structure of bone tissue

Question 1

Structure of bone tissue

Answer 1

• Supporting connective tissue
• Contains specialised cells

Comprised of organic + inorganic components
- Specialised cells produce a solid matrix of calcium salt deposits (inorganic) around collagen fibres (organic)

Question 2

Bone matrix

Answer 2

• Around 70% of bone is made up of a bone mineral called hydroxyapatite (inorganic)
• Around 30% of the bone matrix is comprised of collagen fibres (organic)
• The hydroxyapatite accumulates around the collagen fibres to make them hard

Question 3

Bone Cells

Answer 3

• Make up only 2% of the mass of a bone!
• Four types of bone cells
  1. Osteoprogenitor cells (first cell that will slipt/morph into other cells)
  2. Osteoblasts
  3. Osteocytes
  4. Osteoclasts

Question 4

Osteoprogenitor cells

Answer 4

• stem cells that divide to produce osteoblasts
• Located in endosteum + the inner cellular layer of periosteum
• Assist in fracture repair

Question 5

Osteoblasts

Answer 5

• Immature bone cells that secrete matrix compounds (process called osteogenesis)
• Osteoid: immature bone = matrix produced by osteoblasts, but not yet calcified to form bone
• Osteoblasts surrounded by bone become osteocytes

Question 6

Osteocytes

Answer 6

• Mature bone cells that maintain the bone matrix
• Live in lacunae (spaces) that provide nutrients
• Are b/w layers (lamellae) of matrix
• Long processes of the osteocyte lie in the canaliculi
• Two major functions of osteocytes
  1. To maintain protein + mineral content of matrix
  2. To help repair damaged bone

Question 7

Osteoclasts

Answer 7

• Derived from stem cells in bone marrow that produce macrophages
• Giant, multinucleate cells
• Secrete acids + protein-digesting enzymes
• Dissolve bone matrix + release stored minerals (osteolysis) so …..
• Important for growth + repair + remodelling of bone after injury

Question 8

Bone homeostasis (steady state)

Answer 8

• Bone building (by osteoblasts) + bone breakdown (by osteoclasts) must balance
• More breakdown than building → bones become weak
• Exercise, particularly weight-bearing exercise + heavy loading causes osteoblasts to build bone