Biceps Brachii

Origin, Insertion, Nerve Supply

Feature	Detail
Long head	Supraglenoid tubercle + glenoidal labrum; tendon intracapsular
Short head	Tip of coracoid process (with coracobrachialis)
Insertion	Posterior rough part of radial tuberosity + bicipital aponeurosis
Nerve supply	Musculocutaneous nerve (C5, C6)

Flat fibrous expansion → passes medially across cubital fossa → blends with deep fascia of forearm
Separates median cubital vein (superficial) from brachial artery + median nerve (deep) → protects structures during venepuncture

Flexor of elbow — most powerful in supination
Supinator of forearm — most powerful supinator, especially with elbow flexed
Weak shoulder flexor; long head stabilises humeral head in glenoid

Rupture of long head tendon — friction in bicipital groove or forceful contraction; detached belly retracts → “Popeye” deformity (bulge in lower arm); common >35 yrs
Erb’s palsy (C5, C6) — loss of elbow flexion + forearm supination → “waiter’s tip” posture

Biceps brachii is a fusiform muscle of the anterior compartment of the arm with two heads of origin.

Feature	Detail
Long head	Supraglenoid tubercle of the scapula and the glenoidal labrum; the tendon is intracapsular (within the shoulder joint capsule)
Short head	Tip of the coracoid process of the scapula (along with coracobrachialis)
Insertion	Posterior rough part of the radial tuberosity (a bursa separates the tendon from the anterior part of the tuberosity); also gives off the bicipital aponeurosis
Nerve supply	Musculocutaneous nerve (C5, C6)

A flat fibrous expansion from the biceps tendon that passes medially across the cubital fossa to blend with the deep fascia of the forearm (attaching to the subcutaneous border of the ulna).
Clinically important: it separates the median cubital vein (superficial) from the brachial artery and median nerve (deep), protecting these structures during venepuncture at the cubital fossa.

Flexor of the elbow joint — particularly powerful when the forearm is supinated.
Supinator of the forearm — the most powerful supinator, especially when the elbow is flexed (the “screwdriver” action — tightening a screw with the right hand involves simultaneous elbow flexion and forearm supination by biceps).
Acts as a weak flexor of the shoulder joint (long head also helps stabilize the head of the humerus in the glenoid cavity).

Rupture of the long head tendon: May occur due to repetitive friction of the tendon in the bicipital groove, or from sudden forceful contraction (e.g., during weight lifting), typically in individuals over 35 years. The detached muscle belly retracts distally, producing the characteristic “Popeye” deformity — a bulge in the lower arm.
Erb’s palsy (C5, C6 root injury): Paralysis of biceps brachii contributes to extension at the elbow (loss of flexion) and pronation of the forearm (loss of supination), forming part of the classical “waiter’s tip” posture.

Diagram content will be added later.