Bone Tissue + Structure Flashcards
Two extra cellular components of bone:
- Organic
- Inorganic
(Makes up 98% of bone weight)
Organic Extra cellular component: is made up of
33% of bone matrix is organic
- Collagen (protein)
- Ground substance (proteoglycans)
- Function = resists tension ( without collagen the bone is brittle - breaks easily )
Inorganic extracellular component
67% of bone matrix is inorganic
- Hydroxyspatite + other calcium minerals (mineral salts)
- Mineral component makes bone hard and resistant to compression
Cellular bone component:
Makes up 2% of bone weight
- Osteogenic cells
- Osteoblasts
- Osteocytes
- Osteoclasts
Together these cells maintain bone homeostasis
- balance of bone destruction and formation means amount of bone stays the same
What do the 4 cellular bone cells do
Osteogenic cells: stem cells that produce osteoblasts
Osteoblasts: makes, produces new bone
Osteocytes: maintains + communicates - recycle minerals + proteins from matrix - control activity of osteoblasts + Osteoclasts - destroyers - remove bone matrix
Two types of bones and how they are related/ different:
- compact = osteon structure
- cancellous = trabecula structure
Made up of the same things (ECM + cells) but structured differently
Compact bone macro + microscopically
Microscopically:
- outer surfaces seem dense + impenetrable (periosteum)
- formamina (holes) for blood supply
Microscopically:
- made up of circumferential lamellae and units called osteons
Osteon Definition
Longnatudinal (lengthwise) unit within compact bone
- provides a pathway for nutrients to get to cells in ECM
Central Canal Definiton
Contains blood vessel and nerves
Lamellae
A series of cylinders of ECM formed around a central canal.
- Forms shape of osteon
- Collagen fibres within lamellae resist forces
Lacunae
Lakes for osteocytes
Canaliculi
Channels for nutrients through ECM
Cancellous bone structure
Trabeculae
- Struts of lamella bone
Marrow fills cavities between trabeculae
Osteocytes housed in lacuna in between lamellae/on surface
Why trabeculae oriented in certain ways
- Organisation of trabeculae resists force from multiple directions
- Directs force from body weight in single direction down shaft
- Spreads force distally
Pelvic girdle force distubution
- trabeculae channel weight areound ilia into femora
- spreading force distally
Bone Remodeling
Allow bones to grow - appositional growth
- Osteoblasts add bone matrix in lamellae to bone surface
- Osteoclasts remove bone from medullary cavity
Allows bone to respond plastically
Shape change is possible through life to resist strain
Bone homeostasis
Balance of OB and OC activity
Bone is constantly being formed/destroyed
Allows body to mobilise minerals from the bone matrix
Name for OC > OB activity
Osteoporosis and osteopina
Osteoporosis
- cancellous bone - trabeculae become thinner
- compression fractures of vertebrae
Why only some people get osteoporosis
- Women more at risk due to loss of estrogen post-menopause
- Life style factors such as lack of exercise and nutrition factors
- Depends on start point, peak bone mass In 20’s, ideally needs to be high
WHAT ARE YOU SACRAFISING
STABILITY OR MOBILITY
Is bone dead or living tissue
Living tissue ALIVE
Osteocytes vs Osteoblasts which is mature or immature
CYTES is mature
3 types of lamellae
Concentric - canal
Interstitial - inbewtween
Circumferential
How does the arrangement of blood vessels differ between compact and cancellous bone
- different because of different properties of the bone
- cancellous bone has more surface area with spaces between trabeculaw filled with bone marrow and vessels.
- compact bone is made of osteons tightly packed together so blood vessels are in the central canal of each osteomyelitis,
How does the presence of an epiphyseal growth plate relate to linear growth of the long bones?
The growth plate is the place where new bone is added to the ends of the shaft during growth, allowing the bone to grow longer before the epiphysis is fused to it.
Why are vertebrae most effected by osteoporosis
vertebrae are particularly susceptible to compression fractures.
