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What factors justify the greater range of ulnar deviation compared to radial deviation of the wrist?
Radial deviation at the radiocarpal joint is limited because the radial side of the carpus impinges against the styloid process of the radius.
List all the muscles that have full or partial proximal attachment to the medial epicondyle of the humerus.
Pronator Teres, Flexor Digitorum Superficialis, Palmaris Longus, Flexor Carpi Radialis, Flexor Carpi Ulnaris.
Which nerve innervates the muscles attached to the medial epicondyle?
Median nerve (except for Flexor Carpi Ulnaris which is innervated by the Ulnar nerve).
What is the primary responsibility of the muscles of the hypothenar eminence?
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Which nerve innervates the muscles of the hypothenar eminence?
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Name all the responsible muscles for flexion at the carpometacarpal joint.
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Which muscles are the extrinsic extensors of the thumb?
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Describe the different muscles used for larger movements versus fine movements.
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Which digit has the greatest mass of intrinsic muscle and why?
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What are the 5 fascial compartments of the hand and which movements do they facilitate?
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Study Notes
Wrist Motion
- Ulnar deviation has a greater range of motion than radial deviation due to the radial side of the carpus impinging on the styloid process of the radius during radial deviation.
Muscles of the Medial Epicondyle
- The muscles attached to the medial epicondyle of the humerus are primarily involved in wrist flexion and forearm pronation.
- They are innervated by the median nerve, with the exception of the flexor carpi ulnaris, which is innervated by the ulnar nerve.
- These muscles include:
- Pronator teres: pronates and flexes the forearm
- Flexor digitorum superficialis: flexes the middle phalanges of the four middle fingers
- Palmaris longus: flexes the hand and tenses the palmar aponeurosis
- Flexor carpi radialis: flexes and abducts the hand
- Flexor carpi ulnaris: flexes and adducts the hand
Deep Branch of the Ulnar Nerve
- The deep branch of the ulnar nerve innervates a group of hand muscles responsible for various movements:
- Adductor pollicis: adducts the thumb
- Abductor digiti minimi: abducts the little finger
- Flexor digiti minimi: flexes the little finger
- Opponens digiti minimi: opposes the little finger
- Lumbricals 3 and 4: flex the metacarpophalangeal joints and extend the interphalangeal joints
- Dorsal interossei: abduct the fingers
- Palmar interossei: adduct the fingers
Hypothenar Eminence
- The muscles of the hypothenar eminence, innervated by the deep branch of the ulnar nerve, primarily control the little finger.
Flexion at the Carpometacarpal Joint
- The muscles responsible for flexion at the carpometacarpal joint are the opponens pollicis and opponens digiti minimi.
Extrinsic Extensors of the Thumb
- The extrinsic extensors of the thumb are innervated by the posterior interosseous nerve, which is a continuation of the deep radial nerve:
- Abductor pollicis longus
- Extensor pollicis brevis
- Extensor pollicis longus
Muscles for Large vs. Fine Movements
-
Larger/Wider Movements:
- Extrinsic muscles of the forearm (flexor digitorum superficialis, flexor digitorum profundus, extensor digitorum, flexor pollicis longus) provide strong force for grasping, pinching, and pointing.
- Intrinsic hand muscles (thenar and hypothenar) contribute to strong gripping and pinching.
- Dorsal interossei assist in spreading the fingers for grasping wider objects.
-
Fine and Weaker Movements:
- Intrinsic hand muscles (lumbricals, palmar interossei, thenar and hypothenar muscles) provide precise controlled motion for typing and writing.
- Lumbricals are essential for dexterity, flexing the metacarpophalangeal joints and extending the interphalangeal joints.
Intrinsic Muscles of the Thumb
- The thumb has the greatest mass of intrinsic muscles, allowing for precise and complex movements:
- Adductor pollicis: adducts the thumb
- Opponens pollicis: opposes the thumb
- Flexor pollicis brevis: flexes the thumb
- Abductor pollicis brevis: abducts the thumb
Fascial Compartments of the Hand
- The hand is divided into 5 fascial compartments, each facilitating specific movements:
- Thenar compartment: controls thumb movements (abduction, flexion, opposition)
- Hypothenar compartment: controls little finger movements (abduction, flexion, opposition)
- Central compartment: flexes the metacarpophalangeal joints and extends the interphalangeal joints for fine motor tasks (controlled by lumbricals)
- Adductor compartment: adducts the thumb for pinching and gripping
- Interosseous compartment: abducts and adducts the fingers and assists with finger flexion and extension.
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Description
Explore the biomechanics of wrist motion, focusing on ulnar and radial deviation. Understand the muscles attached to the medial epicondyle of the humerus and their roles in wrist flexion and forearm pronation, along with their nerve innervations.
