the integumentary system

• components:

  1. skin
  2. hair
  3. nails
  4. exocrine glands
  5. sweat glands (sweat)
  6. sebaceous glands (oils)
  7. sensory receptors and arrector pili muscles
• cutaneous membrane

  1. epidermis: epidermis tissue
  2. hair
  3. sebaceous gland
  4. dermis: loose connective & dense irregular connective tissue
  5. arrector pili muscle
  6. hypodermis: loose connective & adipose tissue
  7. sweat glands
  8. sensory receptors
• integument functions:

  1. protection
  2. mechanical trauma, pathogens, outside environment
  3. sensation
  4. numerous sensory receptor
  5. thermoregulation
  6. sweat glands & vasomotion
  7. excretion
  8. lactic acid & urea
  9. vitamin D synthesis
  10. exposure of cholesterol precursors to UV radiation (cholecalciferol --> liver --> kidneys --> calcitiol
• vasoconstriction: when you get hot thermoreceptors tell the hypothalamus of the brain to secrete sweat
• Order of epidermis layers (bottom to top):

  1. stratum basale
  2. stratum spinosum
  3. stratum granulosum
  4. stratum lucidum
  5. stratum corneum

  Brilliant Studying Gives Loads of Confidence
• stratum corneum: layer of dead keratinocytes (flattened layers of keratin). The most superficial layers lose desmosomes, slough off
• stratum lucidum: clear layer of dead keratinocytes (thick skin only)
• stratum granulosum: numerous cytoplasmic granules containing. keratin bundles OR lipid based substance. lipid based substances secreted, waterproofs, cuts cells off from basal lamina
• stratum spinosum: some cells still mitotically active starting produce keratin components
• stratum basale: single layer of stem cells (mitotically active rests on basement membrane (basal lamina + reticular lamina)
• epidermis cells:

  1. 95% keratinocytes
  2. 5%
  3. dendritic cells
  4. merkel cells
  5. melanocytes
• epidermis cells have a 40-50 day cycle
• dendritic cells: in stratum spinosum (langerhans cells) phagocytes

  melanocytes: in stratum basale produces melanin pigment

  merkel cell: in stratum basale sensory cells associated with neurons detect light touch and textures
• epidermis = papilary layer

  • dermal papillae
  • tactile corpuscle

  dermis = reticular layer

  • lamellated corpuscle
• papillary layer: loose connective tissue dermal papilae extend up into epidermis contain capillary networks & tactile (Meisner) corpuscles
• reticular layer: dense irregular connective tissue strength (collagen) and elasticity (elastic fibers)

  hydration: proteoglycans, hydrates skin

  contains: blood vessels, sweat glands, sebaceous glands & lamellated (Pacinian) corpuscle
• Skin types:

  1. fingerprints: prominent dermal papillae arranged into dermal ridges by thick collagen fibers
  2. causes prominent epidermal ridges that enhance gripping ability on hands & feet
  3. tension lines: gaps between collagen bundles in reticular layer indent epidermis to form tension lines
  4. wound healing & scarring
  5. flexure lines: reticular layer bound tightly to deeper tissues
  6. prominent around joints and palms
• skin pigmentation

  1. melanin: orange-red to black pigment
  2. protects DNA from UV radiation
  3. Di-peptide (2x tyrosine)
  4. produced by melanocytes in the stratum basale
  5. carotene: yellow-orange pigment
  6. some used as vitamin A precursors
  7. unsaturated lipids
  8. obtained from diet (egg yolk, carrots), stored in adipose tissue
  9. hemoglobin: red pigment (iron oxidation)
  10. binds oxygen in erthrocytes
  11. quaternary structure protein with 4 polypeptides
  12. protein synthesis in erthrocytes
• melanin

  • synthesized in melanosomes
  • tyrosinase catalyzes peptide bond formation between 2 tyrosine
  • melanin released by exocytosis, taken up by keratinocytes using endocytosis
  • melanin in keratinocytes accumulates superficial to the nucleus, shielding DNA from UV radiation
  • melanocytes are found in stratum basale of epidermis
• different examples of pigmentation:

  • freckles (localized higher melanin production)
  • & moles (localized proliferation of melanocytes
  • erythema: reddening of skin (dilation of capillaries), hemoglobin bright red when bound to oxygen
  • albanism: melanocytes do not produce tyrosinase
  • pallor: decreased blood flow, pale or white appearance (collagen in dermis)
  • healthy tans
  • red lips: thin stratum corneum so appear more red
  • cyanosis: bluish skin, extremely low oxygen bound to hemoglobin (darker red purple)
• UV radiation has both immediate and delayed effects on skin pigmentation

  all people can develop sunburns

  immediate response: oxidation of melanin already present in keratinocytes; causes melanin to quickly darken

  red from inflammation and increased blood flow in the capillaries

  delayed or secondary production: appears within 72 hours; last longer than melanin oxidation

  secondary function of melanin: reduces synthesis of vitamin D in response to UV radiation; leads to less calcium ion absorption and maintenance of calcium ion homeostasis within narrow range
• individuals living in regions exposed to high amounts of UV radiation developed darker skin to prevent excess vitamin D production and individuals in areas with less UV radiation developed lighter skin so they could synthesize enough vitamin D
• skin color depends on number of melanocytes in particular body region:

