Transcript instructions on the - Middle Tennessee State University

Integumentary System
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Epidermis and dermis
Hypodermis
Thick and thin skin
Skin color
Functions of the skin
Hair and nails
Cutaneous glands
Overview of the Skin
• Largest organ of the body (16% of body weight)
• Two layers
– epidermis
• Keratinized __________________________ epithelium
• contains ______________
– dermis
• connective tissue layer
• Rests on subcutaneous layer or hypodermis
• Normal thickness of 0.5 mm, up to 5 mm
Cell Types & Layers of the Epidermis
Stratum basale
Dermis
• Thicker than epidermis
• Composition
– collagen, elastic & reticular fibers, fibroblasts &
accessory structures such as hair follicles and glands
• Dermal papillae
• Layers
– papillary layer
– reticular layer
Layers of the Dermis
Hypodermis
• Known as subcutaneous
tissue or superficial fascia
• Has more adipose than
dermis
• Functions
– ______________________
– ______________________
Hypodermis
Skin Colors (Pigmentation)
• ________________ is red pigment of red blood cells
– visible through dermal collagen fibers
• ________ is yellow pigment of vegetables & egg yolks
– concentrates in stratum corneum & subcutaneous fat
• Melanin pigment produced by ___________________
– pigment synthesis stimulated by UV radiation from
sunlight
– produces yellow, brown, black and reddish hues
Abnormal Skin Colors
• Cyanosis - blueness from lack of ____________
• Erythema - redness from dilated cutaneous
vessels
• Jaundice - yellowing of skin & sclera - bilirubin
• Bronzing - golden-brown color of Addison
disease (deficiency of glucocorticoid hormone)
• Pallor - pale color from lack of blood flow
• Albinism - a genetic lack of melanin
• Hematoma - a bruise (visible clotted blood)
Skin Markings
• Birthmarks
– Hemangiomas (strawberry marks)
– Port-wine marks
– (discolored skin, malformations of dermal blood
capillaries)
– Café au lait spots
• Freckles & moles = aggregations of melanocytes
– freckles are flat; moles are elevated
• Epidermal ridges - leave oily fingerprints
Functions of the Skin
• Barrier = tough, dry, acid mantle, water barrier, UV barrier
• Vitamin D synthesis
– UV light converts 7-dehydrocholesterol in dermal vessels to vitamin D3
• Cutaneous absorption
– 1-2 % oxygen absorption by diffusion through skin
– fat-soluble vitamins (A, D, E & K) easily absorbed
• Sensory functions
– receptors for heat, cold, touch, pressure, vibration & pain
• Thermoregulation
– cutaneous vasodilation & constriction and sweating
• Psychological and social functions
– appearance & social acceptance
– facial expression and nonverbal communication
Characteristics of Human Hair
• S. corneum of the skin contains soft keratin
• Hair and nails are composed of hard keratin
– toughened by disulfide bridges between molecules
• Hair found almost everywhere on the body
• 3 different body hair types
– lanugo -- fine, unpigmented fetal hair
– vellus -- fine, unpigmented hair
– terminal hair -- coarse, long, pigmented hair
Structure of Hair and Follicle
• Hair is a filament of keratinized cells
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Shaft: parts above skin
Root: parts below within follicle
Follicle: epidermal invagination into dermis
Cross section layers: medulla, cortex and cuticle
Bulb: swelling in base where hair originates
Papilla: vascular tissue in bulb
• Hair color is due to melanin pigments
– eumelanin
– pheomelanin (agouti signaling protein)
Structure of Hair Follicle
• Epithelial root sheath
is an extension of the
epidermis
• Connective tissue
root sheath is derived
from the dermis
• Hair receptors
entwine each follicle
• Arrector pili muscle
Growth of Hair
• Mitosis in stratum basale of epithelial root sheath
– as cells become keratinized they are pushed upward
• Grow 1 mm every 3 days
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Anagen (growth) phase lasts 6-8 years (scalp)
