Muscles innervated by radial nerve

Question

Which of the following muscles is innervated by the radial nerve?

1. A) Flexor carpi ulnaris
2. B) Triceps brachii
3. C) Palmaris longus
4. D) Pronator teres

Answer 1

B) Triceps brachii

1. Explanation: The radial nerve pierces the triceps muscle group, in between the long and middle heads. While traversing through, it innervates the triceps brachii. The radial nerve stems from nerve roots C5-T1, and the triceps muscle is innervated by roots C6-C8.

A) The flexor carpi ulnaris is innervated by the ulnar nerve.

C) The palmaris longus is innervated by the median nerve.

D) The pronator teres is also innervated by the median nerve.

Answer 2

Answer: (B) Triceps Brachii muscle is innervated by the Radial nerve. 

Rationales for Correct Answer (B): 

Radial Nerve

Spinal Roots: C5-T1.

Motor Function: The radial nerve primarily innervates muscles in the posterior compartment of the arm and forearm, responsible for extension of the elbow, wrist, and fingers.

Reflex Involvement: The triceps reflex (elbow extension) tests the radial nerve and spinal roots C6-C8.

Triceps Brachii Muscle

Innervation: Radial nerve (C6-C8).

Motor Function: Extends the forearm at the elbow and assists in shoulder extension.

Rationale: This muscle is in the posterior compartment of the arm, which is innervated by the radial nerve. The triceps reflex also tests the integrity of the radial nerve and spinal roots C6-C8.

Rationales for Incorrect Answers (A, C, D):

A) Flexor carpi ulnaris

1. Innervation: Ulnar nerve (C8-T1), not the radial nerve.
2. Motor Function: Flexes and adducts the wrist.
3. Rationale: This muscle is part of the anterior compartment of the forearm, which is innervated by the median or ulnar nerves, not the radial nerve.

C) Palmaris longus

1. Innervation: Median nerve (C7-C8).
2. Motor Function: Weak flexion of the wrist; not consistently present in all individuals.
3. Rationale: Part of the anterior compartment of the forearm, this muscle is innervated by the median nerve, not the radial nerve.

D) Pronator teres

1. Innervation: Median nerve (C6-C7).
2. Motor Function: Pronates the forearm and assists in elbow flexion.
3. Rationale: Part of the anterior compartment of the forearm, this muscle is innervated by the median nerve, not the radial nerve.

 

Answer 3

Answer: B) Triceps brachii

1. Explanation: The radial nerve innervates the triceps brachii, which is involved in elbow extension. The flexor carpi ulnaris, palmaris longus, and pronator teres are innervated by the median or ulnar nerves.