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Chapter 5: Integumentary System (5.10 - Effects of Aging (Skin injuries…
Chapter 5: Integumentary System
Introduction
Cutaneous Membrane
epidermis
top layer of skin
dermis
under epidermis
Accessory Structures
hair, nails, exocrine glands
5 Major Functions of the Integument
protection
protects from impacts, chemicals, and infections
temperature maintenance
regulates heat exchange with the environment
synthesis and storage of nutrients
synthesizes vitamin D
sensory reception
detect touch, pressure, pain, and temperature stimuli; relay info to nervous system
excretion and secretion
excrete salt, water, organic wastes, and sometimes milk
5.1 - Epidermal Strata
Thick Skin
5 layers
found on palms and soles of feet
stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale
Thin Skin
4 layers
found on the rest of the body
Stratum Germinativum/Basale
forms epidermal ridges
firmly attached to basement membrane
dermal papillae extend upwards between adjacent ridges; forms fingerprints
germinative cells dominate stratum germinativum - new cells are generated
melanocytes synthesize melanin
Intermediate Strata
Stratum Spinosum (Spiny Layer)
cell continues to divide and add to thickness of the epithelium in this layer
Stratum Granulosum (Grainy Layer)
contains cells displaced from spinosum; cells stop dividing and begin to make keratin
Stratum Lucidum (Clear Layer)
covers granulosum; cells are flattened, densely packed, and filled with keratin
Stratum Corneum
most superficial layer; has 15-30 layers dead epithelial cells that have accumulated large amounts of keratin
cells are "keratinized" or "cornified"; packed tightly together by desmosomes
takes 2-4 weeks for cell to move from germinativum to corneum
5.2 - Factors of Skin Color
Role of Pigmentation
Carotene
orange-yellow pigment
present in orange vegetables
eating large amounts can turn skin orange
can be converted to Vitamin A
Melanin
yellow-brown pigment produced my melanocytes
Melanocytes manufacture/store melanin within vesicles
absorbs UV radiation from sun before it destroys DNA
Dermal Circulation
if vessels in skin dilate, red tones are more pronounced because the vessels widen so the skin can lose heat
blood with abundant oxygen is bright red
when vessels are constricted, skin becomes pale because the blood will lose oxygen and become darker
cyanosis - bluish coloration of the skin; response to extreme cold or circulatory issues
5.3 - Effects of Sunlight on Skin
Benefits
Vitamin D3 is released by liver and then converted into calcitriol by the kidneys (hormone essential to absorption of calcium and phosphorus)
Detrimental
Basal Cell Carcinoma - most common skin cancer; originates in stratum germinativum
Squamous Cell Carcinoma: less common; involves superficial layers
Malignant Melanoma: extremely dangerous; usually forms from moles; melanocytes grow rapidly and mastasize throughout lympohoid system
5.4 - Dermis
Papillary Layer
consists of loose connective tissue that supports epidermis
contains capillaries and nerves supplying the surface of the skin
Reticular Layer
interwoven meshwork of dense irregular connective tissue
contains elastic fibers and collagen fibers
also includes hair follicles, sweat glands, blood vessels, lymphatic vessels, and nerve fibers
5.5 - Hypodermis/Subcutaneous Layer
contains loose connective tissue with many fat cells
fat serves as energy reserve and shock absorber
men accumulate fat at neck, upper arms, lower back, and over buttocks during puberty
women accumulate fat in the breasts, buttocks, hips, and thighs during puberty
subcutaneous injections are used because the hypodermis contains no vital organs and few capillaries
5.7 - Sebaceous Glands and Sweat Glands
Sebaceous (Oil) Glands
holocrine glands that secrete oily lipids into hair follicles or skin
involves rupture and death of cells
contraction of arrector pili muscle squeezes gland, causing the secretion
Sebum - lubricates hair and skin, inhibits growth of bacteria
Sebaceous Follicles - large sebaceous glands that secrete sebum directly onto skin (locations: face, back, chest, nipples, external genitalia)
Acne - glands become blocked and build up of secretion causes inflammation to occur
Sweat Glands
Apocrine
occurs during puberty; odorous
secretes around nipples, armpits, and groin
secretes into hair follicles
Merocrine
secretes onto skin
born with them
99% water, also contains electrolytes, organic nutrients, and waste
sodium chloride makes it salty
5.6 - Hair
Structure of Hair/Hair Follicles
Hair follicle projects deep into dermis
hair papilla - connective tissue containing capillaries/nerves
Hair root - anchors hair into skin
Hair shaft - part we see on surface
cuticle - made of overlapping shingle layer cells
cortex - underlying layer
medulla - core of the hair
Functions of Hair
protect scalp from UV light
cushion head from soft blows
insulating benefits for skull
prevent entry of foreign particles in nose and eyes
early warning system to prevent injury (nerve fibers at base of follicles)
Hair Color
determined by amount of pigment produced by melanocytes
genetically determined, but environmental factors can influence
color lightens with age; white hair results from lack of pigment and/or air bubbles in shaft
5.8 - Nails
Nail bed - body of the nail
Nail root - nail production occurs; not visible from surface
Cuticle - portion of the stratum corneum that extends over exposed nail
Lunula - pale crescent near root; not pink like rest of nail because no blood vessels
5.9 - Repairing Integument After Injury
Step 1
: scab forms; restores epidermis; restricts entry of microorganisms
Step 2
: Clot consists of fibrin (forms blood proteins); cells of germinativum divide and replace missing epidermal cells; macrophages clear area of debris; granulation tissue
Step 3
: Fibroblast activity formed meshwork of collagen fibers
Step 4
: Scar tissue takes over
Burns
First Degree
killed: superficial cells of epidermis
injured: deeper layers of epidermis, papillary dermis
inflamed and tender
Second Degree
killed: superficial layers of epidermis, sometimes dermis
injured: reticular layers in dermis, accessory structures
not affected
blisters and very painful
Third Degree
killed: all epidermal and dermal cells
injured: deeper tissues, organs, and hypodermis
charred and no sensations felt
5.10 - Effects of Aging
Skin injuries and infections are more common
Sensitivity of immune system is reduced
Weaker muscles and bones
Higher sensitivity to the sun
Skin becomes dry and scaly
Hair thins and changes color
Wrinkly and saggy skin
Ability to lose heat decreases
Slow skin repairs
5.11 - Protection
protects from dehydration, environmental chemicals, and impacts