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introduction to the integument
- · integument = skin
- - largerest organ (7%-8% of body weight)
- - 2 layers
- -epidermis
- - dermis
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epidermis
· superficial layer of stratified squamous epithelium
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dermis
- · deeper layer of areolar and dense irregular connective tissue
- - hypodermis: (not par of the skin) lies under the dermis, mostly adipose connective tissue
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integument functions
- · protection => infection/loss of fluids
- · prevention of H2O loss
- · temperature regulation
- · metabolic regulation
- · immune regulation
- · sensory reception
- · excretion/secretion
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the epidermis
- · most superficial layer
- · avascular
- · keratinzed stratified squamous epithelium
- - keratin is a water-insoluble protein
- - 4 to 5 layers (strata) of distinct cell type
- - thin skin: has 4 layers
- - thick skin: has 5 layers
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epidermal strata
- · from deep the superficial (as they grow)
- - stratum basale
- - stratum spinosum
- - stratum granulosm
- - stratum lucidium ( found only in thick skin)
- - stratum corneum
come lets get sun burn
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stratum basale
- · only layer that undergoes mitosis
- · one layer of cells adjacent to the dermis
- - keratinocytes: most abundant; produce keratin to waterproof skin
- - melanocytes: cell with long, branched cytoplasmic processes; produce a pigment ( black, brown, yellow) that absorbs UV light to prevent DNA damage, reducing some forms of skin cancer
- - tactile (Merkel) cells: sense touch
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stratum spinosum
- · several layers thick
- · daughter cells from the stratum basale
- - differentiate into non-dividing (may see a rare mitotic cell), highly specialized keratinocytes
- · epidermal dendritic cells
- - phagocytes that engulf invading pathogens
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stratum granulosum
- ·3-5 layers of keratinocytes
- - cytoplasm fills with keratin/keratohyalin filaments
- - organelle begin to degrade
- - fully keratinized cells are dead but strong and water-insoluble
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stratum lucidum
- · thin, translucent region, 2-3 layers thick
- · present only in thick skin such as sole of feet and palms of hands
- ·cells lack organelles, filled with eleidin
- - transparent, intermediate product of keratin maturation
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Stratum corneum
- · most superficial layer of epidermis
- · thickness varies from few to 30 layers thick depending on location on the body
- · comprised solely if dead keratinocytes
- -sloughed off by abrasion=dust
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epidermal variation: skin color
- skin color is determines by 3 pigments
- · hemoglobin: blood pigment; causes light complexions to look pink ( or blue)
- · melanin: pigment produced by melanocytes; increase in people exposed to more UV light
- ·Carotene: yellow-orange pigment from food that builds up in the skin
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epidermal variation: skin marking
- · nevus:localized overgrowth of melanocytes
- a.k.a. mole
- ·hemangioma : proliferation of blood vessels
- - may disappear (strawberry) in childhood or may persist (port-wine) though adulthood
- · friction ridges: fold of epidermis/dermis on fingers, palms, soles, and toes for grasping
- - cause us to leave fingerprints
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the dermis
- · lies deep to the epidermis
- · 2 layers of connective tissue
- -papillary: superficial
- - reticular: deeper
- - manly collagen fibers
- - contains blood vessels, glands ,hair follicles, nail roots, sensory nerve endings and smooth muscles
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the papillary layer
- · directly below stratum basale cells of epidermis
- - dermal papillae and epidermal ridges interlock, increasing the surface area between epidermis and dermis
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the reticular layer
- · forms majority of the dermis
- · comprised manly of dense irregular connective tissue with large bundles if collagen fibers, blood vessels, glands, hair follicles and nerves
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lines of cleavage
- · lines in the deep dermis formed by the orientation of collagen bundles
- important to surgeons: incisions across these lines heal more slowly that incisions along the lines
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innervation
- · nerve fibers are present in dermis
- · functions:
- - tactile (touch) receptors
- - control blood flow
- - control glandular secretion
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blood supply
- · epidermis: avascular
- · dermis: contains blood vessels
- - important in controlling body temperature
- vasoconstriction: narrowing blood vessels preserves core body heat
- - vasodilation: widening blood vessels releases body heat, lowering body temperature
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the hypodermis
