Triceps Brachii

1. Overview

The triceps brachii is a large, three-headed skeletal muscle located on the posterior aspect of the upper arm. As the primary extensor of the elbow joint, it plays a crucial role in straightening the forearm. The triceps is also important for shoulder joint stability and movement. Its powerful action is essential in pushing, throwing, and weight-bearing activities.

2. Location

The triceps brachii occupies the posterior compartment of the arm:

• Proximally: Originates from both the scapula and the humerus.

• Distally: Inserts on the olecranon process of the ulna.

• Superficial to: The humerus and deep fascia of the upper arm.

• Adjacent to: Biceps brachii (anteriorly) and deltoid (superiorly).

3. Structure

The triceps brachii has three distinct heads:

• Long head: Originates from the infraglenoid tubercle of the scapula.

• Lateral head: Originates from the posterior surface of the humerus, superior to the radial groove.

• Medial head: Originates from the posterior surface of the humerus, inferior to the radial groove.

All three heads converge into a common tendon that inserts on the olecranon process of the ulna.

• Innervation: Radial nerve (C6–C8).

• Blood supply: Deep brachial artery (profunda brachii) and collateral branches of the brachial artery.

4. Function

The triceps brachii has two main actions:

• Elbow extension: All three heads extend the forearm at the elbow joint.

• Shoulder extension and adduction: The long head also assists in extension and adduction of the arm at the shoulder joint.

These actions are essential in movements such as pushing open a door, rising from a chair, or performing a push-up.

5. Physiological role(s)

The triceps brachii contributes to several important physiological functions:

• Upper limb mobility: Allows full range of elbow motion in combination with the biceps brachii.

• Postural support: Assists in maintaining arm and shoulder posture during load-bearing tasks.

• Force generation: As a powerful muscle, it generates the force required for explosive movements like throwing or punching.

• Joint stability: Helps stabilize the shoulder joint, particularly when the arm is adducted or extended behind the body.

6. Clinical Significance

The triceps brachii can be affected by various injuries and conditions:

• Triceps strain or tear:

  • Results from sudden or excessive loading, often seen in athletes performing overhead or pushing motions.

• Radial nerve palsy:

  • Injury to the radial nerve may weaken or paralyze the triceps, leading to difficulty in elbow extension and “wrist drop.”

• Tendonitis:

  • Repetitive strain can lead to inflammation of the triceps tendon, especially near the olecranon.

• Triceps reflex testing:

  • Used clinically to assess the integrity of the C7 and C8 spinal cord segments and radial nerve function.

• Rehabilitation importance:

  • Commonly targeted in strengthening programs for upper limb recovery, especially after injury or surgery.