MSK

Question 1

What is the most commonly dislocated carpal bone; which nerve most likely to be affected?

Answer 1

Lunate; may compress median n.

Question 2

Which protein mediates Ca²⁺ activation of the contractile apparatus in cardiac and skeletal muscle?

Answer 2

Troponin (Tn)

Question 3

Why is cartilage, such as the hyaline cartilage in the knee joint particularly vulnerable to infection?

Answer 3

Cartilage is relatively avascular; immune system cannot access in an efficient fashion

Question 4

Most of the blood supply to the head of the femur arise from which artery?

Answer 4

Medial Circumflex Femoral a.

Question 5

Rheumatoid nodules will show what histologically?

Answer 5

Central areas of fibrinoid necrosis surrounded by palisading rim of epitheliod cells –> resembles granuloma

Question 6

Which virus has been implicated as a cause of Paget disease of bone?

Answer 6

Paramyxovirus (measeles and RSV) in osteoclasts of bone

Question 7

Axillary nerve runs closest to the humerus at which location?

Answer 7

Surgical neck

Question 8

Quadrangular space is formed by which structures?

Answer 8

• Teres minor
• Teres major
• Long head of triceps
• Surgical neck of humerus

Question 9

Which artery accompanies the axillary nerve in close proximity to the surgical neck of the humerus?

Answer 9

Posterior humeral circumflex a. (branch of axillary a.)

Question 10

Which nerve and roots innervate the serratus anterior m.?

Answer 10

Long thoracic n. (C5-C7)

Question 11

Which bands of skeletal muscle are delineated by the sarcomere, actin thin filaments and myosin thick filaments; how do they change during contraction?

Answer 11

• 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

Question 12

Which muscle is responsible for protrusion of the tongue and its innervation?

Answer 12

Genioglossus m. (CN XII)

Question 13

What is the only muscle of the tongue innervated by CN X and its function?

Answer 13

Palatoglossus ms. = pull tongue upward toward the palate

Question 14

Which 2 muscles of the hand have their origins on the hook of the hamate?

Answer 14

Flexor digiti minimi and opponens digiti minimi

Question 15

A sample of urine that turns black upon standing at room temperature is classically associated with what condition?

Answer 15

Onchronosis aka Alkaptonuria

Question 16

Alkaptonuria (ochronosis) is due to a deficiency of what; inherited how?

Answer 16

Deficiency of homogentisic acid oxidase –> Autosomal recessive

Question 17

What is the MOA of succinylcholine and what are 2 potentially life-threatening complications

Answer 17

• Binds and stimulates nAChR’s on skeletal muscle motor end plate –> Na+ and K+ out of cell = constant depolarization
• Hyperkalemia and malignant hyperthermia

Question 18

What is the effect of tensioning a skeletal muscle on both passive tension (preload) and maximal active tension?

Answer 18

• Preloading muscle ↑ passive tension
• Stretching skeletal muscle ↓ its ability to generate force = ↓ active tension

Question 19

Which vein drains lymph from the lateral side dorsum of foot and into which LN’s?

Answer 19

Short saphenous vein —> LN’s in popliteal fossa

Question 20

How can you calculate active tension of skeletal muscle generated using preload and total tension?

Answer 20

Active tension = Total tension - Passive tension

Question 21

Pain and tenderness at the anatomic snuffbox after a “FOOSH” injury is pathognomonic for what?

Answer 21

Scaphoid fracture (forms floor of snuffbox)

Question 22

Which 2 muscles and their associated CN are responsible for elevating the tongue?

Answer 22

• Styloglossus (CN XII)
• Palatoglossus (CN X)

Question 23

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?

Answer 23

• Radial nerve
• Inability to extend the wrist (wrist drop); trouble making tight fist
• Sensory loss of posterior forearm and hand

Question 24

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?

Answer 24

Right ventricle

Question 25

Osgood-Schlatter disease (OSD) is an overuse injury of the 2' ossification center (apophysis) located where and what is the involved ligament?

Answer 25

Pain/swelling at **tibial tubercle**, the insertion point of **_patellar ligament_**

Question 26

Osteocytes have long intracanalicular processes extending thru the ossified bone matrix which connect to osteocytes within neighboring lamellae via what?

Answer 26

**Gap junctions**

Question 27

During the skeletal muscle contraction cycle what is the result of ATP binding to myosin?

Answer 27

Causes **release** of the **myosin head** from its binding site on the **actin** **filament**

Question 28

How can you tell the difference btw a demyelinating neuropathy vs. axonal neuropathy using a nerve conduction study?

Answer 28

- **Demyelinating** due to damage of **myelin sheath** --\> _delayed_ (or blocked) nerve **conduction velocity** - **Axonal** due to damage of **nerve _axon_** --\> _reduced_ signal **amplitude**

Question 29

The common peroneal n. divides into a superficial and deep branch; what is each of these nerves responsible for?

Answer 29

- **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**

Question 30

A midshaft hemeral fracture should raise concern for deficits involving which nerve and artery?

Answer 30

- **Radial n.** - **Deep brachial a.**

Question 31

What should be included in the initial tx and work-up for Dermatomyositis?

Answer 31

- Initial tx is **systemic glucocorticoids** - Should evaluate for underlying occult **malignancy**: as is often part of a **paraneoplastic syndrome** (especially **adenocarcinoma**)

Question 32

What are the major differences between Type I and Type II muscle fibers?

Answer 32

- **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**

Question 33

The deep inguinal ring and superficial inguinal rings are physiologic openings in what?

Answer 33

- **Deep** ring is physiologic opening in the **transversalis fascia** - **Superficial** ring is physiologic opening in the **external oblique muscle aponeurosis**

Question 34

What is seen on biopsy which can differentiate Dermatomyositis from Polymyositis?

Answer 34

- **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\***