integumentary system. facts about your skin inegument = means covering integumentary system- skin,...
TRANSCRIPT
Facts about your Skin
• Inegument = means covering
• Integumentary System- skin, nails, hair, membranes, sweat, & oil glands
• Surface Area = 1.2 to 2.2 square meters• Weight = 4 to 5 kg• Thickness 1.5 - 4.0 mm • 7% of average body weight for an adult
Functions of Skin Protection
Cushions and insulates and is waterproof Protects from chemicals, heat, cold
Not helpful against organic solvents, heavy metals or plant
oils from poison oak Screens UV Acid Mantel keeps down bacteria ~pH 5 Macrophages gobble up invaders
Synthesizes vitamin D with UV
Functions of the Skin
Regulates body heat Sweat 500ml a day if about 31-32 C vessel dilate & constrict
Prevents unnecessary water loss But Lipid soluble – Vitamins and steroids in
Sensory reception (nerve endings)ThermoreceptorsPacinian receptors
• Bumps and deep pressure
Meissner’s corpuscles & Merkel disks• Aware of caress of clothing
1) Epidermis
• Epi = Upon• Keratinized stratified squamous epithelium
• nutrients reach by diffusion/ avascular
• Outer layer of dead skin cells called cuticle with living level underneath
. “Ashiness” is caused by this layer of dead skin cells being very
rough and raggedy
• DUST you see around is made up of dead skin cells!
Remember…
• Four basic types of tissue
– Epithelium – epidermis just discussed
– Connective tissue - dermis
– Muscle tissue
– Nervous tissue
2) DERMIS
Thick, tough, leathery, flexible layer Made of connective tissueVascularized – contains blood vesselsAnchors the epidermisCritical in Temperature regulation – contract and expand
In the dermis:• Oil glands• Sweat glands• Hair follicles• Fat tissue• Nerves• Connective tissue• Blood vessels
Tw
o layers P
apillary – areolar connective tissue; includes dermal
papillae R
eticular – “rticulum” (netw
ork) of collagen and reticular fibers
Fingerprints, palmprints, footprints
Dermal papillae lie atop dermal ridges Elevate the overlying epidermis into epidermal ridges Are “sweat films” because of sweat pores Genetically determined
Flexion creases• Deep dermis from continual folding
3) HYPODERMIS
• Subcutaneous Tissue /Hypodermis / superficial fascia– not really part of skin, but helps with protective
functions– superficial to connective tissue around bones– loose enough for free movement– Adipose tissue – different patters of accumulation for
men and women (grows when we gain weight)– shock absorber & insulator– Deep pressure receptors
Cells of the Epidermis
• Keratinized stratified squamous epithelium
• Four distinct cell types – Keratinocytes
– Melanocytes
– Merkel Cells
– Langerhans’/ Epidermal Dendrite Cells
Keratinocytes
o Most epidermal / superficial cellso Produce keratin – “kera”= horn . Fibrous protein
that gives stretcho Constantly in mitosis & pushed upwardso By the time they are on the surface they are deado New epidermis every 25-45 dayso Friction= keratin formation is accelerated
therefore callus- a thickening of the epidermis
Melanocytes o Spider shaped epithelial
cells that make Melanino Deepest layers of the
epidermiso Melanin made & collects
in granules called melanosomes
o Actin filaments move them along till they are taken up by Keratinocytes
o Granules accumulate on the superficial “sunny side” of the Keratinocytes nuclei & protect nucleus from harmful UV rays
Langerhans’ Cells / Epidermal Dendrite Cells
Macrophages (pac mans) that help activate our immune system
Layers of the Epidermis
• Thick skin= covers palms, fingertips, and soles of the feet– FIVE layers/ strata
• Thin Skin= rest of the body– FOUR layers (no
stratum lucidum)
Deep to Superficial:
stratum basalstratum spinosumstrata granulosumstrata lucidum strata corneum
Stratum basale/ stratum germinativum/ Basal Layer
– Deepest epidermal layer– Single row of cells– Attached to dermis w/ a wavy boarder line– 10-25% of cells are melanocytes & their
branches– undergoing mitosis
strata granulosum/ Granular Layer
• 3-5 cell layer
• keratinocyets flatten & start to die– not enough oxygen and nutrients b/c pushed
away from blood source
strata lucidum/ Clear Layer
o thin translucent band
o only in thick skin
o start making distinct layer
strata corneum/ Horny Layer
• 20-30 cells thick• ¾ of epidermal thickness• thickened plasma membrane of cells protects
from abrasion & penetration• glycolipid acts as a “water proof”• protects body from heat and water loss• “dandruff” 18kg= 40 lbs in a lifetime
Skin Color
1. Melanin• same # of melanocytes
• kind + amount of melanin made & retained– Darker = more darker melanosomes & retain longer
• Freckles & pigment moles are accumulation of melanin
• Sunlight causes melanin buildup– to protect from UV
Skin Color
2. Carotene– Yellow-orange pigment
– Accumulate in the stratum corneum
– Palms of hands, soles of feet
– Eat lots of rich carotene foods- becomes more obvious
3. Hemoglobin– Pinkish hue of light skin b/c can be seen through light
skin
Skin Appendages
• Derived from epidermis but extend into dermis
• Include– Hair and hair follicles– Sebaceous (oil) glands– Sweat (sudoiferous)
glands– Nails
HAIR
• Hair growth: averages 2 mm/week– Active & Resting phase then Shed– At the base of the follicle, hair papilla
• Contains blood vessels and nerves
Bulb• Contains matrix – epithelial cells responsible for
growth
– Contains melanocytes
• Functions of hair– Warmth – Sense light touch of the skin– Protection – scalp
• Hair color– Amount of melanin for black or brown; distinct form of
melanin for red– White: decreased melanin and air bubbles in the medulla– Genetically determined though influenced by hormones
and environment
Hair and hair follicles: complexDerived from epidermis and dermis
Everywhere but palms, soles, nipples, parts of genitalia
*“arrector pili” is smooth muscle*
Hair papilla is connective tissue________________
Hair bulb: epithelial cells surrounding papilla