MSK - general Flashcards
5 functions of the skeleton?
Support Protection Movement Mineral storage - Ca & PO4 Produces blood cells
Name the two ways bones develop in utero
Intramembranous ossification → flat bones
Endochidnral ossification → long bones
Which cells are involved at the outset of ossification?
Mesenchymal cells
Outline intramembranous ossification
Mesenchymal cells condense and differentiate into osteoblasts → ossification centre forming
Osteoid is secreted and traps osteoblasts → osteocytes
Trabecular matrix and periosteum form
Compact bones develops
Blood vessels condense to red bone marrow
What cartilage is involved in endochomdral ossification?
Hyaline
What are the primary and secondary ossification centre know as?
Diaphysis
Epiphysis
What are the functions of osteoblasts?
Bone forming
Secrete osteoid
Catalyse minerelisation of osteoid
What is the function of osteocytes?
Sense mechanical strain and dissect osteoblast and osteoclast activity
Where are osteoclasts derived from?
Bone marrow
What are the 2 components of the organic bone matrix?
Type 1 collagen Ground substance (proteoglycans, glycoproteins, cytokines and growth factors)
What does the inorganic bone matrix consist of?
Calcium hydroxyapatite
Osteocalcium phosphate
What type of bone has osteons?
Compact
Explain the structure of osteons and how it supports the function of compact bone?
Few spaces → helps compact bone provide protection and supports and resist forces
Osteons are repeated lamellae surrounding a Haversian canal containing blood vessels, nerves and lymphatic
Volkmans canals traverse these canals
What are lacuane and what connect them?
Small spaces containing osteocytes connect by canaliculi contains ECF
Where is yellow bone marrow found?
Medullary cavity
What is the connective tissue covering of bone?
Periosteum
2 types of bone growth?
Interstitial - increase length
Appositional - increase thickness
Where does interstitial growth happen?
Epiphyseal plate
How does interstitial growth differ between epiphyseal and diaphyseal side?
ES - hyaline cartilage is active and dividing to form cartilage matrix
DS - cartilage calcifies and dies , replaced by bone
How does aposotiitional growth occur?
Ridges in periosteum create groove for blood vessel
Ridges fuse → endosteum lined tunnel
Osteoblasts build new lamellae toward centre of tunnel > osteon
Bone also grows outward from new lamellae
3 types of fibrous joints?
Sutures
Syndesmosis
Interosseous membrane
2 types of cartilaginous joints?
Synchondroses
Symphyses
6 types of synovial joints?
Plane Hinge Saddle Pivot Condyloid Ball and socket
Shoulder vs hip stability?
Shoulder: has shallower socket weaker joint capsule less strong ligaments rotator cuff dependent unstable but very mobile
3 types of muscle?
Smooth
Cardiac
Skeletal
6 different arrangements of muscle fibres?
Unipennate Bipennate Multipennate Triangular Fusiform Parallel
Muscle structure from largest to smallest?
Muscle surrounded by epimysium Fascicles surrounded by perimysisum Myofibres surrounded by endomysium Myofibrils Myofilaments
Outline the structure of a myofibre?
Sarcolemma plasma membrane T tubules Sarcoplasm containing myoglobin and mitochondria Sarcoplasmic reticulum Composed of myofibrils
What are the dark and light banks on myofilaments?
Dark - A band of myosin
Light - I band of actin
What separates sarcomeres?
Z discs
Structure of actin?
Helical
Myosin binding site
Troponinnans tropomyosin
What happens to bands during contraction?
I band become shorter
A band the same
H zone narrows/disappearss
Explains the steps in producing an action potential in muscle
VGCCs open in response to AP Ca2+ enters pre synaptic terminal → exocytosis of vesicles contains Ach Ach diffuses across cleft and binds to Ach receptors → AP in muscle
What breaks down Ach and the NMJ?
Acetylcholine esterase
How is a muscle contraction initiated after the AP reaches muscle?
AP propagates along membrane and down T tubules
Dihydorpyridine receptor in t tubule detects change in voltage
This causes a shape change in the protein linked to ryanodine receptor
The ryanodine receptor calcium channel in sarcoplasmic reticulum opens
Ca released from SR into sarcoplasm
Which receptor detects voltage change in t tubules?
Dihydropyridine receptor
What type of receptor does Ach bind to at the NMJ?
Nicotinic
What happens right after Ach binds to receptor?
Sodium ions enter muscle and potassium leaves
Overall Increased positive charge in muscle fibre → depolarisation
Where do the released calcium ions bind to and what happens next?
Troponin receptors, on actin filaments, change shape
Tropomyosin is moved out the way
Myosin attaches to actin → crossbridges form
What happens to the Calcium in the sacrcoplasm while APs continue?
It is actively transported into SR using ATP
Rate of uptake is <= to release so contraction continues
Explain how the ‘power stroke’ is generated?
Calcium causes troponin to move from tropomyosin which exposes myosin binding site
Charged (ADP) myosin binds to actin
ADP is discharged causing myosin head to pivot
Actin is pulled towards M line
How is the myosin head released and recharged?
