bones XXXXXXXXXXXXXXXXXXXX Flashcards
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
