Anatomy Flashcards
The extensor pollicis longus muscle is innervated by which of the following nerve?
A. Ulnar nerve
B. Median nerve
C. Anterior interosseous nerve
D. Musculocutaneous nerve
E. Posterior interosseous nerve
E. Posterior interosseous nerve
The extensor pollicis longus muscle attaches at the base of distal phalanx of the thumb and dorsal aspect of the ulna, providing thumb extension. It is innervated by the posterior interosseous nerve, a distal branch of the radial nerve originating from C7 and C8. The posterior interosseous nerve also supplies the all extensors of the forearm with the exception of the brachioradialis, extensor carpi radialis longus and anconeus. The median receives contributions from C5-T1 and provides innervation to the thumb flexors and the thenar muscles. The ulnar nerves is derived from C8-T1 and provides innervation to the adductor pollicis. The anterior interosseous nerve is a pure motor branch of the median nerve and supplies the flexor pollicis longus. The musculocutaneos nerve arises from C5-C7 and provides innervation for elbow flexion.
Injury to which of the following nerves is most likely to cause unilateral atrophy of the rhomboid muscle?
A. Spinal accessory nerve
B. Suprascapular nerve
C. Thoracodorsal nerve
D. Dorsal scapular nerve
E. Long thoracic nerve
D. Dorsal scapular nerve
The rhomboid muscles are an important stabilizer of the shoulder girdle and scapula. Functionally they elevate and rotate the scapula and injury is one cause of winged scapula. They consist of both the rhomboid major and minor and are innervated by the dorsal scapular nerve which arises from the C5 nerve root. The spinal accessory nerve (CN XI) supplies the trapezius and sternocleidomastoid muscles. The long thoracic nerve originates from C5, C6, and C7 providing innervation to the serratus anterior muscle which also stabilizes the scapula. The suprascapular nerve originates from the upper trunk innervating both the supra- and infraspinatus muscles which participate in shoulder abduction and external rotation. The thoracodorsal nerve is derived from C6, C7, and C8 branching from the posterior cord providing innervation to the latissimus dorsi muscle.
The extensor pollicis longus muscle is innervated by which of the following nerve?
A. Posterior interosseous nerve
B. Median nerve
C. Musculocutaneous nerve
D. Anterior interosseous nerve
E. Ulnar nerve
A. Posterior interosseous nerve
The extensor pollicis longus muscle attaches at the base of distal phalanx of the thumb and dorsal aspect of the ulna, providing thumb extension. It is innervated by the posterior interosseous nerve, a distal branch of the radial nerve originating from C7 and C8. The posterior interosseous nerve also supplies the all extensors of the forearm with the exception of the brachioradialis, extensor carpi radialis longus and anconeus. The median receives contributions from C5-T1 and provides innervation to the thumb flexors and the thenar muscles. The ulnar nerves is derived from C8-T1 and provides innervation to the adductor pollicis. The anterior interosseous nerve is a pure motor branch of the median nerve and supplies the flexor pollicis longus. The musculocutaneos nerve arises from C5-C7 and provides innervation for elbow flexion.
Froment sign is useful in the diagnosis of ulnar neuropathy. Weakness of which of the following muscles causes this sign to appear?
A. Flexor digiti minimi brevis
B. Flexor carpi ulnaris
C. Adductor pollicis
D. Extensor carpi ulnaris
E. Abductor digti minimi
C. Adductor pollicis
The ulnar nerve provides motor innervation to the hypothenar muscles (opens digiti minimi,
abductor digiti minimi, and flexor digit minimi brevis), the 3rd & 4th lumbricals, dorsal & palmar interossei, flexor carpi ulnaris, flexor digitorum profundus, palmaris brevis, and adductor pollicis. Weakness of the adductor pollicis results in compensation by the median innervated flexor pollicis longus to maintain thumb opposition/adduction. Froment’s sign is specific for ulnar neuropathy/injury evaluation.
The major output of the caudate/putamen is which of the following?