  • differences lead to uneven distribution of melanin; fewer melonocytes on palms of hand and soles of feet
  • overall number of melanocytes is virtually identical among all individuals, irrespective of skin color
  • spectrum of human skin tones is due to differences in amount of tyrosinase activity and type (color) or melanin produced
• accessory structures:

  1. hair: derived from skin epithelium
  2. protective & sensory functions: eyebrows, nose-hairs, head hair (UV)
  3. lanugo: thin non-pigmented hair on fetus
  4. terminal hair: scalp & around eyes
  5. vellus hair (body hair, somewhat replaced by terminal hair after puberty
  6. nails: derived from skin epithelium
  7. protective and griping functions
  8. glands: derived from skin epithelium
  9. various functions
  10. sweat glands
  11. eccrine
  12. apocrine
  13. ceruminous
  14. mammary
  15. all merocrine secretion
  16. sebaceous glands
  17. produces and secrete sebum holocrine secretion
• glands

  sweat glands:

  1. eccrine: most prevalent, water, electrolytes, lactic acid
  2. apocrine: release into hair follicle, rich in protein that bacteria metabolize a produce odor, axillae (armpits), anal area, areolae
  3. ceruminous: modified apocrine in ear, produce cerumen (Ear wax)
  4. mammary: mammary glands which produce milk
  5. all merocrine secretion (exocytosis)

  sebaceous glands:

  produce and secrete sebum (oily lipids), empties into hair follicle, numerous on face and scalp factor in acne

  1. holocrine secretion (Cells rupture and release)
• wound: any disruption in skin's integrity; includes

  1. lacerations (cuts)
  2. burns
  3. skin cancers
• skin cancer

  • cancer: one of the most common diseases in the world; caused by mutations in DNA; induces cell to lose control of cell cycle
  • unchecked cell division eventually leads to formation of large population of undifferentiated cells (tumor)
  • cancerous tumors are able to metastasize
  • damage caused by metastic tumor cells alters function of invaded organs
  • other factors that increase risk for developing cancer include exposure to
  • carcinogens: cancer-inducing chemicals, toxins, or agents
  • forms of radiation
• metastasize: tumor cells spread through blood or lymphatic vessels to other tissues and continue to divide
• 3 cancers affect skin; linked to UV radiation exposure

  1. basal cell carcinoma
  2. squamous cell carcinoma
  3. malignant melanoma
• basal cell carcinoma

  • most common of all cancer types
  • arises from keratinocytes in stratum basale of epidermis
  • appears as nodule with a central crater
  • rarely metastisizes to other tissues
  • can be resolved successfully with surgical removal
• squamous cell carcinoma

  • second most common skin cancer
  • cancer of keratinocytes of stratum spinosum
  • scaly plaques may ulcerate and bleed; usually on head and neck
  • tumors are more likely to metastasize than basal cell carcinoma; surgical removal is still useful
  • second most likely to metastasize
• malignant melanoma: cancer of melanocytes

  • early detection of melanoma is critical due to tendency to metastasize
  • "arms" of cancerous melanocytes extend down into dermis and access dermal blood vessels; enables cells to spread to other tissues via bloodstream
  • treated with surgical removal; possibly radiation therapy and chemotherapy
  • prognosis depends on size of tumor, depth to which it extends into dermis, and whether it has metastisized to other tissues
• hyperpigmentation: overproduction in melanin, tan or brown patches

  • seen during pregnancy and Addison's disease and drug induced
  • Melasma: dark patches mainly on face, can occur usually only during pregnancy
• hypopigmentation: decreased melanin production or destruction of melanocytes

  • vitiligo: autoimmune disorder in which melanocytes are damaged
  • tinea versicolor (pityriasis veriscolor)
  • fungal infection
  • can be hypo or hyper
• stratum basale is where the melanocytes are located
• what cells of the epidermic function as phagocytes of the immune system?

  dendritic cells
• which of the following cells is associated with the dermis?

  fibroblast
• what tissue composes the reticular layer of the dermis?

  dense irregular connective tissue
• the primary function of vitamin D is required for calcium absorption from the small intestine
• what are the sensory receptors in the dermal papillae that responds to light, touch, and stimuli called?

  tactile (Meissner) corpuscles