biology of human aging

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Biology of Human Aging

Chapter 4

The Integumentary System


Outline

1. Review of structure and Function• Epidermis / Dermis

2. Age-related Changes• Epidermal Changes• Dermal Changes• Hypodermal Changes

3. Age-Related DysfunctionsLentigo, Senile Purpura, Senile Angioma, Acrochordon, Senile Pruritus, Senile keratosis, Seborrheic Keratosis, Herpes Zoster, Decubitus Ulcers

4. Skin Cancers• Basal Cell Carcinoma• Squamous Cell Carcinoma• Malignant Melanoma• Secondary Skin Cancer


Introduction/Background Integumentary system comprises the skin, hair, nails & various glands located in the skin. Age change in general appearance of skin wrinkles & sags

Coupled w/ gradual graying of hair reminder of aging changes creams & hair dyes won’t actually delay aging process

Plastic surgery removes some of the aging changes still not helpful!Factors affecting rate and degree of changes in integumentary system: Intrinsic factors

Heredity Dietary habits Levels of various hormones

extrinsic factors Sun and wind (increase potential for skin cancer) use of protective sun-shield lotions


Other factors contributing to aging of skin: 1. Occupation: Extended sun exposure (photoaging)

2. Recreational preference: Boating or sunbathing

Exposure to sun is the major cause of aging changes in the skinExposure to sun is the major cause of aging changes in the skin


Review of Structure and Function

Single most important function: help to maintain a stable internal environment (homeostasis) normal functioning of various cells

Protective covering prevents water loss

Partial barrier blocks the entrance of microorganisms

Pigment cells protect against UV radiation; (Vitamin D)

Sweat glands and network of blood vessels regulate temperature

Temperature rise:

1. blood vessel dilation higher volume of blood to surface heat is lost by radiation from blood to environment

2. Increase in sweat gland activity skin surface becomes wet body heat loss by evaporation

Provides information on external environment to nervous system (through receptors sensitive to pain, temperature, touch)


Process drugs and compounds (smoking patches, seasickness) this function is similar to the function of liver

Part of the immune system (hormone that enhances the growth and development of T cells residing in skin)

Review of Structure and Function


The Integumentary System

Skin: major component of the integumentary system, separates body from external environment via an interrupted covering over entire body

Consists of three major regions:

1. Epidermis – outermost superficial region

2. Dermis – middle region

3. Hypodermis (superficial fascia) – deepest region (a layer of loose connective tissue; attaches dermis to underlying muscles, also fat deposition provides padding & also fat storage)


Skin (Integument)

Figure 5.1


Epidermis• Consists of several layers of thin, flat cells (squamous cells)

form stratified squamous epithelium

• Under constant pressure or friction thickens soles of the feet & palms of the hand calluses and corns

• No blood vessels or nerve fibers; nutrient and waste diffusion

• Inadequate supply (gas & nutrients) to outer cells dead cells gradual replacement of cytoplasm with Keratin,

• Outer-most layer of epidermis composed of thin, dead cells

• All of the cells of epidermis are replaced every 28 days

• Skin color: determined by amount & distribution of melanin • Dark skinned: contain more melanin• Light-skinned people: reddish hue due to blood vessels• Oriental people: variation of melanin that causes their epidermis to have yellowish

hue


Cells of the Epidermis

1. Keratinocytes – produce the fibrous protein keratin

2. Melanocytes – produce the brown pigment melanin

3. Langerhans’ cells – epidermal macrophages that help activate the immune system

4. Merkel cells – function as touch receptors in association with sensory nerve endings


Waterproofing

Protection from abrasion and penetration

Rendering the body relatively insensitive to biological, chemical, and physical assaults

Functions


Dermis

•Located immediately beneath the epidermis, thicker than epidermis

•Second major skin region containing strong, flexible connective tissue (collagenous & elastic fibers)

•Well-supplied with blood vessels, nerves, sweat glands, oil-secreting sebaceous glands

•Specialized receptors provide information concerning touch, pain, pressure, temperature changes to nervous system

•Cell types include fibroblasts, macrophages, and occasionally white blood cells

•Composed of two layers – papillary and reticular


Layers of the Dermis: Papillary Layer

Papillary layer

Areolar connective tissue with collagen and elastic fibers

Dermal papillae contain capillary loops, Meissner’s corpuscles, and free nerve endings