A. Globus pallidus
B. Substantia nigra
C. Ventrolateral thalamus
D. Cerebral cortex
E. Subthalamic nucleus
A. Globus pallidus
The major output of the caudate/putamen is the globus pallidus (both the external and internal portions).
Cells in the zona compacta of the substantia nigra (SNc) project to the putamen.
The SNc projection is excitatory to the direct pathway. In the direct pathway, the putamen inhibits the inhibitory output of the globus pallidus interna (GPi) leading to increased excitatory output of the ventrolateral (VL) thalamus to the cerebral cortex. Excitation of the direct pathway by the SNc leads to facilitation of movement.
The SNc projection is inhibitory to the indirect pathway. In the indirect pathway, the putamen inhibits the inhibitory output of the globus pallidus externa leading to increased excitatory output of the subthalamic nucleus (STN). The STN excites the GPi to inhibit the VL thalamus and, therefore, provide less excitation of the cerebral cortex. Excitation of the indirect pathway leads to inhibition of movement. Inhibition of the indirect pathway by the SNc leads to facilitation of movement.
The above is well illustrated in Figure 1 of
Bergman H, Wichmann T, DeLong MR. Reversal of experimental parkinsonism by lesions of the subthalamic nucleus. Science. 1990;249(4975):1436-8. https://pubmed.ncbi.nlm.nih.gov/2402638/
The external capsule is located between which of the following?
A. Lentiform nucleus and caudate
B. Claustrum and insular cortex
C. Putamen and claustrum
D. Lentiform nucleus and thalamus
E. Caudate and thalamus
C. Putamen and claustrum
The external capsule is located between the putamen and claustrum, and between the claustrum and insular cortex. It contains mainly corticocortical association fibers, including the inferior fronto- occipital fasciculus and the uncinate fasciculus. The internal capsule is located between the lentiform nucleus and caudate, lentiform nucleus and thalamus, and caudate and thalamus.
Paralysis of the coracobrachialis muscle occurs after injury to which of the following nerves?
A. Musculocutaneous nerve
B. Thoracodorsal nerve
C. Dorsal scapular nerve
D. Axillary nerve
E. Ulnar nerve
A. Musculocutaneous nerve
The coracobrachialis arises from the coracoid process and inserts on the upper humerus. It is innervated by the musculocutaneous nerve and can a wide variation in size. It acts to flex and adduct the arm, centered at the shoulder or glenohumeral joint. Isolated injury or paralysis in the absence of biceps/brachialis injury is rare. The ulnar nerve originates from C8 and T1 and notably intervates the intrinsic muscles of the hand. The thoracodorsal nerve is derived from C6-C8 and supplies the latissimus dorsi muscle. The dorsal scapular nerve arises from C5 and provides innervation to the rhomboids. The axillary nerve is composed of fibers from C5 and C6 and provides inneration to the deltoid and teres minor.
The basal ganglia project directly to which of the following?
A. Cerebral cortex
B. Amygdala
C. Hippocampus
D. Substantia nigra
E. Thalamus
E. Thalamus
Although the effect of the basal ganglia circuitry is upon the cerebral cortex, the direct projection is to the thalamus, especially the ventrolateral (VL) portion. The substantia nigra provides input to the basal ganglia rather than the converse. The basal ganglia do not project to the amygdala or hippocampus.
In a patient who underwent a biopsy of the sural nerve, which of the following neurological deficits is most likely?
A. Dorsiflexion weakness
B. Foot inversion weakness
C. Lateral malleolus numbness
D. Foot eversion weakness
E. Medial malleolus numbness
C. Lateral malleolus numbness
The sural nerve is a pure sensory nerve that arises the sciatic nerve and more distally from the tibal and common peroneal nerves at the level of popliteal fossa. It provides sensory innervation to the lateral foot and ankle. Post-biopsy, injury, or graft harvest deficits typically leave patients with sensory deficits on the postero-lateral aspect of the foot. Foot eversion and dorsiflexion are provided by the peroneal nerve a terminal branch of the sciatic nerve. Inversion is provided by the tibial nerve the other terminal branch of the sciatic nerve.
