What are the three articulations that make up the elbow joint and their joint types?
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What are the three articulations that make up the elbow joint and their joint types?
Which muscles primarily produce elbow flexion and their innervation?
Biceps brachii (musculocutaneous n.), brachialis (musculocutaneous; also radial contributions), and brachioradialis (radial n.).
Which muscle produces primary elbow extension and its innervation?
Triceps brachii — innervated by the radial nerve.
Name the major anatomical features of the radius.
Head, neck, radial tuberosity (attachment for biceps), oblique line, and radial styloid process.
Name the major anatomical features of the ulna.
Olecranon, coronoid process, trochlear (semilunar) notch, radial notch, ulnar tuberosity, and ulnar styloid process.
Which carpal bone is most frequently fractured and is located in the anatomical snuff box?
The scaphoid—it lies in the anatomical snuff box and is prone to fracture.
Where is the lunate located and why is it clinically important?
The lunate is a central proximal-row carpal bone that articulates with the radius and is commonly involved in wrist dislocations.
How are the metacarpals and phalanges numbered and what phalangeal types exist?
Metacarpals/phalanges are numbered 1–5 (thumb = 1). Phalanges: proximal, middle (except thumb), and distal.
What is the significance of the supinator muscle in relation to the radial nerve?
The supinator forms the floor of the cubital fossa and is pierced by the deep branch of the radial nerve (which becomes posterior interosseous).
What important structure passes through the anatomical snuff box?
The radial artery passes through the anatomical snuff box; the snuff box is bounded by EPL (medial) and APL/EPB (lateral).
Which deep posterior muscles form the boundaries of the anatomical snuff box?
Abductor pollicis longus and extensor pollicis brevis form the lateral (radial) border, and extensor pollicis longus forms the medial border of the anatomical snuff box.
Where is the extensor indicis located relative to the extensor pollicis longus?
Extensor indicis is parallel and medial to the extensor pollicis longus.
Which muscles supinate and pronate the forearm and their innervations?
Supination: biceps brachii (musculocutaneous) and supinator (deep branch of radial). Pronation: pronator teres (median) and pronator quadratus (anterior interosseous branch of median).
What are the anatomical boundaries of the cubital fossa?
Medial border: pronator teres; lateral border: brachioradialis; superior border: line between the medial and lateral epicondyles (epicondylar line).
List the main contents of the cubital fossa from lateral to medial.
Lateral → medial: radial nerve (and branches), biceps tendon, brachial artery, median nerve.
Which superficial veins are commonly seen at the cubital fossa used for venipuncture?
The cephalic vein, basilic vein, and median cubital vein.
What separates the anterior and posterior compartments of the forearm and what are their primary functions?
The interosseous membrane separates them. Anterior compartment: wrist flexion & pronation (median nerve). Posterior compartment: wrist/digit extension & supination (radial nerve).
Name the four muscles of the superficial layer of the anterior forearm and the innervation exception.
Pronator teres, Flexor carpi radialis, Palmaris longus, Flexor carpi ulnaris. Innervation: median nerve for most; flexor carpi ulnaris is innervated by the ulnar nerve.
Describe the anatomical relationship between the median nerve and pronator teres.
The median nerve passes between the two heads of pronator teres as it enters the forearm.
What is special about the course and insertion of flexor carpi radialis?
Flexor carpi radialis passes through its own compartment of the flexor retinaculum and inserts on the base of the 2nd metacarpal.
Where does the palmaris longus lie relative to the flexor retinaculum and how common is its absence?
Palmaris longus passes superficial to the flexor retinaculum and is absent in approximately 14% of limbs.
Which nerve innervates flexor carpi ulnaris?
The ulnar nerve innervates flexor carpi ulnaris.
What is the action and innervation of flexor digitorum superficialis?
Flexes the middle phalanges at the PIP joints of digits 2–5 and assists at MCP joints; innervated by the median nerve.
Which muscles form the deep layer of the anterior compartment and their general innervation?
Flexor digitorum profundus, flexor pollicis longus, and pronator quadratus — primarily innervated by the anterior interosseous branch of the median nerve, except the medial portion of FDP (ulnar nerve).
How is the innervation of flexor digitorum profundus divided?
Lateral (radial) half of FDP → anterior interosseous (median); medial half → ulnar nerve.
What is the relationship between the radial artery and flexor pollicis longus?
The radial artery lies on the anterior surface of the flexor pollicis longus muscle.
Where do the anterior interosseous nerve and artery run relative to pronator quadratus?
They pass posterior to the pronator quadratus muscle.
What deficit results from anterior interosseous nerve entrapment?
