Human Anatomy Joint Quiz

Extensor Compartment of the Forearm

• Muscles of the extensor compartment originate from the lateral epicondyle.
• The common origin of these muscles is the lateral side.
• The axillary artery branches into the brachial artery, used for measuring blood pressure.
• The radial nerve innervates the extensor muscles.
• Brachioradialis, despite being in the extensor compartment, is a flexor of the elbow and is supplied by the radial nerve.
• Extensor carpi radialis, longus, and brevis extend the wrist (carpal bones) with long tendons.
• The radial nerve runs anteriorly, then behind the supinator muscle (at the radio-ulnar joint). Supination occurs exclusively at the radio-ulnar joint.

Supinator Muscle

• The supinator rotates the forearm (supination) at the radio-ulnar joint.

Deep Branch of Radial Nerve

• The deep branch of the radial nerve becomes the posterior interosseous nerve.
• The posterior interosseous nerve travels with the posterior interosseous artery.
• The posterior interosseous artery branches off from the ulnar artery.
• The ulnar artery also gives rise to the common interosseous artery, which divides into the anterior and posterior interosseous arteries.
• The radial nerve, supplying extensor muscles, gives rise to the posterior interosseous nerve.
• The common interosseous artery, originating from the ulnar artery, branches into the anterior and posterior interosseous arteries.
• The median nerve gives rise to the anterior interosseous nerve.

Flexor Carpi Radialis

• The flexor carpi radialis is used to feel a pulse, which is felt laterally.

Important Anatomical Landmarks

• Styloid process, scaphoid, and the base of the first metacarpal are important landmarks.
• The radial artery crosses these structures.
• The ulnar nerve supplies 1.5 fingers.
• Frequent fractures occur to the scaphoid.
• The lunate bone is a common site for wrist dislocations.

Clinical Relevance: Elbow and Wrist

• Lateral epicondylitis (tennis elbow) affects extensor muscles, and involves inflammation of the entire bone.
• Medial epicondylitis (golfer's elbow), synovial cysts, or mallet finger, affect flexor muscles.
• Radial nerve injury causes wrist drop (loss of wrist extension).
• Damage at different points (proximal or distal) affects different nerves.

Hand Muscles and Innervation

• Unique hand movement is opposition.
• Palmar aponeurosis extends to the digits.
• For exams, focus on innervation and actions rather than origins/insertions (names often indicate the action).
• Abductor pollicis longus is in the extensor compartment, supplied by the radial nerve, and spared if damage occurs to recurrent branch.
• Abductor pollicis brevis, flexor pollicis longus, and the other three thenar muscles are innervated by the recurrent branch of the median nerve.
• The ulnar nerve primarily innervates the hand, not thenar muscles.

Lumbricals

• Lumbricals originate from the flexor digitorum profundus tendons.
• Lumbricals are partly (½) supplied by the median nerve and partly (¾) by the ulnar nerve.
• They sit on the extensor expansion.
• Actions: flex MP joint, extend IP joints.
• Originate from the flexor digitorum profundus tendons

Interosseous Muscles

• Dorsal and palmar interosseous muscles are supplied by the ulnar nerve.

Arteries and Veins of the Hand

• The ulnar artery forms the superficial palmar arch.
• The radial artery forms the deep palmar arterial arch.
• All these are superficial veins: cephalic, basilic, median.
• Median cubital vein connects cephalic and basilic veins for blood withdrawal.
• Deep veins accompany arteries (venae comitantes).

Nerves of the Palm and fingers

• The median nerve passes through the carpal tunnel.
• The ulnar nerve supplies adductor pollicis, half of the lumbricals, eight interossei, the hypothenar eminence, and the dorsal and palmar aspects of half of the fingers.

Nerve Innervation and Exam Considerations

• The radial side of the dorsal hand is supplied 3/5 by the radial nerve, while the ulnar nerve supplies 1/2 for both sides. In palmar side, half of the palm and fingers is supported by ulnar nerve.
• Damage to the median nerve in the index finger affects the ulnar side of the index finger.
• The recurrent branch supplies thenar muscles and three-fifths of the digits, but not the adductor pollicis.
• The ulnar nerve can be damaged at the medial epicondyle and the cubital tunnel (FCU).
• Guyon's canal lies next to the pisiform and hamate bones.
• Ulnar nerve injury causes claw hand.
• Common occupational injuries include carpal tunnel syndrome.
• Ulnar nerve injury at the wrist affects adductor muscles, hypothenar muscles, 2 lumbricals, and all interosseous muscles.
• Hand benediction (drop): injury to the median nerve in the elbow

Joints

• All joints have cartilaginous coverings at both ends of the bones.
• Joint capsules surround each joint.
• Synovial membranes secrete a fluid for smooth movement.
• Glenohumeral joint is the most mobile joint.
• Rotator cuff attaches to greater tuberosity of humerus.
• Suprascapularis (of the rotator cuff) is the only muscle to not rotate the arm.
• Thicker portions of the capsule are ligaments.
• Shoulder dislocation often occurs anteriorly.
• Superior dislocations of the shoulder are less frequent than inferior.

Fracture and Dislocations

• Axillary and radial nerve are commonly injured at the shoulder.
• Colle's fracture: common fracture of the distal end of the radius, with posterior displacement of the fragment.
• Wrist joint allows circumduction movement.
• Scaphoid is the most common wrist bone fracture.
• Lunate is the most commonly dislocated wrist bone.
• Radio-ulnar joint: Annular ligament holds radius head against ulna, enabling pronation and supination.
• Subluxation: Annular ligament injury causes radius head to stand out; fix by supination.

Skeletal Structures

• Example of structures in the anatomical box: styloid process of radius, metacarpal, and scaphoid.
• The most commonly fractured bone is the scaphoid.

Different Joint Types

• Plane/Gliding Joints: allow sliding motion (carpal and tarsal bones, costovertebral joints )
• Hinge Joints: permit angular motion (elbow, knee, interphalangeal).
• Saddle Joints: allow back-and-forth and side-to-side motion (e.g., carpometacarpal joint of the thumb).
• Condyloid/Ellipsoid Joints: allow movement along two axes (wrist, metacarpophalangeal joints).
• Ball-and-Socket Joints: enable rotational movement (shoulder, hip).
• Pivot Joints: enable rotation around a single axis (atlantoaxial, radioulnar).

Pronation and Supination

• Pronation: controlled by pronator teres and pronator quadratus in the forearm.
• Supination: driven by biceps brachii (with more power needed) and supinator. (resistance is absent)