lecture exam #2

• Skin cell types


  • Keratinocytes
  • Melanocytes
  • Langerhans cells
  • Merkel cells
• Keratinocytes


  Most abundant, originate in basal layer, produce keratin, responsible for epidermal water barrier, require calcium absorption by activation of cholesterol precursors by UVB light to form vitamin D
• Melanocytes


  Derive from neural crest cells, produce melanin, UVB light stimulates melanin secretion which protects against UV radiation, melanin produced when enzyme tyrosinase converts tyrosine to DOPA
• Langerhans cells


  Dendritic cells, skin's first line of defense, primarily found in stratum spinosum, part of mononuclear phagocytic system
• Merkel cells


  Oval-shaped modified epidermal cells found in stratum basale, directly above basement membrane, most populous in fingertips, serve as sensory function for touch, also in soles and palms
• Skin tissue type


  • Epithelial tissue, made up of 3 layers: epidermis, dermis, hypodermis
• Layers of epidermis


  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum lucidum
  • Stratum corneum
• Stratum basale


  Provides germinal cells/stem cells necessary for regeneration of epidermis, holds melanocytes
• Stratum spinosum


  "Prickly layer" between stratum basale and stratum granulosum, holds Langerhans cells
• Stratum granulosum


  Accumulate dense basophilic keratohyalin granules that hold stratum corneum together
• Stratum lucidum


  Represents transition from stratum granulosum to stratum corneum
• Stratum corneum


  Serves as epidermal permeability barrier and prevents excessive transepidermal water loss
• Layers of dermis


  • Papillary dermis
  • Reticular dermis
• Papillary dermis


  Superficial layer, lying deep to epidermis, composed of loose connective tissue that is highly vascularized
• Reticular dermis


  Thick layer of dense connective tissue that is the bulk of the dermis
• Hypodermis


  Mostly made up of connective tissue and adipose tissue, responsible for protecting skeletal system, organs, muscles and tissues
• Accessory structures


  • Sebaceous glands
  • Eccrine sweat glands
  • Apocrine sweat glands
  • Ceruminous modified sweat glands
  • Mammary modified sebaceous glands
  • Nails
  • Hair
• Sebaceous glands


  Microscopic glands found in hair follicles that secrete sebum, an oily substance that protects hair from drying out
• Eccrine sweat glands


  Occur over most of the body, secrete sweat directly onto the skin's surface
• Apocrine sweat glands


  Develop in areas with many hair follicles, such as scalp, armpits, and groin
• Ceruminous modified sweat gland

  With sebaceous glands, produce earwax to protect ear canal
• Mammary modified sebaceous glands

  Modified to produce milk
• Nails


  Made of dead keratinized cells, protect extremities of fingers and toes from damage
• Hair


  Made of dead keratinized cells, protects the skull from the sun
• Hair follicle


  Tube-like pore that surrounds the root and strand of hair, allows the hair to grow
• Sensory receptors


  • Touch
  • Pain/temperature
  • Pressure
• Touch sensory receptors


  In epidermis, dermis, and hypodermis, allow discrimination of touch/pressure differences (light touch), Meissner's corpuscles, Pacinian corpuscles, Merkel's discs, and Ruffini's corpuscles
• Pain/temperature sensory receptors


  Signals from skin conveyed by physical change (mechanoreceptors), temperature (thermoreceptors), or pain (nociceptors)
• Pressure sensory receptors


  Mechanoreceptors that respond to mechanical forces, including pressure, vibrations, etc.
• Arrector pili


  Small muscles attached to hair follicles in mammals, cause hair to stand up (goose bumps)
• Hair root plexus


  Special group of nerve fiber endings that serves as a very sensitive mechanoreceptor for touch sensation, forms a network around a hair follicle
• Hair matrix


  Part of the hair follicle, where keratinocytes increase to form the hair shaft of growing hair
• Skin color


  Controlled by the interaction of melanin, carotene, and hemoglobin
• Hair color


  Depends on the distribution, type, and amount of melanin in the middle layer of the hair shaft, controlled by melanocytes in the epithelial layer
• Integumentary system functions


  • Acts as a physical barrier from bacteria, injury, infection, sunlight, and regulates temperature
• Skeletal cartilage


  No blood vessels or nerves, components are ground substance, fibers, and cells, most cartilage is surrounded by the perichondrium
• Types of cartilage and their location

  • Hyaline cartilage - articular cartilage of a joint, costal cartilage, articular cartilage of a joint, cartilages in nose
  • Elastic cartilage - cartilage in external ear
  • Fibrocartilage - cartilage in intervertebral disc, pubic symphysis, meniscus
• Perichondrium


  A dense layer of fibrous connective tissue that covers the surface of most of the cartilage in the body, outer fibrous layer contains fibroblasts, inner chondrogenic layer that contains chondroblasts
• Chondroblasts


  Cells located in the perichondrium that play an important role in the formation of cartilage
• Chondrocytes


  Maintain the extracellular matrix and produce the cartilage matrix