Layers of the Dermis: Reticular Layer

Reticular layer

Accounts for approximately 80% of the thickness of the skin

Collagen fibers in this layer add strength and resiliency to the skin

Elastin fibers provide stretch-recoil properties


Hypodermis

Subcutaneous layer deep to the skin

Composed of adipose and areolar connective tissue


Skin Color

Three pigments contribute to skin color

Melanin – yellow to reddish-brown to black pigment, responsible for dark skin colors

Freckles and pigmented moles – result from local accumulations of melanin


Sweat Glands and Sebaceous Glands

• Sweat Glands Different types prevent overheating of the body

• Sebaceous Glands• Soften skin when stimulated by hormones• Secrete an oily secretion called sebum


Sebaceous Glands

Simple alveolar glands found all over the body

Soften skin when stimulated by hormones

Secrete an oily secretion called sebum


Functions of the Integumentary System

• Protection – chemical, physical, and mechanical barrier

• Body temperature regulation is accomplished by:

1. Dilation (cooling) and constriction (warming) of dermal vessels

2. Increasing sweat gland secretions to cool the body

• Cutaneous sensation – exo-receptors sense touch & pain


Functions of the Integumentary System

1. Metabolic Functions – synthesis of vitamin D in dermal blood vessels

2. Blood Reservoir – skin blood vessels store up to 5% of the body’s blood volume

3. Excretion – limited amounts of nitrogenous wastes are eliminated from the body in sweat


Developmental Aspects of the Integument: Old Age

• Epidermal replacement of cells slows and skin becomes thinner

• Skin becomes dry and itchy

• Subcutaneous fat layer diminishes, leading to intolerance of cold

• Decreased elasticity and loss of subcutaneous tissue leads to wrinkles

• Decreased numbers of melanocytes and Langerhans’ cells increase the risk of skin cancer


Age-related changes

Epidermal changes

•Thinner

•Permeability of the surface cells increased

•Larger melanocytes and grouped together; dark pigment plaques (age spots)

•Decrease in the number of immune cells in skin with aging


Age-related changes Dermal Changes

• Number of fibroblast and fibers is reduced

• Thin and somewhat translucent

• Elastic fibers become less resilient

• Slight calcification & formation of cross-links

• Reduce in numbers and gradual atrophy of sweat & sebaceous gland

• temp. regulation problem slow in growth of fingernails

• General loss of body hair

• Reduction of pigment in the hair with aging (heredity factors)

• Changes in dermal sensory receptor (pain, temp, touch, etc)


Age-related changesHypodermal changes (subcutaneous tissue)

• General loss of fat (most obvious in face and limbs)

•Cause of wrinkles

• Loss of padding reduction in blood supply to the skin pressure sores when bedridden

• Temperature regulation (older individuals feel chilly most of the time)

Modern Maturity Magazine “old age is when, upon getting out of the bathtub, you notice

that the full-length mirror is steamed up

– and you are glad of it”


Age-related DysfunctionsLentigo: after 50, dark-brown irregular areas, increased melanin, no tendency to malignancy

Senile Purpura: irregularly shaped purple patches, forearm and back of hands, minimal

Senile Angiomas: 75% over 70, elevated clusters of dilated capillaries, red spot,

Acrochordon: small pendulous skin growth (cutaneous tags)(cutaneous tags),, chest, neck, eyelids

Senile pruritus: loss of water, oil-secreting sebaceous glands, sweat glands, cracks (itching)(itching) Senile keratosis: (actinic keratosis) actinic keratosis) localized red areas of skin, soft-thicken-scaly-yellow brown

precancerousprecancerous

Seborrheic keratosis: formation of benign epidermal tumors, no precancerous, face, chest, back

Herpes Zoster: viral disease, shingles, same virus that causes small-pox, attacks sensory nerve

Decubitus Ulcers: pressure sores cavities of dead tissue form in skin, bedridden or immobilized

Skin cancer: malignant vs. benign, metastasize, early detection, melanoma vs. non-melanoma

Basal cell carcinoma: most commonmost common, from cells in deepest or basal layer of epidermis

Squamous cell carcinoma: develops from squamous EP, less common than basal, malignant

Malignant melanoma: highly malignant, potentially dangerous, usually develops in melaninsmelanins

Secondary skin cancer: originate in other areas of the body

biology of human aging

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