Anterior Upper Extremity Muscles: Origins, Insertions, and Actions

Anterior Upper Extremity Muscles

Overview

The anterior muscles of the upper extremity are essential for movements of the shoulder, arm, and forearm. Understanding their origins, insertions, and actions is fundamental for comprehending upper limb function and for clinical applications such as injury assessment and rehabilitation.

Deltoid

• Origin: Clavicle and acromion process of the scapula

• Insertion: Diaphysis of the humerus (specifically, the deltoid tuberosity)

• Action: Arm abduction (raises the arm away from the body)

• Example: Lifting the arm to the side during a jumping jack exercise.

Biceps Brachii

• Origin: Coracoid process of the scapula (short head; the long head originates from the supraglenoid tubercle)

• Insertion: Radial tuberosity of the radius

• Action: Elbow flexion (bends the forearm at the elbow) and supination of the forearm

• Example: Flexing the elbow to lift a weight during a biceps curl.

• Additional info: The biceps brachii also assists in supinating the forearm (turning the palm upward).

Brachialis

• Origin: Distal humerus

• Insertion: Coronoid process of the ulna

• Action: Elbow flexion (lifts the ulna as the elbow is flexed)

• Example: Contributes to elbow flexion regardless of forearm position (pronated or supinated).

• Additional info: The brachialis is considered the primary flexor of the elbow because it acts directly on the ulna.

Brachioradialis

• Origin: Distal humerus (lateral supracondylar ridge)

• Insertion: Styloid process of the radius

• Action: Elbow flexion (lifts the radius during flexion, especially when the forearm is in a mid-pronated position)

• Example: Flexing the elbow when lifting a glass to the mouth, especially with the thumb pointing upward.

• Additional info: The brachioradialis is most active when the forearm is in a neutral position (thumb up), such as during a hammer curl.

Summary Table: Anterior Upper Extremity Muscles

Muscle	Origin	Insertion	Action
Deltoid	Clavicle, acromion process	Diaphysis of humerus (deltoid tuberosity)	Arm abduction
Biceps Brachii	Coracoid process (short head)	Radial tuberosity	Elbow flexion, forearm supination
Brachialis	Distal humerus	Coronoid process of ulna	Elbow flexion (lifts ulna)
Brachioradialis	Distal humerus	Styloid process of radius	Elbow flexion (lifts radius)