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• Function THE SKIN – Protective covering • Bacterial infection • Physical trauma – Receptors • Touch, pressure, pain, heat and cold – Vitamin D production • UV light – Regulation of body temperature • Dilation or constriction of blood vessels • Sweat glands SKIN REGIONS Epidermis Dermis Hypodermis (Subcutaneous Layer) SKIN REGIONS • Epidermis – Protective outer epithelial layer – Avascular SKIN REGIONS Dermis Tough, fibrous connective tissue layer Largest region of the skin Vascular SKIN REGIONS Hypodermis Region just deep to the dermis Adipose and areolar C.T. Anchors the skin LAYERS of the EPIDERMIS Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale THE EPIDERMIS • Definition – Keratinized, stratified squamous E.T. • Layers – Five layers in thick skin – Four in all other skin THE EPIDERMIS • Cells – Keratinocytes • Most numerous cell type • Produce the protein keratin for waterproofing and protection • Replaced every 25 to 45 days EPIDERMAL LAYERS • Stratum Basale – Deepest layer – Attached to dermis – Single layer of cuboidal keratinocytes – Mitotic layer – Contains melanocytes • Produce the pigment melanin – Contains Merkel’s discs = • Sensory nerve endings • Pressure EPIDERMAL LAYERS: Stratum Basale melanocytes EPIDERMAL LAYERS Stratum Spinosum Several layers of keratinocytes with a “spiny” appearance Scattered melanin granules Langerhan cells = macrophages EPIDERMAL LAYERS: Stratum Spinosum EPIDERMAL LAYERS Stratum Granulosum Thin region of darkstaining cells Flat cells with keratohyaline granules Cells above are dead EPIDERMAL LAYERS: Stratum Granulosum EPIDERMAL LAYERS Stratum Lucidum Only present in thick skin Thin, translucent layer of dead keratinocytes EPIDERMAL LAYERS: Stratum Lucidum EPIDERMAL LAYERS Stratum Corneum Outer, loose layer of dead, flaky cells Protects skin from: Abrasion or penetration EPIDERMAL LAYERS: Stratum Corneum THE DERMIS Definition A thick, flexible C.T. layer Rich in nerve fibers Very vascular Layers Papillary layer Reticular layer THE DERMIS LAYERS of the DERMIS dermal papillae Meissner’s corpuscle Papillary Layer Loosely woven Highly vascular Contains: Dermal papillae Meissner’s corpuscles • Detect touch Free nerve endings • Detect pain Larger dermal folds form ridges = fingerprints On palms of hands and soles of feet STRUCTURES of the DERMIS dermal papilla epidermal peg STRUCTURES of the DERMIS Meissner’s Corpuscle LAYERS of the DERMIS Reticular Layer Makes up 80% of the dermis Dense, irregular C.T. rich in collagen Contains: Hair follicles Sebaceous glands Blood vessels and nerves Pacinian corpuscles in deep regions • Detect crude touch; deep pressure Pacinian corpuscle STRUCTURES of the DERMIS Pacinian Corpuscle SKIN COLOR Three Pigments Determine Skin Color Melanin Brown to black pigment Prevents UV damage Carotene Yellowish, orange pigment Noticeable in the palms and soles Hemoglobin Red pigment when oxygenated Gives the skin a bluish or gray appearance when poorly oxygenated (cyanosis) APPENDAGES of the SKIN: Hair and Hair Follicles Definition Keratinized cells produced by hair follicles Hair Structure Papilla At the hair base Supplies the cells with nutrients Arrector pili Smooth muscles Pull hair upright Hair and Hair Follicles epidermal tissue papilla Hair and Hair Follicles Arrector Pili Muscle APPENDAGES of the SKIN: Hair and Hair Follicles Types of Hair Vellus Hair Soft body hair of children and adult females Terminal Hair Coarse, longer growing hair Found: • Eyebrows, head, armpits, pubic regions of adults • Face, chest, arms and legs of adult males APPENDAGES of the SKIN: Nails Definition Epidermal modifications Protects the dorsum of the fingers and toes Contain keratin APPENDAGES of the SKIN: Sudoriferous (Sweat) Glands Two Types: Eccrine Sweat Glands Open to skin surface Regulation of body temperature Merocrine sweat gland APPENDAGES of the SKIN: Sudoriferous (Sweat) Glands Apocrine Sweat Glands Open into hair follicles in anal, groin and axillary region Active at puberty Not important in thermoregulation Active during stress Apocrine sweat gland Sudoriferous (Sweat) Glands APPENDAGES of the SKIN: Mammary Glands Definition Modified sweat glands Within breasts Produce milk following childbirth mammary glands APPENDAGES of the SKIN: Sebaceous (Oil) Glands Definition Simple alveolar glands found all over the body except on the palms and soles Near hair follicles Secretes sebum Sebaceous gland Sebaceous (Oil) Glands SKIN DISORDERS Hyperthermia An abnormally high body temperature Can result in: • Heat exhaustion (headache, vomiting, and tiredness) • Heat stroke (dizziness, confusion, delusions) • Increased fluid intake and possible medical care are needed in both cases Fever • Hyperthermia brought on by illness • Body’s attempt to fight off infection SKIN DISORDERS Hypothermia An abnormally low body temperature Results in: • Shivering, incoherent speech and lack of coordination • Body functions slow and death occurs when metabolism stops completely • Person must be warmed immediately SKIN DISORDERS Skin Cancer Squamous cell carcinoma and basal cell carcinoma Most common Likely caused by sun exposure Surgical removal is the standard treatment Melanoma Arises from melanocytes Can metastasize SKIN CANCER Squamous Cell Carcinoma Basal Cell Carcinoma Malignant Melanoma SKIN DISORDERS Burns Factors affecting burn severity Depth of burn Extent of area burned Classification of burns 1st degree burns • Epidermis is burned: redness and pain • Damaged skin peels off SKIN DISORDERS Burns Classification of burns 2nd degree burns • Extends through epidermis and part of the dermis • Results in redness, pain and blisters • May result in scarring SKIN DISORDERS Burns Classification of burns 3rd degree burns • Entire thickness of skin is burnt • Blood vessels, sweat glands, and other skin accessories are also burnt • Fluid and heat loss and bacterial infection • Skin grafting required • Survival chances are not good if large area BURNS 1st Degree Burn 2nd Degree Burn 3rd Degree Burn