- ·aka subcutaneous layer
- - deep to, not really part of, the integument
- - areolar and adipose connective tissues
- · functions:
- - protects underlying structures
- - stores energy
- - thermal insulation
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epidermal derivatives
- · structure that grow form the epidermis
- - nails
- - hairs
- - glands
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nails
- · derived form the stratum corneum
- · cells densely packed together filled with parallel fibers of hard keratin
- · the nail plate has whitish free edge, a pinkish nail body and a nail root
- ·the nail body cover a layer of epidermis called the nail bed
- · the nail bed appear pink because of the underlying capillaries
- ·protective structure on digits
- · parts
- - nail body: flat keratinized cells protecting digit
- - nail bed (hyponychium): live epidermal cells under nail body
- - nail root: region hidden by cuticle
- -nail matrix: thickened growing part if the nail bed
- - lunula: white semilunar proximal area of the nail body caused by thickened underlying stratum basale obscuring capillaries in dermis
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hair
- · columns of keratinocytes growing form follicles deep in dermis or hypodermis
- · regions of a hair from deep to surface
- - hair bulb
- - hair root
- - hair shaft
- ·also called a pilus
- · fragment of keratinized cells
- · grows from oblique tube called a hair follicle
- · grows almost everywhere, except
- - lips
- - nipples
- - parts of genitals
- - palms and soles
- - ventral and lateral surface of fingers and toes
- - distal segments of fingers
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3 types of hair
- · lanugo: fine downy unpigmented hair of fetus
- · velius:
- - fine unpigmented
- - 2/3 hair of women
- - 1/10 hair of men
- - all of children's except eyebrows, eyelashes, and scalp
- ·terminal:
- - course and pigmented
- - eye brows, eyelashes and scalp
- - after puberty
- - axillary
- - pubic
- - male facial hair
- - some hair of trunk and limbs
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hair structure
- · from deep to superficial
- - hair papilla: connective tissue, nerves and blood vessels below follicle that support the keratinocytes
- - hair bulb: a swelling at bottom of follicle filled with dividing keratinocytes, increase in hair matrix causing hair growth
- - arrector pili: involuntary smooth muscle attached to hair shaft, responds to emotional states (fear or rage) and cold temperature by contracting standing hair up and producing "goose bumps"
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functions of hair
- ·protection
- · heat retention
- · facial expression
- · sensory reception
- · visual identification
- · chemical signal dispersal
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skin exocrine glands
- · 2 most common types:
- - sweat glands: produce watery solution
- - merocrine and apocrine (genital/armpit)
- - sebaceous glands: produce oily secretions (halocrine gland => mostly associated with hair
- · 2 rare types
- - ceruminous gland: produce ear wax
- - mammary gland: produce milk
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merocrine sweat glands
- ·simple coiled tubular glands that secret into adduct with a pore on skin's surface
- - secretion is 99% H2O, clear, and controlled by nervous system
- - numerous on forehead, palm, and soles
- · functions
- - thermoregulation
- - secretion
- - protection
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apocrine sweat glands
- · siple coiled tubular glands that secret into hair follicles around nipple (areolae) armpit (axillae) groin (public) and anus( anal)
- -secretion is thick, cloudy, protein and lipids
- - leads to bacterial growth, causing body odor in the above regions
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sebaceous glands
- · secrete oily sebum into hair follicles
- - lubricates hair and skin
- - relatively inactive during childhood; sex hormones at puberty cause secretion to increase significantly
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basal cell carcinoma
- · most common
- · least dangerous: hardly metastasizes
- · arises in stratum basale and invades dermis
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squamous cell carcinoms
- ·arises from keratinocytes of stratum spinosum
- · can metastasize to lymph nodes
- · can be lethel
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malignant melanoma
- · most deadly but only 5% of cases
- ·arises from melanocyte of existing mole
- · metastasizes quickly and often fatal if not treated quickly
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1st degree burn
(partial- thickness burn)
- ·only dermis
- ·usually localized
- · redness, slight edema and pain
- · sunburn
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2nd degree burn
( partial-thickness burn)
- · epidermis and part if dermis
- · red, tan, white
- · blistered and painful
- · may cause damage to hair follicles, nerve endings and cutaneous glands
- ·sunburn and scalds
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3rd degree burn
(full-thickness burn)
- ·epidermis and dermis are completely destroyed
- · contracture and disfigurement can result
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