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Chapter 6FibroblastThese are large, fusiform cells that often show slender, wispy branches. They producethe fibers and ground substance that form the matrix of the tissue (fibrous).Melanocytes synthesize melanin. Distribute melanin from cell processes. The melanin is picked up by keratinocytes and used to shade their nuclei from UV radiationMerkel Cells touch receptors associated with nerve fibers to form Merkel disc Dendritic cells(immune) also called Langerhans are macrophages from bone marrow that migrate to the epidermis. They help protect the body against pathogens by presentingthem to theimmune system. Squamous cell carcinoma comes from these cellsKeratinocytescells that undergo mitosis to replace epidermis, they form most of the cells of the epidermisEPIDERMAL LAYERS:STRATUM BASALE: keratinocytes, melanocytes, merkel cells, stem cellsSTRATUM SPINOSUM: keratinocytes attached to each other by desmosomes which makes them look spiny, dendritic cellsSTRATUM GRANULOSUM: keratinocytes. Contains keratohyalin granules (which become keratine by action of the intermediate filaments). Barrier between epidermis and deeper layers. Cuts off surface strata from nutrient supply. STRATUM LUCIDUM: Seen only in thick skin. Keratinocytes with eleidin (keratin precursor), cells have no nucleus or organellesSTRATUM CORNEUM: dead keratinized cells (surface cells flake off) Thick skin soles, palm, (stratum corneum)Dermis--- fibrous connective tissue with blood vessels, nerve endings, sweat glands and hair folliclesDERMAL LAYERSPapillary layer superficial 1/5 epidermis areolar tissueReticular layer, deeper 4/5, dense irregular connective tissueHypodermis or subcutaneous tissue more areolar than adipose tissueSKIN COLOR melanin is responsibleAlbinism, genetic lack of melanin that results in milky white hair and skin, blue-gray eyesCyanosis, blueness of the skin from lack of oxygen
Jaundice, yellowing of skin and whites of the eyes due to high bilirubin levelsHematoma or bruise is a mass of clotted blood showing through the skinVITAMIN D Synthesisis a function of the skin: epidermal keratinocytes use ultraviolet