Anterior (Front) Arm
Bi-ceps ( "Bi"=two ; "cep"=head ) brachii ( "brachii"=Brachium, the anatomical term for the "upper arm" ).
All together: The Biceps brachii is the 2-Headed Muscle in the Upper Arm.
Short Head: Coracoid Process of the scapula.
Essentially, the insertion is deep inside your armpit, towards the front/top.
Long Head: Supraglenoid Tubercle of the scapula.
Essentially, the tendon of the long head of the Biceps brachii climbs up the outer side of your arm, and wraps around the top of your shoulder. Its attachment is just on top of the joint cavity. The tendon itself passes through a groove in the humerus bone, called the intertubercular sulcus. This groove helps keep the tendon on track, and is kept lubricated by a structure called a Tendon Sheath.
Both heads merge together to form 1 common tendon on the other end, which inserts distally, into the forearm. There are 2 points of attachment for the Biceps brachii tendon: the primary attachment into the radius, close to the elbow; AND via a small sheet-like tendon, called an aponeurosis, into the fascia of the forearm. (Fascia is a type of connective tissue that surrounds muscles and helps give them structure, and is often the target of massages and foam rolling. Post about fascia TBA)
There are 2 bones in the forearm, the radius and the ulna. The radius is moved when you flex your arm because the Biceps brachii inserts onto it. To move the ulna, so that the entire forearm flexes, you would also want to contract the Brachialis muscle. (Most people contract both simultaneously, and would have a difficult time doing otherwise)
- The primary action of the Biceps brachii is to bend the Elbow Joint. The anatomical term for this is Flexion of the elbow, or Flexion of the Forearm AT the Elbow. Although most people do so casually, it is technically incorrect to say that the Biceps brachii flexes the arm when talking about this specific movement (although as we are about to see, flexion of the arm IS one of it's secondary actions).
- Flexion of the Arm (Humerus bone) at the Shoulder Joint. This is like when you raise your arm straight out in front of you. The primary muscles for this movement are the Deltoids (anterior belly) and the Pectoralis major (clavicular head), but the Biceps brachii helps out a little bit. This is why you feel a little tension/soreness in your arms when you are doing Front Shoulder Raises for your shoulder day workouts.
- When a muscle acts as antagonist, it is trying to resist the action of a different muscle. For example, the Triceps brachii sits on the back of the arm, and straightens (extends) the elbow. The Biceps brachii is the antagonist of the Triceps because the Biceps brachii flexes the elbow, and vice versa (the Triceps is the antagonist of the Biceps. They have opposite functions)
The Biceps brachii is innervated by the Musculocutaneous nerve. This nerve also innervates the Brachialis and Coracobrachialis muscles. Damage to this nerve (such as pinching) would result in poor ability to flex the elbow or tingling in the upper arm.
This nerve comes from the Lateral Cord of the Brachial Plexus. The Brachial Plexus is the main set of nerves that innervate different parts of the arm, forearm, shoulder, back and chest. Depending on what nerves or parts of the Brachial Plexus may be pinched, you could have different combinations of muscles working improperly.
The Biceps brachii is supplied by the Brachial Artery. This is the main artery that comes into the arm from the shoulder region (shoulder region is called the Axilla).
Blood Flow: Heart -> Aorta -> -Brachiocephalic Trunk -> Subclavian Artery -> Axillary Artery -> Brachial Artery -> Biceps brachii
You can actually feel your heartbeat in your arm by feeling the brachial artery, especially during workouts when your pulse is stronger. You just have to lightly press along the inside of your arm, close to the armpit.