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44 Cards in this Set

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What are the 5 Functions of Bone?
1. Supporting and protecting soft tissues
2. Attachment site for muscles (making movt possible
3. Storage of minerals
4. Blood cell production (RBM haemopoiesis)
5. Energy storage (YBM)
What are the major components of a long bone?
Diaphysis -shaft
epiphysis - one end of long bone
metaphysis - growth plate region
articular cartilage - friction and shock absorber
medullary cavity - marrow cavity
endostium - lining of marrow cavity
periostium - tough membrane covering bone but not cartilage
What is periostium?
tough membrane covering bone but not cartilage
Fibrous layer of dense irregular connective tissue
Osteogenic layer = bone cells and blood vessels that nourish or help with repair
What bones make up the axial skeleton?
Skull, vertebral column, ribs
What bones make up the apendicular skeleton?
Pectoral girdle, pelvic girdle, upper limbs, lower limbs
What is the histology of bone?
Connective tissue. Has widely space cells separated by matrix.
4 types of cells - osteogenic cells, osteoblasts, osteocytes, osteoclasts
Matrix composed of 25% water, 25% collagen, 50% crystalised minerals
What 4 cell types make up bone?
Osteogenic cells (osteoprogenitor) - undifferentiated
Osteoblasts - form bone matrix
Osteocytes - mature bone cells
Osteoclasts - fused WBC, bone resorption
What makes up bone matrix?
Inorganic mineral salts - hydroxyapatite and organic collagen fibres.
What are the histological features of dense / compact bone?
Dense bone is composed of osteon - concentric rings (lamellae) of calcified maxtrix surrounding vertically oriented blood vessel. Matrix laid down by osteoblasts. Osteocytes found in spaces between the lamella called lacunae. Osteocytes communite through canliculi filled with extracellular fluid. Interstitial lamellae represent older osteons that have been partially removed during tissue remodelling
What are the histological features of spongy bone?
Found at end of long bones and inside flat bones. Latticework of thin plates called trabecula (oriented along stress lines), spaces between thees are filled with RBM.
blood and nerve supply of bones
Periosteal arteries - supply periostium
Nutirent arteries - enter via foramen, supply compat bone of diaphysis and RBM
Metaphyseal and epiphyseal arterier - supply
Describe 2 types of Bone formation?
Begins from mesoderm cells (mesenchyme)
Can form in one of 2 ways
Intramembranous bone formation - flat and irregular bones from directly from mesenchymal cells
Endochondrial bone formation - long bones from within hyaline cartilate
Outline the steps for intramembranous bone formation?
1 Mesenchyme cells become osteoprogenitor cells then osteoblasts
2 Osteoblasts surround themselves with matrix
3 Matrix calcifies into trabeculae with spaces holding RBM
4 Mesenchyme condenses into the outer periostium
5 Superficial layers of spongy bone are replaced with compact bone.
Used for flat and irregular bones
Outline endochrondrial bone formation
1) development of cartilage model, growth of cartilage model
2) calcification of the cartilage model
3) ossification
4) Osteoblasts from periosteal bud deposit bone matrix over calcified cartilagge forming spongy bone trabeculae. Osteoclasts form medullary cavity.
5) Development of secondary ossification centre
6) Formation of articular cartilage
used for formation of long bones
Bone growth in length stops at age ____
Bone growth in length stops at age 25
Epiphyseal plates close at age ____
Epiphyseal plates close at age 18 - 25
What are the zones of growth in epiphyseal plates
zone of resting cartilage
zone of proliferating cartilage
zone of hypertrophic cartilage
zone of calcified cartilage
Bones grow in width by _______ growth
Bones grow in width by appositional growth
What are the factors affecting bone growth and remodelling?
