Hair follicle receptor – contains nerve endings • Surrounds each hair bulb • Allows us to feel when something touches our hair
Nails • Nail = keratinized cells of the epidermis that form a clear protective covering on ends of fingers and toes – Nails contain hard keratin • Each nail has a free edge, a body, and a root – Root is embedded in the skin • Nail bed - the deeper layers of the epidermis extend beneath the nail
Nails • Nail matrix – part of nail bed responsible for nail growth • Nails appear pink because of capillaries in the underlying dermis • Region of nail bed that lies over the thick nail matrix appears as a white crescent called the lunula
Functions of Skin • Protection – acts as a chemical, physical and biological barrier • Body temperature regulation • Cutaneous Sensation – Skin is supplied with cutaneous sensory receptors • Meissner’s corpuscles - allow us to sense something against our skin • Pacinian corpuscles – allows us to feel pressure • Hair follicle receptors • Nerve endings – alert us of pain
Functions of Skin • Metabolic functions – production of vitamin D from sunlight • Blood Reservoir – dermis is highly vascularized • Excretion – elimination of nitrogenous wastes (urea, ammonia, uric acid) as sweat
Skin Cancer • 1 in 5 Americans will develop skin cancer at some point in their lives • Most skin tumors are benign and do not metastasize (spread to other areas) • Crucial risk factor for skin cancer is overexposure to UV radiation in sunlight – Damages DNA bases – causes cross-linking of DNA strand called “primer dimers” – UV radiation also disables a tumor suppressor gene called p53
Skin Cancer • Cells with severely damaged DNA die after prolonged exposure to the sun – Causes skin to peel after a sunburn • Cells that DON’T die could have mutated DNA – When cells proliferate – DNA damage could lead to uncontrolled growth cancer • New skin lotions claim that they can fix damaged DNA in cells before they develop into cancer cells – Lotions contain enzymes to repair cross-linked DNA strands
Basal Cell Carcinoma • Basal cell carcinoma - most common type but least malignant and of skin cancer • Cancer lesions occur most often on sun-exposed areas of the face • Appear as shiny, dome-shaped nodules that later develop a central ulcer • Slow-growing, rarely metastasizes • Growth is removed by surgical resection
Squamous Cell Carcinoma • Squamous cell carcinoma - arises from the keratinocytes of the stratum spinosum • Lesion appears as a scaly reddened papule (small, rounded elevation) • Usually found on the head (scalp, ears, and lower lip), and hands • Grows rapidly and metastasizes if not removed
Melanoma • Melanoma - cancer of melanocytes • Rare, but most dangerous type of skin cancer • Can be treated if caught early • Highly metastatic and resistant to chemotherapy • Accounts for about 5% of skin cancers –
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- Spring '18
- dr. erin
- Stratum lucidum, Stratum Corneum, Stratum Granulosum, Eccrine sweat glands