Biceps brachii

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ΕΤΥΜΟΛΟΓΙΑ

Latin, biceps two-headed, brachii of the arm
This page refers to biceps brachii in the upper arm. For the muscle in the leg, see biceps femoris.

Biceps brachii (commonly 'biceps') is a large, two-headed muscle of the upper arm. It is notable for the fact that it affects three (or strictly four) joints.

Biceps brachii
Biceps brachii.GIF
System: Muscle
Function: Elbow flexion, forearm supination
Origin: Long head: supraglenoid tubercle of the scapula
Short head: coracoid process of the scapula
Branches:
Insertion: Radial tuberosity
Arterial supply: Brachial artery
Venous drainage:
Lymphatic drainage:
Innervation: Musculocutaneous nerve (C5 - C7)
Vertebral levels:
Search for Biceps brachii in Gray's.


Contents

Surface Anatomy

Biceps is clearly palpable on the anterior surface of the upper arm, where it forms much of the muscle bulk.

Shape

Biceps originates from two heads - the long head and the short head. The two heads unite a short distance above the elbow, ending as a broad, flattened tendon. The tendon gives off the bicipital aponeurosis before twisting on itself so that the anterior portion faces laterally, and inserting onto the posterior part of the radial tuberosity. A bursa separates the tendon and the anterior part of the tuberosity.

Long head

Arises from the supraglenoid tuberosity at the upper margin of the glenoid fossa, being continuous with the glenoid labrum. It passes through the joint cavity of the shoulder, enclosed in a sheath of synovial membrane, arching around the head of the humerus. It emerges from the capule inferiorly, travelling through the intertubercular groove beneath the transverse humeral ligament and tendon of pectoralis major. The tendon becomes surrounded by muscle within the groove, this muscle bulk growing larger as it descends distally and then receeding before it joins with the short head.

Short head

Arises by a flat tendon from the tip of the coracoid process in common with the tendon of coracobrachialis. The tendon becomes surrounded by muscle shortly after leaving the origin, this muscle bulk growing larger as it descends distally and then receeding before it joins with the long head.

Actions

Joints Affected

Origin

Long head:

  • Supraglenoid tubercle of the scapula, as a continuation of the glenoid labrum

Short head:

Insertion

Nerve Supply

Relations

Posteriorly:

The long head travels through the shoulder joint capsule, adjacent to the head of humerus

Clinical Relevance

  • May rupture. This is usually the long head in older adults [1]. The muscle still contracts and the appearance has been described as a "Popeye Muscle" from the cartoon character.[2] Surgical repair of the long head is seldom beneficial. Rupture of the insertion requires surgery[3].

Variations

  • 10% show a third head which is continuous with the upper fibres of brachialis, lying posterior to the brachial artery and inserting into the bicipital aponeurosis and tendon
  • In a small amount of cases this third head itself has two parts, one anterior and one posterior to the brachial artery
  • Rarely a fourth head arises from the intertubercular groove or the greater tubercle
  • Rarely other arrangements or origins of heads may occur
  • A slip of muscle may pass from the posterior portion of the muscle over the brachial artery to the medial intermuscular septum or medial epicondyle, or rarely to pronator teres or brachialis
  • The long head may be absent
  • The long head may arise from the intertubercular groove

References