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    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Zygomaticus
    Muscle that raises the corners of the mouth.
    Ellipsoidal (Condyloid) Joints
    e.g., wrist
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.
    Inferior Nasal Conchae
    Bones inside the nasal cavity that filter and humidify air.
    Vomer Bone
    Bone forming the nasal septum.
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Iliolumbar Ligament
    Ligament connecting the ilium and lumbar vertebrae.
    Radius
    Forearm bone on the thumb side.
    Acromioclavicular Joint
    The acromioclavicular joint connects the clavicle and scapula at the top of the shoulder, enabling smooth scapular motion and stability during arm movements.
    Wormian Bones
    Sutural bones in the skull.
    Ulna
    Forearm bone on the pinky side.
    Buccinator
    Muscle that helps with chewing and blowing air out.
    Abductor Digiti Minimi Muscle
    The abductor digiti minimi muscle is a hypothenar muscle that abducts and flexes the little finger, aiding grip and precision in hand movements.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Quadriceps
    Rectus Femoris, Vastus Medialis, Vastus Lateralis, Vastus Intermedius.
    Sternum
    Breastbone located in the center of the chest.
    Acromioclavicular Ligament
    Ligament that connects the acromion to the clavicle.
    Coccygeus
    Pelvic floor muscle supporting the coccyx.
    Pubis
    Part of the pelvis that joins with the opposite side to form the pubic symphysis.
    Synchondroses
    Cartilaginous joints where bones are connected by hyaline cartilage.

    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? Sesamoid bones are bones that form within tendons, like the patella.