ATP binds to myosin causing it to be released
ATP is then hydrolysed in to ADP which provides energy to myosin head and its recharged to its original position
Describe the neural control of muscle contraction
Primary motor cortex - UMN
Synapse with LMN in brainstem or spinal cord
What is a motor unit?
A single motor nerve fibre and all the muscle fibres it innervates
Stimulation of one motor unit causes contraction of all muscle fibres in it
What are the 3 types of motor units and their differences?
Slow (I) - smallest cell bodies, dendritic trees, thinnest axons, slowest conduction velocity | red, high myoglobin, high aerobic, low anaerobic capacity
Fast fatigue resistant (IIA) - high myoglobin, pink, high anaerobic capacity
Fast fatiguable (IIB) - low myoglobin, white, high anaerobic capacity, low aerobic
- larger cell bodies and dendritic trees, thicker axons, faster conduction velocity
How are motor units classsified?
Tension generated
Contraction speed
Fatiguability
How is muscle force regulated? (2)
Recruitment
Rate coding
Explain the recruitment process?
Smaller motor units are recruited first , normally slow twitch
More force = more units recruited
Allows for fine motor control
Explain rate coding.
As motor unit firing rate increases , force produced increases
Slow units fire at lower frequencies
When does summation happen?
When motor units fire at a frequency too high to allow for muscle relaxation between APs
What are neurotrophic factors?
Growth factor that prevent neuronal death and promote growth after injury
What determines motor unit characteristic and how is this known?
The nerve that innervates them
If two different types of motor units are cross innervated they swap characteristics
What are the 3 types of muscle contraction?
Concentric - muscles shorten
Eccentric - muscles elongate , greatest force generated
Isometric - no movement
What causes change from type I to type II fibres? (3)
Severe de conditioning
Spinal cord injury
Microgravity
What occurs to muscle fibres with aging?
Loss of type I and II fibres
Greater proportion of II lost
Slower contraction times
Most common fibre type change?
IIB to IIA from training
Types of bone fractures?
Trauma - high/low energy
Stress - abnormal stress on normal bones
Pathological - normal stress on abnormal bone
Describe how a stress fracture occurs?
Overuse of bone
Stress on bone is greater than its ability to remodel
Bone weakens and stress fracture forms
What is the female athlete triad?
Links to stress fractures
Disordered eating, amennorhea and osteoporosis
Name 6 causes of pathological fractures
Vit D deficiency (osteomalacia or rickets) Malignancy Osteoporosis Osteomyelitis Osteogenesis imperfecta Pagets
Some risk factors for osteoporosis?
Female gender
Postmenopausal women
Senility (>70)
3 causes of secondary osteoporosis?
Alcoholism
Hypogiandisim
Glucocorticoids excess
How does vitamin d deficiency affect bone?
Reduced calcium, magnesium and phosphate absorption
Leads to defect in osteoid matrix mineralisation
Bone is soft and bends in response to stress
Outline osteogenesis imperfecta
Autosomal
Less type 1 collagen → reduced secretion and abnormal collagen produced
Insufficient osteoid production
Name 3 signs associated with OI
Blue sclera
Short stance
Lense dislocation
Outline Paget’s disease
Excessive bone break down
Disorganised remodelling
Leads to bone deformity → pain, fracture, arthritis
What are the 4 stages of Paget’s disease?
Osteoclast activity
Mixed osteoclast osteoblasts activity
Osteoblasts activity
Malignant degeneration
Name 4 primary bone cancers?
Ewing’s sarcoma
Osteosarcoma
Chondrosarcoma
Lymphoma
Secondary bone cancer - different sites of origin and type?
Blastic- prostate
Lytic- kidney, thyroid, lung
Both - breast
What is Wolffs law?
Bone grows and remodels in response to forces placed on it
What are the 3 steps of bone healing?
Bleeding and inflammation
Repair
Remodelling
Soft vs hard callus formation?
Soft callous forms first from type 2 collagen
Converted to hard callous of type 1 collagen
What is primary bone healing and its advantages?
Intramembranous healing
Gives most stability
Direct to woven bone
What is secondary bone healing?
Endochomdral healing
Relative stability
More callous because if endochondral ossification
What are the 3 steps to fracture management?
Reduce
Hold
Rehabilitate
what are the different types of reduction?
Open: small incision or full exposure
Closed : manipulation or traction (skin or skeletal)
What are the types of hold?
Closed with plaster or traction
Fixation
What are the different fixation options?
Internal - intramedulalry (pins or nails) or extramedullary (plate and screws or pins)
External - mono or multiplanar
What are the steps in rehabilitation?
Use
Move
Strengthen
Weight bear
What is the difference between tenidnosis and tendinitis?
Abnormal thickening
Inflammation
Outline the 3 grades if ligament injury
I : slight tear, no instability
II: more severe incomplete tear, some instability
III : complete tear, very unstable, surgery
What are the options for ligaments and tendon repair?
Immobilise with plaster or boot/brace
Surgery with sutures