Catagen (degenerative) phase , growth stops, club hair, 2-3 wks
Telogen (resting) phase, 1-3 months
Anagen in eyelashes and eyebrows lasts about a month
• Alopecia
• Hirsutism
• Pattern baldness (sex influenced trait)
Functions of Hair
• Body hair too thin to provide warmth
• Sensory functions
– alert us to parasites crawling on skin
• Scalp hair provides heat retention & sunburn cover
• Sex and individual recognition
• Beard, pubic & axillary hair indicate sexual
maturity & help distribute sexual scents
• Guard hairs & eyelashes prevent foreign objects
from getting into nostrils, ear canals or eyes
• Expression of emotions with eyebrows
Nails
• Clear, hard derivative of stratum corneum
– densely packed cells filled with hard keratin
• Flat nails allow for fleshy, sensitive fingertips
• Growth rate is 1 mm per week
– new cells added by mitosis in the nail matrix
– nail plate is visible part of nail
Cutaneous Glands
• Sweat glands
– _______________
– _______________
• Sebaceous glands
• Ceruminous glands
• Mammary glands
Sweat Glands
• Filtrate of plasma
– 500 ml of perspiration/day
• Merocrine gland - simple
tubular gland
– millions of them
– cool the body
• Apocrine glands
– found only near hair follicles & respond to stress & sex
– body odor produced by _______________ action on fatty acids
Sebaceous Glands
• Oily secretion called ______________ that contains
broken-down cells
• Flask-shaped gland with duct that may open into hair
follicle
Ceruminous Glands
• Modified sweat gland
• Found only in external ear canal
• Their secretion combines with sebum to produce
earwax
– waterproof keeps eardrum flexible
Breasts and Mammary Glands
• Breasts of both sexes rarely contain glands
– Secondary sexual characteristic of females
– Glandular tissue - only during lactation and pregnancy
• modified apocrine sweat gland
• Mammary ridges or milk lines
Diseases of the Skin
• Most vulnerable organ to injury & disease
– skin diseases common in old age
• Skin cancer
– induced by UV rays of the sun
• most common in fair-skinned and elderly
– basal cell carcinoma
• arises from cells of the stratum basale
• treated by surgical removal & radiation?
– squamous cell carcinoma
• arises from keratinocytes in the stratum spinosum
• if neglected, metastasis to the lymph nodes can be lethal
– malignant melanoma (most deadly cancer)
• arises from melanocytes of a preexisting mole
• ABCDE--asymmetry, border irregular, color mixed, diameter
over 6 mm, & evolving
Some Skin Disorders
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See Table 6.3
Acne
Dermatitis
Eczema
Psoriasis
Rosacea
Seborrhea
Tinea
Burns
• Causes of burns -- hot water, sunlight, radiation, electric
shock or acids and bases
• Causes of deaths
– fluid loss, infection, & effects of dead tissue
• Degrees of burns
– 1st-degree = only the epidermis (red, painful & edema)
– 2nd-degree = epidermis & part of dermis (blistered)
• epidermis regenerates from hair follicles & sweat glands
– 3rd-degree = epidermis, dermis & more is destroyed
• often requires grafts & fibrosis may occur
• Treatment -- fluid replacement & infection control
Wound Healing of a Laceration
• Damaged vessels leak
blood
• Damaged cells & mast
cells leak histamine
– dilates blood vessels
– increases blood flow
– increases capillary
permeability
• Plasma seeps into wound
carrying antibodies,
clotting factors & WBCs
Wound Healing of a Laceration
• Clot forms
• Scab forms on
surface
• Macrophages start
to clean up debris
Wound Healing of a Laceration
• New capillaries grow
• Fibroblasts deposit
new collagen
• Fibroblastic phase
begins in 3-4 days &
lasts up to 2 weeks
Formation of granulation tissue.
Wound Healing of a Laceration
• Surface epithelial
cells multiply &
spread beneath scab
• Scab falls off
• Epithelium
regenerates
• Connective tissue
forms only scar
tissue (fibrosis)
• Remodeling phase
Epithelial regeneration & connective
may last 2 years
tissue fibrosis.