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Human skin
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<p>The human skin is the outer covering of the body and is the largest organ of the <a href="/facts/Integumentary_system/vCEm01JG">integumentary system</a>. The skin has up to seven layers of <a href="/facts/Ectodermal/lg5p0jTL">ectodermal</a> <a href="/facts/Tissue_(biology)/H7CpML7A">tissue</a> guarding <a href="/facts/Skeletal_muscle/en1tVYFN">muscles</a>, <a href="/facts/Bone/pCU37jBe">bones</a>, <a href="/facts/Ligament/xAf6lB1z">ligaments</a> and <a href="/facts/Organ_(anatomy)/FUYsLaxz">internal organs</a>. Human skin is similar to most of the other <a href="/facts/Mammal/phSwTzBo">mammals</a>' skin, and it is very similar to <a href="/facts/Pig/b5wxwdDY">pig</a> skin. Though nearly all human skin is covered with <a href="/facts/Hair_follicle/SXsAKufM">hair follicles</a>, it can appear <a href="/facts/Nudity/vbVcL8SP">hairless</a>. There are two general types of skin: hairy and <a href="/facts/Glabrous_skin/L7vt9FL3">glabrous skin</a> (hairless). The adjective <a href="/facts/List_of_medical_roots%2c_suffixes_and_prefixes/0jVDvfru"><i>cutaneous</i></a> literally means "of the skin" (from Latin <i>cutis</i>, skin). </p><p>Skin plays an important <a href="/facts/Immunity_(medical)/vLPpzSNL">immunity</a> role in protecting the body against <a href="/facts/Pathogen/axMXtV1M">pathogens</a> and excessive <a href="/facts/Transepidermal_water_loss/QaqAk6l9">water loss</a>. Its other functions are <a href="/facts/Thermal_insulation/j7tVT4uv">insulation</a>, <a href="/facts/Thermoregulation/V692hIjw">temperature regulation</a>, sensation, synthesis of <a href="/facts/Vitamin_D/No0zQB2W">vitamin D</a>, and the protection of <a href="/facts/Vitamin_B/m6ekXy6A">vitamin B</a> folates. Severely damaged skin will try to heal by forming <a href="/facts/Scar/XSQ92JoG">scar tissue</a>. This is often discoloured and depigmented. </p><p>In humans, <a href="/facts/Human_skin_colour/nkMestc6">skin pigmentation</a> (affected by melanin) varies among populations, and skin type can range from <a href="/facts/Dry_skin/kJLKYrNA">dry</a> to non-dry and from <a href="/facts/Sebaceous_gland/HKMXmv1Y">oily</a> to non-oily. Such skin variety provides a rich and diverse habitat for the approximately one thousand species of <a href="/facts/Bacteria/wC8xSCsU">bacteria</a> from nineteen <a href="/facts/Phylum/ELT3Jyax">phyla</a> which have been found on human skin. </p>