RJ EdwardsLab 4: Cartilage and Bone

Histology Notes9/7/16

Hyaline Cartilage

  • Glassy, intensely staining matrix, may show metachromasia
  • Individual chondrocytes within lacunae. May be torn from section
  • Isogenous nests of 2-8 chondrocytes = interstitial growth
  • Perichondrium = surrounded by several layers of chondroblasts = appositional growth
  • Territorial matrix = very dark matrix immediately surrounding lacunae
  • Interterritorial matrix = lighter staining matrix between lacunae
  • Avascular: no blood vessels inside cartilage, or perichondrium.
  • Found in joints, ribs, nose, trachea and bronchi.
  • Scaffold for bone formation = calcification

Elastic Cartilage

  • You will not be expected to distinguish elastic and hyaline cartilage
  • Contains elastic fibers = matrix looks reticular.
  • Chondrocytes closer together, less matrix
  • Fewerisogenous nests than hyaline (but some still present)
  • Found in ear, Eustachian tubes, and epiglottis
  • See U Mich slides:

Fibrocartilage

  • Part of continuum: dense regular CT → fibrocartilage → hyaline cartilage
  • Fibrous CT with lacunae
  • Lacunae arranged in rows, not nests
  • Mixture of chondrocytes and fibroblasts
  • No perichondrium
  • Connects ligaments & tendons to bone
  • Present in intervertebral disks, pubis symphysis, sterno-clavicular joint, temporomandibular joint
  • Repairs damaged elastic or hyaline cartilage

Bone

  • Periostium = DICT covering, fibroblasts → osteoprogenitor cells or periosteal cells
  • Compact, dense –vs– spongy, cancellous, trabecular
  • Three cell types: osteoclasts, osteoblasts, osteocytes

o–clasts consume

  • large, multinucleate
  • found in Howship’s lacunae

o–blastsbuild

  • squamous (inactive, bone lining cells) to cuboidal (active osteoblasts)

o–cytes live in lacunae

  • Osteons in mature, compact bone

oConcentric lamellae

oHaversian canals

oRadial canaliculi

oVolkmannscannals

  • Bone marrow = medullary cavity

oCords of hematopoietic cells

oVenous sinusoids

oRed/Yellow marrow

  • Bone formation:

oEndochondral = calcify cartilage scaffold = most bones

oIntramembranous = no cartilage = skull, mandible, clavicles

oEpiphyseal growth plate (long bones)

  • Reserve cartilage
  • Zone of proliferation
  • Zone of hypertrophy
  • Zone of calcification

Vocabulary

Interstitial vs appositional (growth)

Epiphysis, diaphysis, metaphysis

Periosteum, endosteum

Osteoblast, osteocyte, osteoclast

Perichondrium

Chondroblast, chondrocyte

Lacuna

Hyaline

Trabeculum/trabeculae (n), trabecular (adj)

Metachromasia

Look-alikes

  • Hyaline cartilage vs bone (demineralized, not ground)

oBoth have uniform matrix with lacunae

oSingle cells in lacunae = bone

oIsogenous nests = cartilage

oNo blood = cartilage

oMarrow + venous sinusoids = bone

  • Osteoclasts vs Megakaryocytes

oMegakaryocytes probably won’t be on exam, osteoclasts probably will

oLocation: Marrow (MKC) vs edge of bone (OC)

oNucleus: Large, lobed, single nucleus (MKC) versus polynucleate(OC)

oCentral nucleus (MKC) versus nuclei at one side (OC) = polarized cell

oMay see signs of perforations (MKC)