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Flashcards in bones XXXXXXXXXXXXXXXXXXXX Deck (15)
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1
Q

what are the functions of a bone?

A
  • Weight bearing/support
  • Protection (e.g. skull: brain, vertebrae: spinal cord)
  • Mineral store
  • Blood formation (red bone marrow)
2
Q

Gross anatomy of bones

A
  • Compact bone
  • Spongy (trabecular) bone
  • Blood vessels
  • Medullary cavity
  • Bone marrow
  • Membranes

–Periosteum

–Endosteum

3
Q

Osteons/Haversian systems

A
  • Compact bone organised in circular structures (osteons/Haversian systems)
  • Central/vertical Haversian canal and horizontal perforating/Volkmann’s canals
  • Osteocytes and concentric rings of bone matrix (lamellae) around Haversian canal
4
Q

what are the componts of Osteons?

A
5
Q

what is a spongy bone?

A
  • Also called cancellous or trabecular bone or diploe
  • Less dense than compact bone
  • Network of lamellated trabeculae filled with bone marrow (no Harversion systems!)
  • Orientation of trabeculae reflect main directions of mechanical forces
6
Q

name the different types of bones?

A
7
Q

name the two types of bone formation?

A
  • Endochondral (most common type incl. long bone growth)
  • Intramembranous (flat bones of skull, mandible, maxilla, clavicles
8
Q

outline Endochondral ossification?

A
  • Bone forms as cartilage ‘model’ first
  • Blood vessels invade cartilage
  • Cartilage replaced with bone
  • Cartilage remains in epiphyseal growth plate
  • Growth plate eventually ossifies
9
Q

outline the process of Intramembranous ossification?

A
  • No cartilaginous phase!
  • Mesenchymal cells develop into osteoprogenitor cells that mature into osteoblasts that start depositing bone
  • Residual mesenchymal cells develop blood vessels & bone marrow
  • This bone formation also occurs in adult cortical bone
10
Q

What makes up bones?

A

Cells

  • Osteoblasts
  • Osteocytes
  • Osteoclasts

Extracellular matrix

  • hydroxyapatite crystals
  • Collagen (Type I)
  • Water
11
Q

what are the functions of minerals and collagen?

A

Minerals (hydroxyapatite)

  • Make bone stiff & able to support structures
  • High strength under compression (like concrete)

Collagen

  • gives bone some flexibility & reduces risk of fracture
  • High strength under tension (like steel)
12
Q

Outline the process of Bone turnover/remodelling?

A
  • Constant process even in adult bone
  • Healthy bone: Balance between bone removal & formation
13
Q

what are Osteoblasts?

A
  • Immature bone cells created from osteopregenitor cells in periosteum & endosteum
  • Function: produce bone matrix (unmineralised matrix = osteoid) & initiate calcification
  • Become osteocytes once surrounded by matrix
14
Q

what are Osteocytes?

A
  • Mature bone cells found inside lacunae
  • Numerous processes lying in canaliculi
  • Canaliculi connect lacunae to each other à allows communication between cells
  • Function: not well understood, may maintain bone matrix & sense mechanical forces
15
Q

what are osteoclasts?

A
  • Multinucleate cells derived from monocytes/macrophages
  • Found on bone surface
  • Large cells with ‘ruffled border’
  • Function: resorb bone matrix

Bone reabsorption: the process by which osteoclasts break down the tissue in bones and release the minerals, resulting in a transfer of calcium from bone tissue to the blood