Biceps Brachii: Origin, Insertion & Function

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  • 0:00 The Two-Headed Gun
  • 1:26 General Muscle Functions
  • 2:32 Functions of the…
  • 3:30 Biceps vs Other Muscles
  • 4:37 Lesson Summary
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Lesson Transcript
Instructor: Catherine Konopka

Catherine has taught various college biology courses for 5 years at both 2-year and 4-year institutions. She has a Ph.D. in cell and molecular biology.

Did you know that the muscles in your upper arms not only bend your elbow, but also move your shoulder? In this lesson, you will learn about one of the major muscles of your arm, the biceps brachii.

The Two-Headed Gun

'Show me your guns!' and 'Welcome to the gun show!' mean very different things if you are at a gym versus at a shooting range. If you hear a person saying either of these in a fitness facility, they are referring to a muscle in your upper arm - the biceps brachii.

The biceps brachii, more commonly referred to as just biceps, is the most prominent muscle in the upper arm. The term brachii refers to the arm and is often put before terms relating to the arm. For instance, the brachial plexus are nerves extending into your arm, and the brachial artery is the major artery in your arm.

The biceps brachii has two heads, or origins, which is where the 'bi' in biceps comes from. Both heads originate on the scapula, which is the technical name for the shoulder blade. The long head attaches to the supraglenoid tubercle of the scapula, which is just above the space where the humerus, or upper arm, enters the shoulder. The short head attaches to the coracoid process of the scapula.

Both heads converge into one muscle, sometimes referred to as the 'belly,' that runs the length of the humerus. The biceps brachii crosses the inside of the elbow and attaches at the radial tuberosity, which is a feature on the radius - one of the two bones in- the lower arm.

General Muscle Functions

Before we get into the specifics of what the biceps brachii does, let's first review general principles of muscles. The only thing muscles can do is shorten and lengthen. That's it! Muscles are attached to bones, so when they shorten, they move bones. That doesn't sound like much, but when muscles shorten and lengthen in coordinated ways, all together they make the beautiful movements of the human body.

The bone on which a muscle originates remains stationary, while the bone on which the muscle attaches moves when the muscle shortens or contracts. Imagine a rubber band wrapped around a pole. The pole is like the stationary bone. If you pull on the rubber band with a finger, your finger is like the bone that can move. When the band (or muscle) shortens, your finger moves closer to the pole.

Muscles typically cross joints (places where two bones come together). When muscles shorten they bend or rotate that joint. Muscles can also stabilize a joint. In that case, the muscle prevents a bone from moving when gravity (or another force) is pulling at it.

Functions of the Biceps Brachii

The biceps brachii crosses two joints - the shoulder and the elbow - so it can influence movement of both joints. The biceps brachii can bring about a variety of movements when it shortens, including:

  • Supination: turning the palm upward. Let one arm hang with your palm facing behind you. When your biceps brachii contracts, it tugs on the radius and pulls it to the outside. This turns your palm to face forward.
  • Forearm flexion: bending the elbow with the palm facing forward. Let one arm hang with your palm facing forward. When your biceps brachii contracts, it will tug on your radius and pull it up, bending your elbow.

Because your biceps brachii also crosses the shoulder joint, it also helps with various movements of the shoulder, including:

  • Shoulder flexion: bringing the arm forward and upward
  • Horizontal adduction: bringing the arm across the body

Finally, the short head of the biceps brachii stabilizes your shoulder when you are carrying something heavy.

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