One of the largest organs ~ 2/3 size of the liver Receives up to 1/3 of blood supply Layers epidermis Site of fluid accumulation in blisters Dermal papilla - nipple-shaped mound dermis hypodermis fascia or periosteum Functions 1. Physical protection from environmental hazards, influences, water, disease, chemicals 2. Protect from excessive water loss 3. Regulate body temperature 4. House sensory receptors 5. Excretion of waste materials 6. Synthesis of vitamin D3 7. Synthesis and storage of lipid reserves 8. Coordinate immune response to pathogens and cancers in skin Epidermis - Stratified squamous epithelium 0.1 to 1mm thick (due to pressure, rubbing and other mechanical factors palms of hands and soles of feet thick in the foetus Layers 1. Stratum germinativum - basal layer, cell division with many mitotic figures. Attach to basal lamina. Contain epidermal stem cells, melanocytes 1:4 - 1:20 ratio, and Merkel cells (Pressure sensitive, release chemicals to stimulate neurons when "pushed". Langerhans cells to initiate immune response against pathogens. 2. Stratum spinosum - cells pull apart, thin "spiny" interconnections, Keratinocytes are bound together by desmosomes attached to tonofibrils of the cytoskeleton 3. Stratum granulosum - Keratinocytes produce keratohyalin and keratin. Keratin fibers develop as cells become thinner and flatter. Gradually, the cell membranes thicken, the organelles disintegrate, and the cells die 4. Stratum lucidum - granules fuse, appears "glassy", cells become further elongated, nucleus shrinks. 5. Stratum corneum - no nucleus, keratin predominate, multiple layers of flattened, dead, interlocking keratinocytes, typically relatively dry, water-resistant, but not waterproof, permits a slow water loss by insensible perspiration. Skin color due to combination of blood supply, melanin, and carotene. Melanocytes stimulated by sun's UV light, causes tyrosinase to oxidize tyrosine to form melanin. Dermis - Consists of CT, collagen and elastic, BVs, 3 mm thick (soles of feet) 0.5 mm in the eyelid. Hypodermis - beneath dermis, CT varies in fat cell content, attachment to deeper layers. Eyelids -without hypodermis containing fat Fat content important in transplants. Hair 1. Vellus hairs - fine "peach fuzz" over much of body 2. Intermediate hairs - hairs of upper and lower limbs 3. Terminal hairs - heavy, pigmented, curley hairs of head Hair cycle Eyelash - 2 - 4 months Head - 2 - 5 year cycle Associated hair structures 1. Arrector pili muscle Straighten hair Squeeze ducts Cause goose pimples 2. Sebaceous glands - ducts into follicle Oily secretions for: Moistness Prevent heat loss Prevent excessive water loss Sudoriferous or eccrine sweat glands - none on lips, male penis, or nail bed. Simple tubular gland- enter at peak of ridge in hands and feet Myoepithelial cells - modified muscle cells adjacent to glands to help excrete fluid. Two million per person 700 - 900 ml per day (average) Apocrine - Axillae, nipple areolae, groin External auditory meatus - modified sweat glands - cerumen and lipid Mammary glands Eyelids - Moll's glands - open into follicles of eyelashes Sensory Receptors - Receptive Fields Free nerve endings - pain, temperature, and hairs Merkel's (tactile) disk - fine touch s. germinativum Miesner's corpuscles - Light touch d. papilla Ruffini corpuscles - Skin pressure/distortion End Bulbs of Kraus - cold Pacinian corpuscles - deep pressure Nails 1. Nail bed 2. Nail wall - skin around the nail 3. Nail groole - between skin and the nail, eponychium and hyponychium 4. Nail - tightly packed keritinized epithelial cells, have higher sulfur content 5. Lunula - white of nail/growth point. - 1 mm/week
First Degree - Epidermis Second Degree - Dermis Third Degree - Epidermis and Dermis Growth Sides Germinal Structures Transplants Rule of Nines 9 % each Head Right anterior trunk Left anterior trunk Right posterior trunk Left posterior trunk Arm Anterior leg Posterior leg 1 % - Inguinal region
1. Blood clotting 2. Vasodilation 3. Macrophage migration 4. Debris removal 5. Fresh capillary buds 6. Migration of Fibroblasts Blood vessels CT formation 7. Epithelium regeneration
Acne - Bacterial (rod) provocation - Excess secretion by sebaceous glands Warts - Viral invasion of skin Dermatitis and Eczema Inflammatory skin conditions Nonspecific allergenic responses Psychosomatic condition - Site of expression of stress-induced imbalances Low protein diet Black current oil (GLA - gamma linolenic acid) Poultice of Chaparral (Larrea divaricata) and Calendula lotion and aloe Psoriasis Small reddish-brown elevations Bleed when scraped from tops of papillae Skin cells mature too rapidly - in only three or four days instead of 28 - abnormal cells build into inflamed, elevated lesions - become covered with dead skin (scales) Treatment moisturizers mild soaps corticosteroid creams phototherapy UV light psoralen Healthy diet - immune response Contraindicated - ethanol National Psoriasis Foundation 6600 Southwest 92 nd Ave. Suite 300 Portland, Oregon 97223 800-248-0886 Sty - Infection of gland at the root of an eyelash Acute, painful inflammation Contagious, may be spread Chalazion - meibomian cyst Swelling of eye lid gland Oily secretion to Lubricate Protect Secretion thickens and clogs duct Infection causes red, sore eyelid Non-contagious Treatment Warm compresses Steaming Antibiotics Draining Impetigo - contagious Staphylococcus Streptococcus Moles Pigmented skin growths Can become malignant ABCs Abnormal growth Border ragged Color changes Herpes Simplex Viral infection of nerves Manifests as blisters at papillary layer Herpes Zoster (Shingles) Similar to chicken pox Blister around torso Cancer Epidermis Dermis Sudoriferous Sebacious Heat Stroke Loss of water Loss of electrolytes Regulation of body temperature