1. Nutrition
vit A simulates osteoblasts, calcium and phosphorus for bone growth, Vit C for collagen, Vit K and B12 for protein synthesis
2. Sufficient levels of hormones (T3 and T4, hGH, insulin, sex steriods at puberty)
Outline the 4 steps in fracture repair
1) formation of fracture haematoma
2) formation of fibrocartilagenous callus
3) formation of bony callus (last 3-4 months)
4) bone remodelling
What are calcium ions needed for?
nerve conduction
Muscle contraction
Blood clotting (factor V)
What occurs is Calcium ion levels fall too low (<9mg/100mg)
Parathyroid hormone (PTH) is secreted. Osteoclast activity increased, Kidney retain Ca2+ and produces calcitriol
What occurs is Calcium ion blood levels are too high (>9mg/100mg)
Calcitonin is secreted from parafollicular cells in thyroid gland. Inhibits osteoclast activity, increases bone formation by osteoblasts.
What are the 3 types of muscle cells
1. skeletal
2. cardiac
3. smooth
What are the 5 functions of muscle tissue
1. body movements
2. Stabilise body positions
3. Regulating organ volumes
4. Movement of substances within the body
5. Production of heat
What are the 5 properties of muscle tissue?
1. Excitability
2. Extensibility
3. Elasticity
4. Contractability
5. Conductivity
Outline the process of contraction
1. ATP hydrolysis
2. attachment of myosin to acting forming cross bridges
3. Power stroke
4. Detachment of myosin from actin.
what is a sarcolemma?
Muscle cell membrane
What is sarcoplasm?
Cytosol
What is a myofibril?
The threads which fill muscle fibres. They are separated by SR. Mitochrondira lie in rows between the myofibrils throughout the cell.
What is a transverse tubule?
Invaginations of the sarcolemma which carry the muscle action potential into the cell
What is sarcoplasmic reticulum?
Similar to smooth ER. Store Ca2+ ions in a relaxed muscle. Release of Ca2+ triggers muscle contraction
What is a myofilament?
The threads which fill a myofibril. They contact contractile proteins of the muscle (thick and thin filaments)
What are the proteins in a myofibril?
1. Contractile proteins - myosin and actin
2. Regulatory proteins which turn contraction on and off - troponin and tropomyosin
3. structural proteins - titin, myomesin, nebulin, dystrophin
What is a thick filament?
a protein made up of myosin. Held in place by M line proteins
What is a thin filament?
A protein made up of actin, troponin and tropomyosin.
They are held in place by Z lines (one Z line to the next is a sarcomere)
What is the relationship between actin and tropomyosin?
each actin molecule has a myosin binding site. Tropomyosin covers the binding site. In the presence of Ca2+ the tropomyosin turns to reveal the myosin binding site.
Describe the sliding filament mechanism of contraction?
Myosin cross bridges pull on thin filaments
Thin filaments slide inwards
Z discs come toward each other
- sarcomeres shorten, the muscle fibres shorten, the muscle shortens
How does muscle contraction begin?
1.Nerve impulses reach an axon terminal and synaptic vesicles realse acetylcholine (ACh).
2. ACh diffuses to receptors on the sarcolemma and Na+ channels open and Na+ rushes into the cell (depolarisation)
3. A muscle action potential spreads over sacrolemma and down into the transverse tubules.
4. SR releases Ca2+ into the sarcoplasm
5. Ca2+ binds to troponin and causes troponin and trypomyosin complex to move and reveal myosin binding side on actin.
How do muscles relax?
AChE (acetylcholinesterase) breaks down ACh within the synaptic cleft.
Muscle action potential ceases.
Ca2+ release channel closes
Calcium binding protein helps hold Ca2+ in SR
Tropomyosin-troponin complex recovers bind site on the actin
What is NMJ?
The connection between the nervous system and the muscular system. End bulbs contain ACh, motor end plate contains 30 million ACh receptors.
What is isotonic contraction?
a load is moved. Muscle shorten to produce movement
What is isometric contraction?
No movement occurs. Tension is generated without muscle shortening.
What are the 3 classifications of muscle fibres?
Slow oxidative (slow twitch) prolonged
Fast oxidative-glycolitic (fast twitch A) sprinting
Fast glycoltic (fast twitch B) weight lifting