Posterior Arm & Elbow

Where is the Triceps brachii muscle?

On the *back of the upper arm*, with three heads — long (from scapula), lateral & medial (from humerus). It forms most of the posterior arm bulk. 💪 Mnemonic: "Tri = three heads, one mission."

What is the function of Triceps brachii?

It's the *main elbow extensor and stabilizes the shoulder joint via its long head. Supplied by Radial nerve (C6-C8)*. ⚡

Where does the long head of Triceps attach?

From the *infraglenoid tubercle of scapula → joins lateral & medial heads → inserts on olecranon* of ulna.

Where is the Anconeus muscle?

Small triangular muscle near the *posterior elbow*, between lateral epicondyle and olecranon. It helps extend the elbow. 📍 Mnemonic: "Tiny triangle at the tip."

Which nerve supplies the Anconeus?

The *Radial nerve*, same as Triceps — often considered a continuation of it. ⚡

Where is the Profunda brachii artery found?

Runs with the *Radial nerve in the radial groove* behind the humerus. Mnemonic: "Profunda = deep with Radial."

What does the Profunda brachii artery supply?

The *Triceps and posterior arm. It's the main deep branch of the Brachial artery*. 💉

What is the Radial groove?

A shallow groove on the back of the humerus where the *Radial nerve and Profunda brachii artery* travel together. ⚡

Where is the Radial nerve located in the arm?

Starts posteriorly with Triceps → passes through the *radial groove → then enters the anterior compartment* near the elbow. 🎯

What happens if the Radial nerve is injured in the arm?

Leads to *wrist drop* (inability to extend wrist/fingers) and numbness on the back of the hand. ⚠️ Mnemonic: "Radial = Raise hand → wrist drop."

Where is the Medial head of Triceps?

Deep to the long and lateral heads visible on cross-sections as the innermost muscle mass of the posterior arm.

What separates the arm into compartments?

The *lateral and medial intermuscular septa divide the arm into anterior (flexor) and posterior (extensor)* compartments. ⚖️

Where is the olecranon?

The *bony tip of the elbow* — insertion site of Triceps. Feels like a pointy bump behind the elbow.

What forms the posterior wall of the cubital region?

The *Triceps and Anconeus* muscles form it.

What arteries supply the elbow joint?

A network of *collateral and recurrent arteries* around the elbow → ensures continuous flow during bending. 🔄

On Anatomage

• Open Regio cubiti anterior/posterior

• Look for the arterial network surrounding the humeral epicondyles.

  • Lateral side = Radial collateral ↔ Radial recurrent

  • Posterior = Middle collateral ↔ Interosseous recurrent

  • Medial side (front/back) = Superior & Inferior ulnar collaterals ↔ Ulnar recurrents

What are the main collateral arteries?

*Superior and Inferior ulnar collateral arteries (from brachial) and Middle and Radial collateral arteries* (from profunda brachii). Mnemonic: "Super Inferior, Middle Radial."

What are the recurrent arteries?

*Radial, Ulnar, and Interosseous recurrent arteries* — they anastomose with collaterals around the elbow.

What's the clinical importance of the elbow anastomosis?

It maintains blood flow even when the elbow is flexed and compresses major arteries. 🔁

Where is the Lateral epicondyle?

The *outer bony bump of the distal humerus origin of wrist and finger extensors*. ⚙️

Where is the Medial epicondyle?

The *inner bump origin of wrist and finger flexors and a landmark for the Ulnar nerve*. 📍 Mnemonic: "Funny bone bump."

What does the Posterior cutaneous nerve of the arm supply?

The *skin on the back of the arm*, branch of the Radial nerve.

Where does the Radial nerve divide?

In front of the *lateral epicondyle, into Superficial (sensory) and Deep (motor)* branches. ⚡

What does the Deep branch of the Radial nerve become?

It becomes the *Posterior interosseous nerve (PIN)* — supplies forearm extensors. Mnemonic: "Deep dives → PIN."

What does the Superficial branch of the Radial nerve supply?

Purely sensory — supplies skin on the back of the hand and thumb base. ✋

What is the landmark for the Radial nerve on Anatomage?

Follow it between *lateral and long heads of Triceps*, spiraling toward the lateral epicondyle. It looks like a bright yellow cable. ⚡

Where can the Radial nerve be compressed?

In *mid-shaft humerus fractures* or by prolonged pressure ("Saturday night palsy"). ⚠️ Mnemonic: "Sleep on it → wrist drop."

What's the best way to identify Triceps on Anatomage?

Posterior view: three heads merging onto the *olecranon*, with yellow radial nerve winding behind them. 🎯