Video: Triceps brachii muscle

Hey everyone! This is Matt from Kenhub, and welcome to this quick video tutorial.

Today, I am going to talk with you about the triceps brachii muscle, specifically, its origin, insertion, and innervations.

The triceps brachii muscle is commonly referred to as the applause muscle in gyms all over, because if insufficiently toned, the back of the arm waggles when you clap your hands as it is located in the posterior aspect of the upper arm.

Now that you know its location, let’s discuss its composition. This three-headed muscle is composed of the long head, the medial head, and the lateral head. Note that two are named for their location: the medial and the lateral heads, and one for its size: the long head. That makes them relatively easy to identify.

Each one of these heads has a distinct origin, but they all combine distally into a thick tendon that connects it altogether to the joint and fascia in the elbow. The long head, which you see highlighted in green, originates in the infraglenoid tubercle of the scapula, on the lateral border of that bone. The medial head originates in the dorsal humerus, which is the long bone of the upper arm, distally from the radial sulcus. And the lateral head originates in the dorsal humerus proximally.

The long and lateral heads are easily palpated as they are more superficially located, but you can’t feel the medial head as it is tucked beneath them.

The three combine as they approach the elbow, and together, they form a thick tendon which inserts into the olecranon of the ulna and additionally to the capsule of the elbow joint and the antebrachial fascia.

The triceps brachii functions as a counterpart to the biceps brachii located on the anterior aspect of the upper arm. The triceps work to extend the arm, and the biceps are responsible for flexion. The triceps brachii also protect the capsule of the elbow joint during extreme extension.

The radial nerve serves as the supply for this muscle and is what causes the triceps brachii to extend the arm. The radial nerve runs from within the radial sulcus of the humerus, where it is covered by both the medial and lateral head and then courses down to the crook of the elbow where it rests between the biceps and triceps.