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Published byJason Stevens Modified over 9 years ago
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Includes your entire outer layer of skin (16% of your total body weight), accessory organs like hair, nails, and glands. Consists of two major parts: (1) Cutaneous membrane (2) Accessory structures
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Made up of two layers: (1) Epidermis (superficial epithelium), and Dermis (underlying connective tissue) (2) Accessory structures – Including hair, nail, exocrine glands. Located mostly in the dermis and protrude into the epidermal layer (3) Subcutaneous layer deep to the dermis is known as the hypodermis; often not considered part of the integumentary system, but because its fibers extend into the dermis, we will include it here
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(1) Protection of underlying tissues and organs against shocks, abrasion, and chemicals (2) Excretion of salts, water, and organic wastes (3) Maintenance of normal body temperature via insulation or evaporative cooling (sweating) (4) Synthesis of vitamin D3 (5) Storage of nutrients – including lipids/adipose (6) Detection of touch, pressure pain, and temperature stimuli and relaying information to the control center (brain)
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Recall epidermis composed of stratified squamous cells for the purpose of protection Most abundant epithelial cells are called keratinocytes
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Keratinocytes make up five layers of thick skin, and four layers in thin skin Thick skin is found in the palms of your hands and soles of your feet Thin skin is found everywhere else in your body Thick and thin refer to the thickness of the epidermal layer
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Top layer of skin Bottom layer of skin
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Stratum germinativum, also known as stratum basale, is the bottom most layer of skin Epidermal ridges are found here, and they extend into the dermis. Projections called dermal papillae creates an interlocking arrangement that increases the strength of the bond between the dermal and epidermal layers
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The contours of the skin surface follow the ridge patterns Ridges on the palms and soles of feet increase the skin’s surface area and friction, helping to maintain grip Ridge shapes are genetically determined, unique to you, and do not change throughout your life Ridge prints located on your fingers are called fingerprints
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Basal cells dominate this layer. Basal cells are stem cells whose divisions replace skin cells lost to shedding at the skin’s surface Merkel cells are also found in this layer. Merkel cells are sensitive to touch. Basal Cell
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Melanocytes are pigment cells that give skin its color; they are also found in this layer
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Means “spiny layer” Contains Langerhans cells, which are part of the immune system Langerhans cells are responsible for stimulating a defense against: (1) microorganisms that penetrate the epidermis (2) superficial cancer cells
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Known as the “grainy layer” By the time the cells reach this layer, they have stopped dividing and now begin to make lots of the protein keratin Keratin makes up our hair and nails
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Present only in thick skin “Clear layer” filled with keratin
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Top layer of epidermis; consists of 15-30 layers of cells Keratinization or cornification, is the formation of protective, superficial layers of cells made of keratin Dead layers of cells so tightly connected that when they slough off they separate as sheets of cells
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Takes 15-30 days for epithelial cells to move from stratum basale/germinativum to the stratum corneum They stay in the stratum corneum for about two weeks before being washed/shed
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A dry layer, so few microorganisms can survive here Layer is water resistant, but not waterproof. Water from inside the body slowly penetrates to the surface where it is evaporated. We lose ~500mL (1 pint) of water/day This process is called insensible perspiration If this layer is damaged or lost (as in burns), the rate of water loss dramatically increases and you are at risk of dehydration
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Recall from biology that freshwater will move into cells, causing them to SWELL This is why when you take a bath your hands swell and look like raisins Likewise, water will leave cells if placed in highly concentrated solutions, like oceanwater Although the process occurs slowly, it will accelerate the dehydration process in shipwreck survivors After 51 hours of exposure to seawater and wearing gloves
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