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    From Musculoskeletal System

    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Phalanges (14 bones)
    14 bones forming the toes.
    Medial Collateral Ligament (MCL)
    Knee ligament that stabilizes the inner knee.
    Tibia
    Shin bone, the larger bone in the lower leg.
    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Sartorius
    Longest muscle in the body responsible for hip flexion.
    Sutures (in the skull)
    Fibrous joints between skull bones.
    Sacroiliac Ligaments
    Ligaments connecting the sacrum to the iliac bones.
    Synchondroses
    Cartilaginous joints where bones are connected by hyaline cartilage.
    Syndesmoses
    Fibrous joints where bones are connected by ligaments.
    Carpals (8 bones)
    8 wrist bones.
    Posterior Longitudinal Ligament
    Spinal ligament running along the back of the vertebral column.
    Obliques (External and Internal)
    Muscles responsible for torso rotation.
    Temporalis
    Muscle involved in closing the jaw.
    Coracoacromial Ligament
    Ligament that connects the acromion to the coracoid process.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Rotator Cuff Muscles
    Supraspinatus, Infraspinatus, Teres Minor, Subscapularis.
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Acromioclavicular Ligament
    Ligament that connects the acromion to the clavicle.
    Patella
    Knee cap, protecting the knee joint.
    Coccyx
    Tailbone, the remnant of the tail in humans.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Ilium
    Uppermost and largest part of the hip bone.
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.

    Biceps Brachii

    Reviewed by our medical team

    Muscle responsible for elbow flexion.

    1. Overview

    The biceps brachii is a prominent, two-headed muscle located in the anterior compartment of the upper arm. It is primarily responsible for forearm flexion and supination, playing a key role in elbow and shoulder movements. The term “biceps” means “two heads,” referring to its dual origin from the scapula. Due to its visibility and size, the biceps is commonly associated with strength and is a key muscle in both athletic performance and clinical rehabilitation.

    2. Location

    The biceps brachii is situated in the anterior upper arm, between the shoulder and the elbow:

    • Proximal attachment:

      • Long head: Supraglenoid tubercle of the scapula (via the intertubercular groove).

      • Short head: Coracoid process of the scapula.

    • Distal attachment: Radial tuberosity of the radius and bicipital aponeurosis into the deep fascia of the forearm.

    It lies superficial to the brachialis muscle and is covered by skin and fascia in the upper arm.

    3. Structure

    The biceps brachii has two heads and a shared distal tendon:

    • Long head: Travels through the shoulder joint and the intertubercular groove of the humerus; more lateral.

    • Short head: Lies medially and shares a common origin with the coracobrachialis.

    • Muscle belly: The two heads converge into a single, thick, fusiform muscle belly.

    • Distal tendon: Inserts on the radial tuberosity and gives off a flat sheet—the bicipital aponeurosis—to blend with forearm fascia.

    The biceps is innervated by the musculocutaneous nerve (C5–C7) and receives its blood supply from the brachial artery.

    4. Function

    The biceps brachii has both primary and secondary functions involving the forearm and shoulder:

    • Forearm supination: Most powerful supinator of the forearm when the elbow is flexed.

    • Elbow flexion: Assists in flexing the forearm, especially during supinated movements (e.g., lifting a dumbbell).

    • Shoulder flexion: Both heads help in raising the arm at the shoulder joint.

    • Shoulder stabilization: Long head helps stabilize the humeral head within the glenoid cavity during arm motion.

    5. Physiological role(s)

    Beyond movement, the biceps brachii contributes to several physiological roles:

    • Functional strength: Used extensively in lifting, pulling, and carrying tasks.

    • Muscle tone and contour: Plays a cosmetic role in upper arm appearance; often targeted in strength training.

    • Reflex testing: The biceps reflex (C5) is a clinical tool for evaluating the integrity of the musculocutaneous nerve and spinal segment function.

    • Joint protection: Helps protect the elbow joint by dynamically supporting forearm movement under load.

    6. Clinical Significance

    The biceps brachii is involved in various injuries and clinical conditions:

    • Biceps tendinitis:

      • Inflammation of the long head tendon, often from overuse or repetitive overhead activity (e.g., in swimmers or throwers).

    • Biceps tendon rupture:

      • Typically involves the long head; may cause a visible bulge (“Popeye deformity”) and weakness in supination and flexion.

    • Bicipital groove instability:

      • The long head tendon can sublux or dislocate from the intertubercular groove, causing clicking and pain.

    • Musculocutaneous nerve injury:

      • May result in weakened flexion/supination and sensory deficits in the lateral forearm.

    • Biceps reflex testing:

      • Used in neurological exams to assess C5 spinal cord function. Absence may indicate upper motor neuron lesions or peripheral nerve damage.

    • Overuse syndromes:

      • Common in athletes and manual laborers; can lead to chronic strain and functional limitation if not addressed early.

    Did you know? Tendons attach muscles to bones.