List the muscles that flex the elbow.
The correct answer and explanation is:
The primary muscles responsible for elbow flexion are:
- Biceps Brachii
- Brachialis
- Brachioradialis
1. Biceps Brachii
The biceps brachii is a two-headed muscle located on the front of the upper arm. It is one of the most well-known muscles involved in elbow flexion. The biceps brachii has two origins: one at the scapula (specifically, the supraglenoid tubercle) and the other at the coracoid process. Its insertion point is the radial tuberosity. When contracted, it flexes the elbow, bringing the forearm toward the upper arm. Additionally, it supinates the forearm (rotating it so the palm faces upward), contributing to elbow movement in specific postures or activities.
2. Brachialis
The brachialis is situated underneath the biceps brachii and is primarily responsible for flexing the elbow. Unlike the biceps brachii, the brachialis does not assist with supination or pronation of the forearm. It originates from the lower half of the anterior surface of the humerus and inserts into the ulnar tuberosity. Its role is to flex the elbow regardless of forearm position, making it particularly important for elbow flexion when the forearm is in a neutral or pronated position.
3. Brachioradialis
The brachioradialis is a muscle located in the forearm. It originates from the lateral supracondylar ridge of the humerus and inserts at the distal radius. The brachioradialis is unique because it is most active when the forearm is in a neutral position (thumb pointing upwards). It is a powerful flexor when the elbow is bent from an extended position, especially when resistance is applied.
These three muscles work together to flex the elbow joint, with each playing a slightly different role depending on the position of the forearm and the degree of flexion required. The biceps brachii is the primary muscle when the forearm is supinated, while the brachialis works consistently across all forearm positions. The brachioradialis adds strength when the forearm is in a neutral or pronated posture.