Paralysis of flexor pollicis longus and lateral FDP → inability to form an OK sign (abnormal pinch sign). Thenar muscles and cutaneous sensation are preserved.
How does the ulnar nerve enter the forearm and which forearm muscles does it supply?
It passes posterior to the medial epicondyle to enter the forearm and supplies flexor carpi ulnaris and the medial portion of flexor digitorum profundus (1.5 muscles).
Which nerve supplies the posterior (extensor) compartment of the forearm?
The radial nerve (and its branches, deep/posterior interosseous) supplies the extensor-supinator compartment.
List the six superficial layer muscles of the posterior forearm.
Brachioradialis, Extensor carpi radialis longus, Extensor carpi radialis brevis, Extensor digitorum, Extensor digiti minimi, Extensor carpi ulnaris. Innervation: radial nerve (or its deep branch).
What is notable about the brachioradialis within the extensor group?
Brachioradialis is the most anterior member of the extensor group and acts as a relatively weak flexor when the forearm is midpronated.
To which metacarpal does extensor carpi radialis longus attach?
Extensor carpi radialis longus attaches to the base of the 2nd metacarpal.
Where does extensor carpi radialis brevis originate and insert?
It arises from the common extensor tendon (lateral epicondyle) and inserts on the base of the 3rd metacarpal.
Describe the tendon arrangement of extensor digitorum.
Extensor digitorum gives rise to four tendons with intertendinous connections between them for the medial four digits.
What is the origin of extensor digiti minimi?
Extensor digiti minimi arises from the ulnar side of the extensor digitorum and assists extension of the 5th digit.
Which muscle is the most medial in the superficial posterior compartment?
Extensor carpi ulnaris is the most medial superficial extensor muscle.
What forms the roof of the carpal tunnel and what bones form its borders?
The flexor retinaculum (transverse carpal ligament) forms the roof. The carpal bones form the floor and sides (pisiform & hook of hamate medially; scaphoid & trapezium laterally).
What are the contents of the carpal tunnel?
Nine flexor tendons (FDS and FDP tendons for digits 2–5, FPL) and the median nerve pass through the carpal tunnel.
Which muscles make up the thenar eminence and their innervation?
Abductor pollicis brevis, Flexor pollicis brevis, Opponens pollicis — innervated by the recurrent branch of the median nerve.
Which muscles comprise the hypothenar eminence and their innervation?
Abductor digiti minimi, Flexor digiti minimi brevis, Opponens digiti minimi — innervated by the deep branch of the ulnar nerve.
Describe lumbrical attachments and their innervation pattern.
Lumbricals attach from FDP tendons to the extensor expansions of digits 2–5. Lumbricals 1–2: median nerve (unipennate). Lumbricals 3–4: ulnar nerve (deep branch, bipennate).
Which intrinsic thumb muscle is innervated by the ulnar nerve?
Adductor pollicis is the only intrinsic thumb muscle innervated by the ulnar nerve.
Compare palmar and dorsal interossei: actions, number, and innervation.
Palmar interossei (3): adduct digits toward axial line (PAD), unipennate. Dorsal interossei (4): abduct digits away from axial line (DAB), bipennate. Both innervated by the ulnar nerve (deep branch).
Summarize the ulnar nerve motor and cutaneous distribution in the hand.
Motor: most intrinsic hand muscles except thenar, lateral FDP, and first two lumbricals. Cutaneous: medial palm and medial dorsum of hand including medial 1.5 digits. It passes through Guyon's canal.
Which hand muscles and skin areas does the median nerve supply?
Motor: thenar eminence (recurrent branch) and lateral two lumbricals. Cutaneous: lateral palmar hand and lateral 3.5 digits.
What is the role of the radial nerve in hand innervation?
The radial nerve supplies only extrinsic extensor musculature via the posterior interosseous nerve (no intrinsic hand muscles) and provides cutaneous innervation to posterior arm/forearm and lateral dorsal hand (lateral 3.5 digits).
Which muscles produce wrist flexion and their innervation?
Flexor carpi radialis and palmaris longus (median nerve) and flexor carpi ulnaris (ulnar nerve) produce wrist flexion.
Which muscles produce wrist extension and their innervation?
Extensor carpi radialis longus (radial n.), extensor carpi radialis brevis (deep branch of radial n.), and extensor carpi ulnaris (deep branch of radial n.) produce wrist extension.
Which muscles cause wrist abduction (radial deviation)?
Extensor carpi radialis longus & brevis and flexor carpi radialis cause wrist abduction (radial deviation).
Which muscles cause wrist adduction (ulnar deviation) and their innervation?
Extensor carpi ulnaris (deep branch of radial n.) and flexor carpi ulnaris (ulnar n.) cause wrist adduction.
