Histo Lecture 5

  1. Two Functions of the Barrier System
    • -Protection from Microorganisms and UV light
    • -Relatively permeable to water (prevents evaporation of body fluids)
  2. Definition of Sensation
    Highly innervated with lots of receptors
  3. Definition of Thermoregulation
    Sweat glands, vasodilation
  4. Definition of plasticity/elasticity
    Allows for changes in size and shape
  5. 3 Layers of skin
    • -Epidermis
    • -Dermis
    • -Hypodermis (subcutaneous tissue)
  6. Characteristics of Thick Skin
    • -400-600 μm (thickness)
    • -Hairless
    • -Location: Soles of feet and palms
  7. Characteritics of Thin Skin
    • -75-100 μm
    • -Hairy
    • -Location: Everywhere else
  8. 5 Layers of Epidermis
    • -Stratum Basale
    • -Stratum Spinosum
    • -Stratum Granulosum
    • -Stratum Lucidum
    • -Stratum Corneum
  9. Function of Stratum Basale
    • -Single layer of cuboidal cells sitting on basement membrane that undergo intense mitotic division
    • -Renewed about every 15-30 days
  10. Describe Stratum Spinosum
    • -"spiny cells"; cuboidal cells like stratum basale
    • -Filled with keratin filaments that are anchored into desmosomes
    • -Desomosomes firmly bind cells of this layer together
    • -Function: resist abrasion
  11. Describe Stratum Granulosum
    • -3-5 layers of squamos cells; cytoplasm filled with vesicles
    • -Vesicles fuse with the cell membrane and discharge contents into the intercellular space
    • -Secreted material contains high concentration of lipid molecules
    • -Function: Provides an intercellular cement. Creates a barrier to foreign materials
  12. Define Stratum Lucidum
    • -Most apparent in thick skin; minimal layer in thin skin
    • -Translucent layer of squamos cells with no apparent organelles
    • -Densely packed keratin filaments anchored to desmosomes (provide strength to this layer)
    • -Function: Resist abrasion
  13. Describe Stratum Corneum
    • -Outermost surface of skin
    • -15-20 layers of flattened non-nucleated cells; cytoplasm filled with keratin (i.e. "keratinized")
    • -Cells consist of only keratin fibers, proteins and thick cell membranes (no organelles; lifeless cells)
    • -Cells of this layer are continuously shed; termed "desquamation"
  14. Properties of Keratinocytes
    • -Generic term
    • -Epithelial cell in any & all layers
  15. Properties of Melanocytes
    • -Produce melanin
    • -Found in basal layer
  16. Langerhans' cells
    • -Skin macrophages
    • -Inner layer of epidermis
  17. Properties of Melanocytes
    • -Location: Between stratum basale and spinosum
    • -Synthesize melanin (dark pigment protects from UV radiation)
    • -Melanin is transferred to keratinocytes at deep layers of skin and deposited "on top" of cell nuclei
    • -Highest concentration of melanin occurs in cells in deeper layers of skin
  18. Facts about Langerhan's cells
    • -Resident "macrophage-like" cells of skin
    • -Found in stratum basale and stratum spinosum
    • -Represent approx. 2-8% of epiermal cells
    • -Bone marrow derived; carried to the epidermis via the blood
    • -Can bind and present antigen to lymphocytes for immune functions against micro-organisms
  19. Components of Dermis
    • -Loose CT (papillary layer) and dense irregular CT (reticular layer)
    • -Neuronal innervation (skin sensory receptors)
    • -Blood vessels are abundant in the dermis
  20. Skin appendages of Dermis
    • -Hair follicles, nails
    • -Sebaceous glands, sweat glands
  21. Facts about Subcutaneous Layer
    • -Loose CT that binds skin to underlying structures (hypodermis, superficial fascia)
    • -Often contains numerous fat cells
    • -Also contains neurovascular networks
  22. 3 Types of Epithelial glands
    • -Holocrine
    • -Merocrine
    • -Apocrine
  23. Holocrine gland
    -Secretory product is released along with the entire contens of the cell
  24. Merocrine (eccrine) gland
    -Secretory product is released through exocytosis
  25. Apocrine gland
    -Secretory product is released with portion of cellular cytoplasm
  26. Facts about sebaceous glands
