Structures
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Extensor retinaculum
- Is a thickening of the antebrachial fascia on the back of the wrist, is subdivided into compartments, and places the extensor tendons beneath it.
- Extends from the lateral margin of the radius to the styloid process of the ulna, the pisiform, and the triquetrum.
- Is crossed superficially by the superficial branch of the radial nerve.
Palmar aponeurosis
- Is a triangular fibrous layer overlying the tendons in the palm and is continuous with the palmaris longus tendon, the thenar and hypothenar fasciae, the flexor retinaculum, and the palmar carpal ligament.
- Protects the superficial palmar arterial arch, the palmar digital nerves, and the long flexor tendons.
Palmar carpal ligament
- Is a thickening of deep antebrachial fascia at the wrist, covering the tendons of the flexor muscles, median nerve, and ulnar artery and nerve, except palmar branches of the median and ulnar nerves.
Flexor retinaculum
- Serves as an origin for muscles of the thenar eminence.
- Forms the carpal (osteofascial) tunnel on the anterior aspect of the wrist.
- Is attached medially to the triquetrum, the pisiform, and the hook of the hamate and laterally to the tubercles of the scaphoid and trapezium.
- Is crossed superficially by the ulnar nerve, ulnar artery, palmaris longus tendon , and palmar cutaneous branch of the median nerve.
Carpal tunnel
- Is formed anteriorly by the flexor retinaculum and posteriorly by the carpal bones.
- Transmits the median nerve and the tendons of flexor pollicis longus, flexor digitorum profundus, and flexor digitorum superficialis muscles.
Fascial spaces of the palm
- Are fascial spaces deep to the palmar aponeurosis and divided by a midpalmar (oblique) septum into the thenar space and the midpalmar space.
Thenar space
- Is the lateral space that contains the flexor pollicis longus tendon and the other flexor tendons of the index finger.
Midpalmar space
- Is the medial space that contains the flexor tendons of the medial three digits.
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Synovial flexor sheaths
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Common synovial flexor sheath (ulnar bursa)
- Envelops or contains the tendons of both the flexor digitorum superficialis and profundus muscles.
Synovial sheath for flexor pollicis longus (radial bursa)
- Envelops the tendon of the flexor pollicis longus muscle.
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Tendons of the flexor and extensor digitorum muscles
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- The flexor digitorum superficialis tendon splits into two medial and lateral bands and inserts on the base of the middle phalanx, while the flexor digitorum profundus tendon inserts on the base of the distal phalanx as a single tendon. On the dorsum of the hand, a single central band of the extensor digitorum tendon inserts on the base of the middle phalanx, while two lateral bands of the extensor digitorum tendon join to form a single band to insert on the base of the distal phalanx.
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| Extensor expansion |
Extensor expansion
- Is the expansion of the extensor tendon over the metacarpophalangeal joint and is referred toby clinicians as the extensor hood.
- Provides the insertion of the lumbrical and interosseous muscles and the extensor indicis and extensor digiti minimi muscles.
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Anatomic snuffbox
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- Is a triangular interval bounded medially by the tendon of the extensor pollicis longus muscle and laterally by the tendons of the extensor pollicis brevis and abductor pollicis longus muscles.
- Is limited proximally by the styloid process of the radius.
- Has a floor formed by the scaphoid and trapezium bones and crossed by the radial artery.
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Fingernails
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- Are keratinized plates on the dorsum of the tips of the fingers that consist of the proximal hidden part or root , the exposed part or body , and the distal free border. Parts of the nail include:
- Nail bed. The skin underneath the nail is the nail bed in which sensory nerve endingsand blood vessels are abundant. The matrix or proximal part of the nail bed produces hard keratin and is responsible for nail growth.
- Other structures. The root is partially covered by a fold of skin known as the nail fold. The narrow band of epidermis prolonged from the proximal nail fold onto the nail is termed the eponychium . The half-moon, or lunula , is distal to the eponychium. The hyponychium represents the thickened epidermis deep to the distal end of the nail.
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