MSK/Skin Physiology and Anatomy

Question 1

Desmosome (macula adherens)

Answer 1

Provides structural support via keratin interactions between adjacent cells.

Autoantibodies vs. desmosomes –> pemphigus vulgaris

Question 2

Hemidesmosome

Answer 2

Connects keratin in basal cells to underlying basement membrane.

Autoantibodies vs. hemidesmosome –> bullous pemphigoid (“hemidesmosomes are bullow”)

Question 3

Wrist bones

Answer 3

Radius-ulna (1st row): Scaphoid, Lunate, Triquetrum, Pisiform (“So Long to Pinky”)

Ulna to radius (2nd row): Hamate, Capitate, Trapezoid, Trapezium (“Here Comes The Thumb”)

Question 4

Dislocation of the lunate bone

Answer 4

May cause carpal tunnel syndrome

Question 5

Damage to hook of hamate (FOOSH)

Answer 5

May cause ulnar nerve injury

Question 6

Axillary nerve (C5-C6)

Answer 6

Innervates deltoid, teres minor, and long head of triceps brachii.

Receives sensory info from shoulder joint and and lateral arm.

Damaged by fractured surgical neck of humerus and anterior dislocation of humerus (deltaoid paralysis)

Question 7

Musculocutaneous (C5-C7)

Answer 7

Innervates corachobrachialis, biceps brachii, and greater part of brachialis.

Damaged by upper trunk compression (difficulty flexing elbow)

Question 8

Radial (C5-T1)

Answer 8

Innervates posterior compartment of arm and forearm (triceps and brachialis)

Damaged by midshaft fracture of humerus or compresion of axilla (wrist drop, decreased grip strength, loss of sensation over posterior arm/forearm and dorsal hand)

Question 9

Median (C5-T1)

Answer 9

Innervates all the flexors in the forearm except flexor carpi ulnaris and flexor digitorum profundus (ulnar nerve)

Damaged by supracondylar fracture of humerus, carpal tunnel syndrome, and wrist laceration (“Pope blessing”, loss of sensation over thenar eminence and dorsal/palmar aspects of latearl 3.5 fingers with proximal lesion)

Question 10

Ulnar (C8-T1)

Answer 10

Damaged by fracture of medial epicondyle of humerus or hook of hamate (“Ulnar claw”; radial deviation of wrist with flexion; loss of abduction/adduction of fingers; loss of sensation over medial 1/5 fingers)

Question 11

Recurrent branch of median nerve (C5-T1)

Answer 11

Damaged by superficial laceration of palm (“ape hand deformity”, loss of thenar muscle group; no loss of sensation)

Question 12

Erb palsy (“waiter’s tip”)

Answer 12

Tear of upper trunk (C5-C6) due to lateral traction on neck during delivery (infants) or trauma

Results in adduction (deltoid, supraspinatus), internal rotation (infraspinatus), and extension with pronation (biceps brachii)

Question 13

Kulmpke palsy

Answer 13

Tear of lower trunk (C8-T1) due to upward force on arm during delivery (infants) or trauma

Results in total claw hand (intrinsic hand muscles)

Question 14

Thoracic outlet syndrome

Answer 14

Compression of lower trunk and subclavian vessels due to cervical rib injury or Pancoast tumor.

Results same as Klumpke palsy (total claw hand)

Question 15

Winged scapula

Answer 15

Lesion of long thoracic nerve (C5-C7) due to axillary node dissection s/p mastectomy or stab wounds

Cannot abduct arm above horizontal position (serratus anterior)

Question 16

Lesion to obturator nerve (L2-L4)

Answer 16

Decreased adduction and decreased sensation of medial thigh

Question 17

Lesion to femoral nerve (L2-L4)

Answer 17

Decreased thigh flexion and leg extension

Question 18

Lesion to common peroneal nerve (L4-S2) due to trauma or compression of lateral leg

Answer 18

Foot drop, “steppage gait”, and loss of sensation on dorsum of foot.

“PED” = Peroneal Everts and Dorsiflexes; if injured foot dropPED

Sciatic nerve (L4-S3) - splits into common peroneal and tibial nerves

Question 19

Lesion to tibial nerve (L4-S3) due to knee trauma or Baker cyst

Answer 19

Inability to curl toes and loss of sensation on sole of foot

“TIP” = Tibial Inverts and Plantarflexes; if injured, can’t stand on TIPtoes

Sciatic nerve (L4-S3) - splits into common peroneal and tibial nerves

Question 20

Lesion to superior gluteal nerve (L4-S1) due to polio or posterior hip dislocation

Answer 20

Trendelenburg sign/gait due to weakness gluteal medius and minimus. Lesion is contralateral to dropped hip.

Question 21

Lesion to inferior gluteal nerve (L5-S2) due to posterior hip dislocation

Answer 21

Difficulty climbing stairs and rising from seated position due to weakness to gluteal maximius

Question 22

Radial head subluxation (nursemaid’s elbow)

Answer 22

Caused by tear of annular ligament from its periosteal attachment at the radial neck

Child presents with adducted arm with extended elbow and pronated forearm. Any motion of the elbow produces pain.