    • -Consist of epithelial cells that take up large quantities of lipids
    • -Cells die and release lipid (sebum) into the hair follicle
    • -Sebum has antibacterial and antifungal properties
    • -These glands are found over most of the body; highly concentrated in face and scalp
    • -A type of holocrine gland
    • -Lipids are excreted with remnants of a dead cell
  27. Facts about Merocrine sweat glands
    • -Coiled tubular glands opening onto skin surface
    • -Ducts release sweat onto skin surface when body temperature increases
    • -Sweat evaporates cooling the skin surface
    • -Sweat composition: water, NaCl, urea, uric acid, ammonia
  28. Properties of Apocrine sweat glands
    • -Release a viscous, odorless fluid
    • -Bacterial decomposition of fluid creates a distinctive scent
    • -Found in axillary and ano-genital regions
    • -Fluid is released onto hair follicles
    • -Controlled by ANS
  29. Properties of Skin Receptors
    • -Responsible for touch-pressure, tactile perception, hot-cold, pain and itching
    • -Most are found within dermal layer
  30. Types of Sensory Receptors
    • -Free nerve endings - pain/temperature
    • -Ruffini's endings - pressure/vibration
    • -Pacinian corpuscles - touch receptors
    • -Meissner's corpuscles - touch receptors
  31. Properties of Nails
    • -Plates of keratinized epithelial cells
    • -Nail root is source of dividing cells for growth
    • -Cuticle is formed from the stratum corneum
    • -Nail bed contains basale and spinosum only
  32. Facts about nail growth
    • -Matrix - proximal portion of nail bed contains dividing cells
    • -Cells divide, more distally and are cornified at proximal part of nail plate
    • -Nail plate "slides" forward over nail bed as new nail material is added
  33. Facts about hair follicle
    • -Derived from invaginations of epidermal cells
    • -Dermal papilla contains dividing cells for hair growth and blood supply
    • -Erector pili muscle contraction causes "goose bumps"
    • -Melanocytes provide pigment for hair color
  34. Facts about Hair Growth
    • -Hair grows approx. 6 inches/yr, random growth cycles
    • -3 phases: Catagen, Telogen, Anagen
  35. Catagen
    • -3% of all hairs
    • -2-3 week phase
    • -No growth occuring
  36. Telogen
    • -10-15% of all hairs
    • -Lasts 100+ days
    • -Full resting phase; no growth occurs, hair loss
  37. Anagen
    • -Active growth phase
    • -30-45 days up to 2-6 years
  38. Effects of Aging on skin
    • -Atrophy of strata of skin (layers become thinner and more fragile)
    • -Reduced elasticity
    • -Areas of skin exposed to sun are affected more rapidly
    • -Reduced sweat capability
  39. Effect of Acute Activity on skin causes:
    • -blood flow to skin to decrease with activity levels >50%
    • -Vasoconstriction and dilation control sin blood flor and may be altered by hot environments
  40. Effects of chronic Training on Skin
    • -Hyperplasia of skin (callous formation)
    • -Increased ability to sweat (Improved thermoregulatory ability
    • -Blisters
  41. Describe a blister
    • -Fluid deposition at junction of epidermis and dermis
    • -Epidermis to be raised away from the dermis
    • -Most commonly caused by excessive shearing forces
  42. Effects of Immobilization on skin
    • -Increased risk of skin breakdown = pressure ulcer
    • -High pressure areas include: Heels, sacrum, greater trochanter, scapula, elbows, back of the head
  43. Epidermal Specialization on Back, abdomen, thighs, arms
    • -thin epidermis, loosely packed keratin
    • -Few follicles produce fine hairs, variable eccrine glands
  44. Sole of foot specializations
    • -Thick epidermis, densely packed ekratin
    • -Developed epidermal ridge system
    • -No hair follicles, abundant eccrine glands
  45. Scalp epidermal specializations
    -tightly packed follicles
  46. Fingertip epidermal specializations
    -Thick epidermis, developed ridges, abundant sensory receptors
  47. Axilla/groin epidermal specializations
    • -Thin epidermis, numerous oblique hair follicles
    • -Numerous eccrine and apocrine glands
Card Set
Histo Lecture 5
The Integument