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Integumentary System- Emerson Brown; Per. 4 (Layers (5) of Epidermis…
Integumentary System- Emerson Brown; Per. 4
Function of the Integumentary System
Protection
skin is vulnerable to microorganisms, abrasions, temp. extremes, harmful chemicals; UV radiation
three types of barriers
Chemical Barriers
skin secretes melanin
melanin provides a protective shield
skin cells secrete defensins
Physical Barriers
barrier capacity arises from stratum corneum
glycolipids
mortar
Biological Barriers
composed of dentric cells of epidermis and macrophages
dentric cells: apart of immune system by engulfing foreign invaders
dispose of viruses and bacteria
Cutaneous Sensation
cutaneous sensory receptors: apart of nervous system
exteroceptors: a sensory receptor which receives external stimuli
stimuli arising outside the body:
lamellar: corpuscles alert us to bumps or contacts
Hair follicle receptors: report wind blowing
tactile: allows us to feel objects (clothing against skin)
Free nerve endings: senses painful stimuli (chemicals, heat, cold)
Metabolic Functions
when sun bombards skin, cholesterol molecules are converted to vitamin D precursor; calcium cannot be absorbed without vitamin D
"disarms" many cancer causing chemicals
activates steroid hormones
Blood Reservior
vascular supply can hold about 5% of body's blood volume
nervous system constricts dermal blood vessels
Excretion
body eliminates nitrogen-containing wastes (ammonia, urea, + uric sweat)
wastes are excreted through urine
profuse sweating is an important avenue water and salt loss
Body Membranes
cutaneous
organ system composed of keratinized stratified squamous epithelium (epidermis) firmly attached to a thick layer of connective tissue (dermis)
dry membrane
exposed to air and elements (unlike other body membranes)
mucous "mucosae"
line all body cavities that open to the outside of the body
digestive, respiratory, and urogenital tracts
moist membranes bathed by secretion
lamina propia: epithelial sheet lies directly over a layer of areolar connective tissue
adapted for absorption and secretion
many secrete mucous (ex. digestive and respiratory tracts secrete mucus, but that of the urinary tract doesn't
serous (serosae)
two layers: parietal and visceral: in between the two lies cavities and serous fluid
thin membranes which cover walls
pleurae: line the thoracic wall and cover the lungs
pericardium: encloses the heart
peritoneum: encloses the abdominopelvic viscera
Layers (5) of Epidermis
stratum basale: attached to dermis, single row of cells; rapid division
stratum spinosum (prickly): several layers; does not exist in living cells
stratum granulosum: consists of one to five cell layers; process of keratinization occurs
stratum lucidum: smooth, seemingly translucent layer of the epidermis; dead flattened
stratum corneum: the horny, outer layer of skin
epidermis: four cell types and five distinct layers
keratinocytes: produce keartin; tied together by derosomes; fpund in stratum basale; dead by the time they reach the skin surface
callus: thickening of dermis
melanocytes: spider-shaped epithelial cells; produces melanin and found in deepest layer.
Dendritic cells: arise from bone marrow and migrate to epidermis; ingest foreign substances; extends among surrounding keratinocytes
Tactile Epithelial: present at epidermal-dermal junction; associated with a dislike nerve ending
Skin Cancers: most common type of cancer; most important risk factor is UV radiation
Basal Cell Carcinoma
least malignant and most common
accounts for 80% of cancers
cells proliferate and invade dermis
Squamous cell carcinoma
Second most common type of skin cancer
arises from Keratinocytes
appears as a reddened papule on head, scalp, ears, lip, hands
Melanoma
cancer of melanocytes; most dangerous
1/3 develops from pre-existing moles
key to survival is detection
Layers of Dermis: strong, connective tissue
Cells: fibroblast, macrophages, mast, white blood cells,
Function: binds body together; two layers
Papillary
aerolar connective tissue; collagen and elastic fibers
allows phagocytes to wander freely as they patrol for bacteria
dermal papille: indent overlaying epidermis; contains capillary loops
friction ridges: enhances ability to grip
Reticular
80% of thickness of dermis
dense irregular connective tissue
dermal vascular plexus: network of blood vessels
cleavage (tension) lines: formed by separations; run longitudinally in skin of limbs and circular around neck and trunk
flexure lines: dermal folds (occur near joints; dermis is tightly secured to deeper structures
dermis folds and deep skin creases (visible on wrists, fingers, soles, and toes
Accessory Organs
Hair
Vellus hair: children and adult female hair; pale and fine
Terminal hair: coarse, long hair; eyebrows, scalp, etc.
appears in axillary region, chest and face of men
hair grows of 2mm per week
male pattern baldness: most common type of baldness
follicles respond to androgens with shorter growth cycles
Nails: forms a clear protective coating on the dorsal surface; "tools" to pick up objects
nail matrix: responsible for nail growth; thickened proximal portion of nail body
lunule: "little moon"; white crescent matrix part of nail
nail folds: proximal nail fold projects onto the nail body
hyponychium: area below the nail
Glands
sweat glands (sudoriferous): distributed all over body (except nipples and genetaila); up to 3 million per person; two types
Eccrine Sweat glands
palms, feet, forehead
tubular glands
produces sweat and filtrates blood (sweat is 99% water and 1% salt
prevents body from overheating
heat sweating begins in forehead; emotional sweat begins on palms, soles, and axillary region
Apocrine glands
lies deep within dermis; ducts empty into hair
begins at puberty, may be the human's version of animal sexual scent glands
two types: ceruminous and mammary
Sebaceous glands: oil glands, alveolar glands
secrete sebum
cells accumulate oily lipids until they become too engorged and burst
develop as outgrowths of hair follicles
sebum softens and lubricates hair and skin
Infections
infection is common after skin is burned and it is important for doctors to prevent it
widespread bacterial infection is the leading cause of death in burn victims
skin graft helps prevent mass infection
Burns: tissue damage enflicted by heat, electricity, radiation, etc. (can lead to renal failure or circulatory shock)
First Degree
only epidermis is damaged
redness, swelling, pain
takes two to three days to heal
Second Degree
damages epidermis and upper region of dermis
causes blistering; partial thickness burn
three to four weeks to heal
Third Degree
full-thickness burn
nerves are destroyed
critical if 10% of body is third degree burns
rule of nines: a method of computing the extent of burns
Treatment
requires the replenishment of calories through nutrients
preventing infection
removal of burned skin with the replacement of healthy tissue
