integumentary system
Post on 02-Jan-2016
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Skin Functions• Physical barrier
• General senses: touch, pressure, pain, temperature
• Vitamin D source
• Temperature regulation
• Excretion of wastes
Types of cells: • Keratinocytes
– produce keratin
– totally replaces epidermis every 25-45 days
• Melanocytes– produce melanin
• Langerhans– dermal macrophages
• Merkel cells– sensory receptors for touch
Skin Layers
• Epidermis - Stratified squamous epithelium that is keratinized
• Dermis - Irregular dense fibrous connective tissue
Major Layers of Skin
• Epidermis
– stratum corneum
• outermost
• thickest
• dead, flaky, dandruff
– stratum lucidum
• (clear)
– stratum granulosum
• increased keratinization
Major Layers of Skin
• Epidermis
–stratum spinosum• (prickly layer)
–stratum basale • (stratum
germinativum)
• mitotic division
• Contains melanocytes
Skin Layers
• Dermis
– Papillary layer contains:
• Dermal papillae
• Meissner’s corpuscles (touch receptors)
– Reticular layer
• Arteries
• Veins
• Glands
• Pacinian corpuscles (pressure receptors)
Skin Color• Melanin
– Yellowish to reddish-brown to black
– Racial differences result from kind and amount of melanin
– Freckles: local accumulation of melanin
– Melanin increase due to damage from ultraviolet radiation
• Excessive exposure to sun damages elastin fibers, depresses immune system, and alters DNA possibly leading to skin cancer
Color variations
– Redness (Erythema)• blushing, fever, inflammation, allergy
– Pallor• fear, anger, stress, anemia
– Jaundice• yellowish color due to bile; liver disorder
– Bronzing• Addison’s disease ; adrenal cortex disorder
– Bruises (hematoma)• clotted blood beneath skin
Accessory Structures
• Sudoriferous (Sweat) Glands–Eccrine glands
•covers most of body; especially hands, feet, and head
•Eccrine secretion contains water, salts, vitamin C, antibodies, waste (urea, uric acid, ammonia), and lactic acid
Accessory Structures
• Sudoriferous (Sweat) Glands–Apocrine glands (axial and genital
areas)• Apocrine secretions add fatty substances and proteins
• Breakdown of aprocrine secretions by bacteria causes body odor
• Begin functioning at puberty
Accessory Structures
• Specialized Sudoriferous (Sweat) Glands–Ceruminous glands
- secrete wax
–Mammary glands - secrete milk instead of sweat
• Sebaceous (Oil) Glands
– Secrete sebum
• softens and lubricates skin and hair
• waterproofs
• activated by hormones during puberty
– Whitehead - gland blocked by accumulated sebum
– Blackhead - dried, oxidized sebum
– Acne - active inflammation of sebaceous glands
– Seborrhea (Cradle cap) - overactive sebaceous glands
Hair & Hair Follicles
– Structure of hair• Shaft - projects from
skin
• Root - embedded in skin
• 3 layers of ketatinized cells
– medulla - core– cortex - surrounds core– cuticle - outermost
layer
Hair & Hair Follicles
– Structure of follicle
• Hair bulb - expanded end of follicle
• Hair papilla - dermal papilla protruding into hair bulb; supplies nutrients; stimulates growth
• Hair matrix - produces hair; active division; older cells pushed to top, increase keratinization & die
• Arrector pili -muscle that raises hairs; causes goose bumps
Distribution, Types, & Growth of Hair
• Vellus - fine body hair of children and females• Terminal - coarse hair of scalp and eyebrows• Growth stimulated by androgens• Affected by nutrition• Average growth rate = 2mm per week• Hair Cycles vary
– scalp follicles active approx. 4 yrs– eyebrow follicles active 3-4 months
Hair Thinning & Baldness
–After 40’s resting cycles lengthen
–Hair not replaced as fast as lost
–Baldness = alopecia
• Male Pattern Baldness
–Genetically determined
–Sex influenced
Nails• Scale-like modifications of epidermis
• Structure
– Free Edge
– Body
– Root
– Nail Bed - epidermis beneath nail body
– Nail Matrix - proximal portion of nail bed
– Lunula– Nail folds
– Eponychium (cuticle)
Skin Disorders• Warts - nonmalignant epithelial growth caused by a
virus
• Cold sores (fever blisters)
– small fluid-filled blisters around lips & mouth
– caused by a herpes simplex virus
• Acne - inflammation of sebaceous glands
• Impetigo - inflamed lesions caused by staphylococcus infection
• Decubitus ulcers (bed sores) caused by irritation and inadequate circulation
Skin cancers• Most skin tumors benign (ex. Warts)
• Basal Cell Carcinoma– least malignant
– approx. 30% of caucasians will develop this
– 99% cure rate
• Squamous Cell Carcinoma
– Scaly elevation arising from the stratum spinosum
Cutaneous melanoma• Arise from melanocytes• 2 types
– melanocarcinoma– malignant melanoma
• Irregular growths with variety of pigmentation (brown, gray, black, or blue)
• Occur in all age groups, usually in people who sunburn easily
• More common in people who get short intense exposure to sunlight.
• Survival rate is low.• May begin in regular skin or mole
Classification of Burns
• First-degree burns - involves only epidermis
• Second-degree burns - involves both epidermis and dermis
• Third-degree burns - complete destruction of both layers, probable involvement of subcutaneous tissue
• Burns also classified by the extent of burn area
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