Chapter 5

• Cartilage


  chondrogenic cell --> chondroblasts --> chondrocytes --> cartilage
• Perichondrium


  contains fiber layer and chondrogenic layer
• Fiber layer


  consists of fiberblasts
• Chondrogenic layer


  consists of chondrogenic cells
• Chondrogenic cells


  make chondroblasts

  found in chondrogenic layer in perichondrium
• Chondroblasts


  secrete matrix

  make chondrocytes
• Chondrocytes


  found inside cartilage

  undergo mitosis
• Lacuna 


  outer area of chondrocyte
• isogenous groups


  lacuna with two chondrocytes: mid mitosis
• Territorial matrix 


  matrix around the lacuna
• Interterritorial matrix 


  matrix inside cartilage

  older "territorial matrix"
• Interstitial growth


  growth of cartilage from the inside through mitosis of chondrocytes
• Appositional growth


  growth of cartilage from the outside through layering of chondroblasts
• 3 types of cartilage

  1. hyaline
  2. elastic
  3. fibrocartilage
• Hyaline cartilage 


  has perichondrium

  used to form embryonic skeleton

  found in nose, ribs, end of long bones, sternum
• Articular cartilage


  resembles hyaline

  no perichondrium

  nourished by synovial fluid (no blood)
• Elastic cartilage


  type II collagen + elastin

  found in ears and vocal cords
• Fibrocartilage


  type I and III collagen

  resembles dense regular CT but has chondrocytes

  will not see distinct perichondrium
• Bone

  osteoprogenitor cells --> osteoblasts --> osteocytes
• Osteoprogenitor cells


  derived from mesenchyme

  like chondrogenic cells
• Osteoblast


  make osteocytes

  like chondroblasts
• Osteoid


  bone matrix

  gets calcified by calcium hydroxyapatite
• Osteocytes


  mineralized by calcium

  no mitosis

  dormant in lacunae
• Canaliculi 


  tunnels by which nutrients are shared throughout bone
• Osteoclasts


  eat up broken bone

  like macrophages
• Howship's lacunae / resorption bay


  hole in matrix made by osteoclast
• Periosteum


  surrounds the bone

  fibrous layer: fibroblasts

  cellular layer: osteoclasts
• Sharpey's fibers


  type I collagen

  weaves together periosteum and circumferential lamellae
• Haversian canals


  middle of an osteon
• Concentric lamellae


  layers of the osteon
• Circumferential lamellae


  layers of the bone

  weaved into periosteum
• Volkmann's canals


  osteon to osteon

  in and out of periosteum and endosteum

  transports blood/nutrients through compact bones
• bone marrow types

  1. yellow: fats
  2. red: source of new RBC
• Trabecula 


  strands of bone

  contains hematopoietic stem cells
• Irregular lamellae

  layers found in spongy bone
• Intramembranous ossification


  forms either in mesenchymal membranes or periosteum

  1. at primary ossification, mesenchymal cells form osteoblasts (woven)
  2. osteoclasts eat woven bone and osteoblast makes lamellae bone
• Endochondral ossification


  forms mostly in hyaline cartilage

  expanding from the inside of the bone in all different directions
• Primary center of ossification


  in the middle of the bone
• Bony collar


  inside of the perichondrium

  on the side of the primary ossification center
• Periosteal buds


  penetrate the periosteum and bone to fill marrow cavity with nutrients