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13 Cards in this Set
- Front
- Back
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Epidermis |
-Composed of keratinized, stratified squamous epithelium -thick skin: five distinct layers, only found on palms/fingers, has sweat glands but no hair follicles or sebaceous glands -thin skin: four distinct layer, found everywhere else, has sweat glands hair follicles and sebaceous glands |
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Layers of the Epidermis |
Stratum corneum- dead keratinocytes as layers of keratin and glycolipids Stratum granulosum- keratinocytes adhered by desmosomes producing keratin and glycolipids Stratum spinosum- keratinocytes dying as they rise too far from diffused nutrients Stratum basale- mitosing basal cells, keratinocytes, melanocytes, and merkel cells |
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Cells of the Epidermis |
Keratinocytes- >undergo mitosis in stratum basale to create all layers >Synthesize keratin for toughness and glycolipids for water proofing >Pick up melanin granules Melanocytes- >only in stratum basale >synthesize pigment melanin that absorbs UVR to protect DNA in mitosing cells>branched processes deliver melanin to keratinocytes Merkel cells- >only in stratum basale >light touch receptor cells associated with Merkel disc (sensory nerve) in the dermisLangerhan Cells- >marcrophages originating in bone marrow that guard against pathogens >found in stratum spinosum >engulf and kill bacteria with lysosomal enzymes |
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Dermis |
Consists of two layers- Papillary: >areolar loose CT >dermal papilla push up epidermis creating friction ridges >blood capillaries diffuse O2 and nutrients into the epidermis >bare nerve endings sense pain and temperature >meissners corpuscle senses light touch>merkel discs sits under merkel cell to sense light touch Reticular: >dense irregular CT- collagen provides tensile strength to resist pulling, some elastin for elasticity >becomes leather in tanning process >site of Pacinian corpuscle which senses deep pressure >site of skin accessory structures- hair follicles, sebaceous glands, and sweat glands |
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Hypodermis |
>connects skin to underlying bone and muscle >subcutaneous fat- adipose- for shock absorption, thermal insulation, energy storage |
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Blood vessels in skin |
Dermis- blood vessels will dilate as body temp increases for radiant cooling and constrict when cold to minimize heat loss Hypodermis- blood vessel hold up to 5% of the total blood volume, during bleeding vessels constrict and push blood into the core as an autotransfusion to maintain blood pressure |
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Skin pigmentation |
>melanin is the primary pigment for skin >two types: eumelanin & pheomelanin>melanin is created by melanocytes which are picked up by keratinocytes in the stratum spinosum >melanosomes are situated under the apical surface of the keratinocytes and create a blanket effect across the skin >the melanin absorbs UVR which protects the DNA of mitosing cells in the stratum basale from damage and prevents the breakdown of folic acid needed for DNA synthesis >excessive UVR exposure damaging DNA predisposes to skin cancer >all skin has the same number of melanocytes but differs in the amount of melanin production |
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UVR exposure |
Skin cancer types: Basal cell carcinoma-arises from the stratum basale, does not metastasize Squamous cell carcinoma- arises from stratum spinosum, may metastasize to lymph nodes Malignant melanoma- arises from melanocytes, metastasizes early usually to brain, not responsive to most chemotherapies |
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Vit D synthesis |
>UVR is needed in skin for th synthesis of vitamin D >UVR activates a cholesterol precursor into vitamin D3 or cholecalciferol >cholecalciferol then goes sequentially to the liver and kidney for the final activation steps >Vit D is required for calcium absorption from food in the small intestines |
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Hair/Hair follicle |
>the hair follicle grows from the epidermis deep into the reticular layer of the dermis >the hair is created as a keratin filament by the keratinocytes of the hair matrix located in the hair bulb; melanocytes there deliver pigment for hair >blood capillaries located in the hair papilla deliver O2 and nutrients to the keratinocytes and melanocytes >the hair grows upward through the area of the root and when exposed to the surface of the skin is called the hair shaft >the arrector pili made of smooth muscle under sympathetic nervous system control pulls the hair erect as “goose bumps” |
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Sebaceous Glands |
>Sebaceous glands hang off of a hair follicle and provide oil to lubricate growing hair >they are holocrine sweat glands where cells produce oil until they burst, releasing oil and cell debris (sebum) >during puberty androgen hormone causes hair to become thicker and causes the sebaceous gland to increase sebum production as more is needed to lubricate thicker hair >in hairless follicles found on the face, chest, and back the sebum can become blocked without a hair to pull it out of the follicle, resulting in acne |
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Eccrine sweat gland |
>found all over the skin surface, small in size, ducts empty onto skin surface >merocrine gland type where sweat is secreted by exocytosis Functions: >evaporative cooling >acid mantle- vit C and lactic acid in sweat lowers the skin ph to about 3-5 which inhibits bacteria growth >toxin excretion- heavy metals like mercury and lead can be excreted in sweat to detoxify the body |
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Apocrine Sweat gland |
>found only in axillary and genital regions, ducts empty into nearby hair follicle, huge >apocrine type sweat gland where sweat is secreted by being pinched off in a bit of cell membrane into the duct >the proteins and lipids of the cell membrane are used as a diet by bacteria and their waste is what causes odor >secretes pheromones |
