integumentary system

• functions of integumentary system


  protection

  thermoregulation

  sensation

  immunity

  vitamin d synthesis
• 3 skin layers

  epidermis

  dermis

  hypodermis
• hypodermis is also commonly known as the ...

  superficial fascia
• the subcutaneous layer of the skin is mostly made up of --- tissue.

  adipose

  subcutaneous fat
• the epidermis is keratinized simple squamous epithelial.
• the dermis is mostly dense irregular connective tissue.
• the hypodermis is made up of areolar and adipose connective tissue.
• four epidermal appendages

  epidermal pegs

  skin glands

  hair follicles

  nails
• four types of epidermal cells

  keratinocytes

  melanocytes

  langerhans cells

  merkel cells
• keratinocytes


  make keratin fibers

  main cells in epidermal
• melanocytes


  pale staining

  derived from neural tissue

  found in stratum basale

  make melanin in melanosomes
• melanosomes


  found in cytoplasms of keratinocytes

  stratum basale and spinosum
• melanin is found near the nucleus, closest to the surface. (protects the nucleus from UV radiation)
• langerhans cells

  dendritic cells

  antigen presenting cells

  originate in bone marrow

  dark staining nucleus

  pale cytoplasm

  abundant in stratum spinosum
• merkel cells


  mechanoreceptors

  epithelial tactile cells

  found in stratum basale of fingertips and oral mucosa

  indented nuclei

  best seen in electron micrographs
• five epidermal layers

  stratum corneum

  stratum lucidum

  stratum granulosum

  stratum spinosum

  stratum basale
• stratum basale


  stratum germinativum

  epidermal stem cells

  undergo mitosis

  push old cells to surface

  composed of cuboidal to low columnar cells
• stratum spinosum

  thickest layer

  desmosomes look prickly
• function fo desmosomes


  attach adjacent cells in the stratum spinosum
• stratum granulosum

  keratohyalin granules

  dark staining

  extracellular ceramides and lipids with pyknotic nuclei

  makes epidermis waterproof
• stratum lucidium


  cells losing nuclei

  accumulated keratin

  only seen in thick skin
• stratum corneum


  dead flattened anucleate cells

  abundant keratin
• what is the mnemonic for the layers of the epidermal?

  come let's get sun burnt
• thick skin is found ...

  on palms of hands and soles of feet
• what cells are found in the dermal layer?

  fibroblasts (most abundant)

  mast cells

  macrophages

  leukocytes

  adipocytes
• dermal layers


  papillary

  reticular
• papillary layer 


  loose CT

  dermal papillae

  dermal ridges

  dermatoglyphs
• dermal papillae


  has capillary loops

  tactile receptors called Meissner's corpuscles
• dermatoglyphs


  fingerprints

  dermal ridges on palm and soles
• reticular layer

  vascular

  dense irregular CT

  majority of the dermis

  large blood vessels, nerves, epidermal appendages

  pacinian corpuscles
• multicellular exocrine glands

  eccrine sweat glands

  apocrine sweat glands

  sebaceous glands
• eccrine sweat glands


  secrete smaller amounts of sweat

  more numerous

  watery secretions: cooling effect

  simple cubodial epithelium

  small lumen
• apocrine sweat glands


  secrete large amounts of sweat

  axillary and groin regions

  lumen is wider

  secretions more viscous
• sebaceous glands


  secrete sebum
• meissner's copuscles


  found in papillary layer
• pacinian corpuscles


  found in reticular layer and hypodermis
• arteriovenous anastomoses


  allow blood to flow directly from arterioles to venules without passing capillaries

  open = cold = limit heat loss

  close = hot = more blood flow to surface
• vellus hair


  shorter

  peach fuzz
• terminal hairs


  longer

  thicker
• hair follicle


  entire structure of the hair