MSK Flashcards
What is the most commonly dislocated carpal bone; which nerve most likely to be affected?
Lunate; may compress median n.
Which protein mediates Ca2+ activation of the contractile apparatus in cardiac and skeletal muscle?
Troponin (Tn)
Why is cartilage, such as the hyaline cartilage in the knee joint particularly vulnerable to infection?
Cartilage is relatively avascular; immune system cannot access in an efficient fashion
Most of the blood supply to the head of the femur arise from which artery?
Medial Circumflex Femoral a.
Rheumatoid nodules will show what histologically?
Central areas of fibrinoid necrosis surrounded by palisading rim of epitheliod cells –> resembles granuloma
Which virus has been implicated as a cause of Paget disease of bone?
Paramyxovirus (measeles and RSV) in osteoclasts of bone
Axillary nerve runs closest to the humerus at which location?
Surgical neck
Quadrangular space is formed by which structures?
- Teres minor
- Teres major
- Long head of triceps
- Surgical neck of humerus
Which artery accompanies the axillary nerve in close proximity to the surgical neck of the humerus?
Posterior humeral circumflex a. (branch of axillary a.)
Which nerve and roots innervate the serratus anterior m.?
Long thoracic n. (C5-C7)
Which bands of skeletal muscle are delineated by the sarcomere, actin thin filaments and myosin thick filaments; how do they change during contraction?
- I-band contains a Z-disk, delineating a sarcomere and actin thin filaments; during contraction the I-band shortens
- A-band, delineated by ends of myosin thick filaments; does not change during contraction
Which muscle is responsible for protrusion of the tongue and its innervation?
Genioglossus m. (CN XII)
What is the only muscle of the tongue innervated by CN X and its function?
Palatoglossus ms. = pull tongue upward toward the palate
Which 2 muscles of the hand have their origins on the hook of the hamate?
Flexor digiti minimi and opponens digiti minimi
A sample of urine that turns black upon standing at room temperature is classically associated with what condition?
Onchronosis aka Alkaptonuria
Alkaptonuria (ochronosis) is due to a deficiency of what; inherited how?
Deficiency of homogentisic acid oxidase –> Autosomal recessive
What is the MOA of succinylcholine and what are 2 potentially life-threatening complications
- Binds and stimulates nAChR’s on skeletal muscle motor end plate –> Na+ and K+ out of cell = constant depolarization
- Hyperkalemia and malignant hyperthermia
What is the effect of tensioning a skeletal muscle on both passive tension (preload) and maximal active tension?
- Preloading muscle ↑ passive tension
- Stretching skeletal muscle ↓ its ability to generate force = ↓ active tension
Which vein drains lymph from the lateral side dorsum of foot and into which LN’s?
Short saphenous vein —> LN’s in popliteal fossa
How can you calculate active tension of skeletal muscle generated using preload and total tension?
Active tension = Total tension - Passive tension
Pain and tenderness at the anatomic snuffbox after a “FOOSH” injury is pathognomonic for what?
Scaphoid fracture (forms floor of snuffbox)
Which 2 muscles and their associated CN are responsible for elevating the tongue?
- Styloglossus (CN XII)
- Palatoglossus (CN X)
Which nerve is found in the musculospiral groove of the humerus and is commonly involved in fractures at this location; which signs/sx’s seen?
- Radial nerve
- Inability to extend the wrist (wrist drop); trouble making tight fist
- Sensory loss of posterior forearm and hand
Which structure is found extending from the right border of the sternum to approximately 2 inches to the left the sternum of the 3rd, 4th, and 5th ICS?
Right ventricle
Osgood-Schlatter disease (OSD) is an overuse injury of the 2’ ossification center (apophysis) located where and what is the involved ligament?
Pain/swelling at tibial tubercle, the insertion point of patellar ligament
Osteocytes have long intracanalicular processes extending thru the ossified bone matrix which connect to osteocytes within neighboring lamellae via what?
Gap junctions
During the skeletal muscle contraction cycle what is the result of ATP binding to myosin?
Causes release of the myosin head from its binding site on the actin filament
How can you tell the difference btw a demyelinating neuropathy vs. axonal neuropathy using a nerve conduction study?
- Demyelinating due to damage of myelin sheath –> delayed (or blocked) nerve conduction velocity
- Axonal due to damage of nerve axon –> reduced signal amplitude
The common peroneal n. divides into a superficial and deep branch; what is each of these nerves responsible for?
- Deep: innervates anterior compartment ms., which dorsiflex the foot and toes + sensation btw 1st and 2nd toe
- Superficial: innervates lateral compartment ms., which evert foot + sensation to dorsum of foot and lateral shin
A midshaft hemeral fracture should raise concern for deficits involving which nerve and artery?
- Radial n.
- Deep brachial a.
What should be included in the initial tx and work-up for Dermatomyositis?
- Initial tx is systemic glucocorticoids
- Should evaluate for underlying occult malignancy: as is often part of a paraneoplastic syndrome (especially adenocarcinoma)
What are the major differences between Type I and Type II muscle fibers?
- Type I = slow twitch; actions requiring low-level sustained force; aerobic metabolism; high myoglobin, are glycogen poor and contain many mitochondria
- Type II = fast twitch; rapid forceful pulses of movement; IIb derive ATP from anaerobic glycogenolysis and subsequent glycolysis and IIa generates ATP via aerobic metabolism
The deep inguinal ring and superficial inguinal rings are physiologic openings in what?
- Deep ring is physiologic opening in the transversalis fascia
- Superficial ring is physiologic opening in the external oblique muscle aponeurosis
What is seen on biopsy which can differentiate Dermatomyositis from Polymyositis?
- Dermatomyositis: shows perifascicular inflammation (around blood vessels) in a segmental pattern without vasculopathy
- Polymyositis: shows a patchy endomysial inflammation (direct invasion of individual muscle fibers) without prominent vascular involvement
*Both associated with anti-tRNA synthetase (anti-Jo-1) autoantibodies*
