Triceps (medial head) !
The medial head of the triceps is the deep part of the triceps, mostly hidden by the other two heads; it straightens the elbow in every position.
Official name: Triceps brachii, medial head
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What it is
The deep head of the triceps, against the humerus.
What it does
Straightens the elbow in every position.
Key facts
- Origin
- Posterior humerus below the radial groove; lower medial and lateral intermuscular septa
- Insertion
- Olecranon
- Action
- Extends the elbow
- Nerve
- Radial nerve (C6–C8)
- Blood supply
- Deep brachial artery
Relations
- Superficial
- Triceps (long head) and triceps (lateral head)
- Deep
- Back of the humerus below the radial groove; near the elbow, the olecranon fossa and posterior elbow capsule, to which deep fibres attach
- Medial
- Ulnar nerve and the superior ulnar collateral artery, behind the medial intermuscular septum
- Above
- Radial nerve and deep brachial artery in the radial groove
How to find it
Felt just above the elbow on either side of the triceps tendon, especially medially, as the elbow is straightened against resistance from a bent position.
Examination
- Palpation behind the medial epicondyle while the elbow bends: a second snap after the ulnar nerve's points to a snapping medial head of triceps; the nerve alone gives one
On imaging
Deep to the long and lateral heads; on axial MRI it wraps the back of the distal humerus, with the ulnar nerve on its medial side. Distal triceps tendon tears are uncommon; the lateral radiograph may show a small flake of bone pulled off the olecranon (flake sign), and ultrasound or MRI show the tendon gap.
Clinical notes
- Snapping triceps: part of the medial head slips over the medial epicondyle on flexion, often with the ulnar nerve, and can be mistaken for ulnar nerve subluxation
- Deep fibres pull the posterior capsule away so it is not pinched in extension
- Approaches that split this head near the elbow can cut the nerve to the anconeus
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
Where does the medial head of triceps arise, and how is it covered?
From the posterior humerus below the radial groove; the long and lateral heads cover it except just above the elbow.
What is a snapping triceps, and what is it mistaken for?
Part of the medial head slips over the medial epicondyle on flexion; it is mistaken for ulnar nerve subluxation.
Which nerve runs down the medial surface of the medial head of triceps?
The ulnar nerve, behind the medial intermuscular septum, with the superior ulnar collateral artery.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- caput mediale musculi tricipitis brachii TA2 2474
- Official Spanish (DeCS)
- Cabeza medial del músculo tríceps braquial
- English (TA2)
- Triceps brachii, medial head
- Also called
- deep head of triceps
Related
Sources: Terminologia Anatomica (TA2); Anatomy, Shoulder and Upper Limb, Triceps Muscle.
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Representative model, for educational purposes only.
