biology of human aging
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Biology of Human Aging. Chapter 4 The Integumentary System. Outline. Review of structure and Function Epidermis / Dermis 2. Age-related Changes Epidermal Changes Dermal Changes Hypodermal Changes 3. Age-Related Dysfunctions - PowerPoint PPT PresentationTRANSCRIPT
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Biology of Human Aging
Chapter 4
The Integumentary System
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
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
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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
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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)
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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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
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)
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Skin (Integument)
Figure 5.1
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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
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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
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Waterproofing
Protection from abrasion and penetration
Rendering the body relatively insensitive to biological, chemical, and physical assaults
Functions
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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
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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
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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
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Hypodermis
Subcutaneous layer deep to the skin
Composed of adipose and areolar connective tissue
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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
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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
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Sebaceous Glands
Simple alveolar glands found all over the body
Soften skin when stimulated by hormones
Secrete an oily secretion called sebum
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
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
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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
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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
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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
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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)
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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”
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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