MSK III Flashcards
How does CKD cause osteomalacia?
Reduced phosphate excretion and inactive activation of vitamin D results in secondary hyperparathyroidism with subsequent osteomalacia, sclerosis of bone and calcification of soft tissues
Shepherd’s hook deformity =
Fiberous dysplasia
Where does fiberous dysplasia typically affect?
Proximal femur
Which malignant primary bone tumour tends to occur in abnormal bone?
Fibrosarcoma
Briefly describe the steps involved at the NMJ
- Resting potential of end bulb is negative
- AP coming along makes it positive
- This opens up voltage gated calcium channels, and calcium flows into the end bulb
- This causes vesicles containing ACh to release ACh into the synaptic cleft
- This causes activation of Na channels on the muscle, causing Na influx
- This generated an AP in the skeletal muscle
Describe the process of sliding filament theory
- An AP from the NMJ propagates along the sarcolemma, and down T tubules
- This causes opening of voltage gated Ca channels, and Ca2+ flows out of the terminal cisternae
- Ca2+ bind to troponin, causing tropomyosin to unwind and the myosin binding site on actin to become free
- ATP binds to the myosin, and myosin binds to actin
- Myosin pulls actin towards the M line of the sarcomere
Name and briefly describe the three types of skeletal muscle fibre
Type 1 - Slow contracting - Abundant mitochondria - Resistant to fatigue - Produce relatively less force Type IIA - Intermediate between the other two - Fast contracting - Resistant to fatigue - Uncommon Type IIB - Fast contracting - Few mitochondria - Fatigue relatively easily - Produce relatively greater force
Which type of bone does not contain Haversian canals?
Trabecular (cancellous)
What is the difference between lamellar and woven bone?
Woven is layed down after trauma in a hap hazard fashion
Woven bone is remodelled to lamellar bone
Lamellar bone has collagen fibres all running in one direction
What is the basic multicellular unit (BMU) in bone?
The collection of osteoclasts and osteoblasts that participate in bone remodelling
What is the functional unit of bone?
Osteon
What are each of the following
- A band
- I band
- H zone
- M line
- A band - runs the length of thick filaments (remember A band is dArk)
- I band - runs the length of thin filaments (remember I band is thIn)
- H zone - lighter area within middle of A band, where thin filaments don’t reach
- M line - extends vertically down middle of A band
In skeletal muscle contraction, what is the contractile component and what is the series-elastic component?
Contractile component = sarcomeres
Series-elastic component = connective tissue + tendon
What are the two types of skeletal muscle contraction
Isotonic contraction: -
- Used for (1) body movements and for (2) moving objects
- Muscle tension remains constant as the muscle length changes.
Isometric contraction:
- Used for (1) supporting objects in fixed positions and for (2) maintaining body posture
- Muscle tension develops at constant muscle length
When are each of the skeletal muscle fibre types used?
Type I (slow oxidative) - maintenance of posture, walking Type II (fast oxidative) - jogging Type II (fast glycolytic) - jumping
What are muscle spindles?
Sensory receptors for stretch reflex
They are a collection of specialised muscle fibres
Found in the belly of muscles and run parallel to ordinary muscle fibres
They have their own efferent nerve supply
Why do muscle spindles have their own nerve supply?
To adjust their sensitivity so that they remain sensitive to stretch
What are the four broad types of collagen and where are they found?
Type I - bone, fascia, dermis of skin
Type II - cartilage (hyaline)
Type III - skin, vessels, granulation tissue
Type IV - basement membrane -> important in Alport syndrome
What should you treat MRSA with?
Vancomycin
Asymmetrical huge joint swelling which isn’t as painful as it looks = ?
Lyme disease
Tennis shoe on, step on a nail = ?
Pseudomonas
Needle lickers bug = ?
Eikenella corrodens
Bugs in Sickle cell osteomyelitis?
Salmonella
Staph aureus
What does SAPHO and CRMO stand for?
Synovitis Acne Pustolosis Hyperostosis Osteitis (adults)
Chronic Recurrent Multifocal Osteomyelitis (kids)
What is Pott’s disease?
Vertebral TB
What is the classic triad of prosthetic joint infection?
- Severe skin infections
- Necrotizing pneumonia
- Invasive infections e.g. bacteraemia, septic arthritis
Antibiotic for open # prophylaxis?
IV co-amoxiclav
Which antibiotic is important in biofilm?
Rifampicin
Upper limb prosthesis infection bug?
Propionibacterium acnes
Antibiotic for septic arthritis <5 y?
Flucloxacillin + Ceftriaxone
Treatment of Clostridium tetani pyomyositis?
Surgical debridement + botulism antitoxin + penicillin/metronidazole + toxoid booster vaccination
Antibodies for Kawasaki?
Anti-endothelial
Funny rash + GI symptoms + renal failure = ?
Polyarteritis nodosa
Apple green birefringence with congo red staining = ?
Amyloid - found in multiple myeloma
Secondary malignancy in Paget’s?
Osteosarcoma
Mets of which cancer cause sclerosis (opacity) in bone?
Prostate
Kid born with tumour that looks like grapes coming out of the vagina = ?
Embryonal Rhabdomyosarcoma
List some side effects of methotrexate
Leukopeania, thrombocytopenia
Hepatitis/cirrhosis - lower alcohol consumption
Pneumonitis
Nausea
Teratogenic - males and females should stop 3 months before trying to conceive
Importance of Leflunomide?
V similar to methotrexate but longer half life
Either have to do a full washout or not get pregnant for 2 years after if you just stop it
Side effects of sulphasalazine?
Neutropenia Turns pee red Reversible infrtility in men Nausea Hepatitis SAFE IN PREGNANCY
Side effect of hydroxychloroquine?
When is this drug used?
Irreversible retinopathy
Used in palindromic RA
Side effects of gold?
Bone marrow suppression Glomerulonephritis Rash Mouth ulcers FBCs and proteinuria
Which is the only biologic you can use in connective tissue disease?
Rituximab
Treatment of ANCA associated vasculitis?
If organ involvement localized to resp or without organ threatening: MTX + steroids
If organ threatening: IV steroids + cyclophosphamide
