4 - bone Flashcards
1
Q
functions of skeleton
A
- Support
- Movement
- Protection
- CALCIUM HOMEOSTASIS - constant exchange between blood + bone - nerve conduction + muscle contraction
- Storage of red + yellow marrow
2
Q
5 classifications of bone
A
- Long - tubular bones - limb bones
- Short - ankle (tarsals) + wrist (carpals) bones
- Flat - usually for protection - cranial bones
- Sesamoid - bones embedded into tendons - tendons cross ends of long bones to protect + change angle of tendon
- Irregular - bones are all different shapes - face
3
Q
structure - general
A
- Epiphysis - ends of long bone - articular surface
- Metaphysis - between epiphysis + diaphysis - contains epiphyseal (growth) plate
- Diaphysis - long straight section
4
Q
structure - out to in
A
- Articular cartilage - on epiphysis
- Periosteum
- Compact bone
- TRABECULAR BONE
- Endosteum
- Medullary cavity
5
Q
periosteum
A
- Tough, VASCULARISED fibrous sheath that superficially covers bone where no cartilage exists
- Nourishes bone
- Protects bone
- Attachment point for ligaments + tendons
- Deep layers have osteogenic ( bone forming) cells for bone REPAIR
6
Q
endosteum
A
- Thin membrane lining medullary cavity
- Single layer of bone-forming (osteoprogenitor) cells
7
Q
medullary cavity
A
- Stores bone marrow
- Minimises weight of bone
8
Q
compact bone
A
- Solid, dense bone
- Repeating structural unit - osteon
- Makes up most of diaphysis
- -protection + support
9
Q
trabecular / spongy / cancellous bone
A
- Porous bone w/ interconnecting trabeculae
- Interior of bone
- Core of epiphysis in long bones
- Makes up majority of short, flat, irregular, sesamoid bones
10
Q
woven bone
A
- Immature bone
- Random arrangement of collagen fibres
- Formed during foetal development + fracture repair
- Remodelled into lamellar bone
11
Q
lamellar bone
A
- mature bone
- Concentric bands of collagen
- Fibres are oriented in one direction in each layer - but each layer is in different direction - increase in strength
12
Q
organic matrix
A
- Dry weight 35%
- Type 1 collagen
- Contains proteoglycans + glycosaminoglycans
- Contains glycoproteins (oligosaccharide chains covalently attached to amino acid side chains)
- osteonectin + osteocalcin
13
Q
inorganic matrix
A
- Dry weight 65%
- Composed of CALCIUM PHOSPHATE = HYDROXYAPATITE
- Hardness, compressive strength
14
Q
points to note re: bone
A
- Bone is an organ
- Bone is metabolically active
- Highly vascularised ( unlike cartilage)
- Constantly being remodelled - osteoclasts + osteoblasts
15
Q
compact bone structure
A
- Also known as Haversian system - functional unit consisting of concentric lamellae (thin layers of tissue)
- Lacunae - spaces between concentric lamellae
- Canaliculi - small extracellular fluid channels radiating from lacunae
- Haversian canal - neurovascular channels
- Osteonic and Perforating canals - provide blood vessels + nerves from periosteum
16
Q
trabecular bone structure
A
- Latticework of thin plates of bone called trabeculae - oriented along lines of stress
- Spaces in between struts are filled with red marrow
- Found in ends of long bones + inside flat bones such as hip bones , sternum , ribs
17
Q
osteoprogenitor cells
A
- pre-osteoblasts
- Derived from mesenchymal stem cells
- Found along inner portion of periosteum , endosteum , blood vessels in bone
- Only bone cells to undergo MITOSIS
18
Q
osteoblasts
A
- bone forming cells
- Synthesise and secrete collagen - osteoid formation
- Initiate calcification
- Found lining bone
- Become trapped in matrix? + turn into osteocytes
19
Q
osteocytes
A
- Mature bone cells
- Maintain bone metabolism
20
Q
osteoclasts
A
- bone resorbing cells
- Large, multinucleated cells
- Derived from fusion of monocytes
- Concentrated in the endosteum
- Active osteoclasts sit in depressions
- Release enzymes for bone resorption
- Ruffled border on side that faces bone border
21
Q
intramembranous ossification
A
- Ossification within a membrane - 8 weeks
- Mesenchyme cells secrete protein matrix that later mineralizes (becomes hard)
- primarily flat + irregular bones - skull, face
22
Q
endochondrial ossification
A
- The replacement of cartilage by bone
- Mesenchyme turns into cartilage that is later replaced by bone
- Majority of bones
- Normally associated w/ growth in length eg. Humerus, femur
23
Q
intramembranous ossification process
A
- Mesenchymal stem cells differentiate into osteoprogenitor cells then osteoblasts
- Osteoblasts surround themselves in bone matrix
- Bone matrix is calcified into trabeculae with spaces for red marrow in between
- Periosteum develops
- Outer layers of spongy bone are replaced w/ compact bone
24
Q
epiphyseal growth plate
A
- Zone of resting cartilage - consists of small scattered chondrocytes
- Zone pf proliferating cartilage - consists of larger chondrocytes arranged like coins
- Zone of hypertrophic cartilage - large maturing chondrocytes
- Zone of calcified cartilage - dead chondrocytes in calcified cartilage
- osteoclasts dissolve cartilage
- osteoblasts + capillaries invade the area
25
Q
bone remodelling
A
- Bone forms before birth but continually renews after its formation
- Old bone is resorbed by osteoclasts
- Replaced with new osteoid, secreted by osteoblasts
- Renewal rate for compact bone - 4% every year
- Renewal rate for trabecular bone - 20% every year
- Replace the whole skeleton every 7-10 years
26
Q
achondroplasia
A
- without cartilage formation
- Affects endochondral ossification
- Closure of epiphyseal plate before bones mature + normal bone length is reached
- All people with achondroplasia have short stature
- Bones derived from intramembranous ossification not affected
CHARACTERISTIC FEATURES
- Short upper arms + thighs
- Limited range of motion at elbow
- ENLARGED HEAD W/ PROMINENT FOREHEAD
- Fingers typically short + ring finger + middle finger might diverge, giving the hand a three pronged appearance
