidal cells resting on basement membrane
* cells constantly dividing mitotically

2) Stratum Spinosum (spiny layer)

* 2-3 layers of polygonal-shaped cells
* cells still alive in this level

3) Stratum Granulosum (granular layer)

* 3-4 layers of granular, flattened cells
* cells 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 flattened, anucleate cells

5) Stratum Corneum (hornlike layer)

* 25-30 layers of dead, anucleated cells
* outer cells are constantly shed

V. CELLS OF EPIDERMIS

1) Keratinocytes

* most numerous: (90%)
* found throughout all layers
* produce keratin

2) Melanocytes

* about 8%
* stratum basale
* produce melanin

3) Tactile Cells (Merkel Cells)

* only a few cells
* stratum basale
* aid in tactile (touch) sensation

4) Nonpigmented Granular Dendrocytes (Langerhans Cells)

* only a few cells
* stratum spinosum
* ingest bacteria and foreign debris

VI. LAYERS OF DERMIS

1) Papillary Layer

* most superficial layer
* has papillae

2) Reticular Layer

* deep to papillary layer
* sweat glands, oil glands, & hair follicles

VII. EPIDERMAL DERIVATIVES

A. Hair

* bulb, root, and shaft
* function: protection

B. Nails

* formed from stratum corneum
* function: protection and grasping

C. Exocrine Glands

* found in dermis
* 3 kinds:

1) Sebaceous (oil glands)

* holocrine glands
* associated with hair follicles
* secrete sebum (oil)
* functions: lubrication and waterproofing

2) Sweat Glands

a) Eccrine (Merocrine)

* found throughout most of skin
* release perspiration

b) Apocrine

* axillary and pubic regions
* release odiferous secretion

3) Ceruminous

* in external auditory canal
* secrete cerumen (earwax)

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