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Questions and Answers
Which structure of the distal humerus is primarily associated with the attachment of flexor muscles?
What is the primary function of the MP (metacarpophalangeal) joints?
Which muscle group is responsible for wrist extension?
Which nerve innervates the majority of the flexor muscles located in the forearm?
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Which of the following structures is NOT found on the distal humerus?
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Which of the following muscles is responsible for forearm supination?
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What is the primary function of the thenar group of muscles?
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Which nerve innervates the intrinsic muscles of the hypothenar group?
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Which muscle is NOT part of the deep group of forearm extensors?
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Which of the following muscles is primarily responsible for abduction of the wrist?
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Which group of muscles is innervated by both the median and ulnar nerves?
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What is one common function of the interossei muscles?
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Which intrinsic muscle of the hand primarily functions in adducting the thumb?
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Which muscle is not primarily innervated by the median nerve in the anterior compartment of the forearm?
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What function do the muscles of the anterior compartment of the forearm NOT perform?
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Which of the following muscles acts as a depressor muscle but is derived from the posterior compartment?
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What action is primarily performed by the brachioradialis muscle?
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Which of the following muscles is in the deep layer of the anterior compartment of the forearm?
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Which nerve is responsible for innervating both the flexor carpi ulnaris and the medial half of the flexor digitorum profundus?
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What is the primary action of the muscles in the posterior compartment of the forearm?
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Which of the following muscles is specifically involved in the abduction of the wrist?
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Study Notes
Forearm Muscles
- The forearm muscles are divided into two compartments: the anterior compartment and the posterior compartment. The anterior compartment contains the depressor muscles, which are responsible for flexing the wrist and digits, abducting and adducting the wrist, and pronating the forearm and hand. The posterior compartment contains the elevator muscles, which are responsible for extending the wrist and digits, abducting and adducting the wrist, and supinating the forearm and hand.
Anterior Compartment
- The anterior compartment of the forearm contains three layers of muscles: superficial, middle, and deep.
- All the depressor muscles of the forearm are innervated by the median nerve except for the flexor carpi ulnaris and the medial half of the flexor digitorum profundus muscles, which are supplied by the ulnar nerve.
- The brachioradialis muscle, while acting as a depressor muscle, is derived from the posterior compartment and is innervated by the radial nerve.
Superficial Layer
- Brachioradialis: This muscle is responsible for flexing the forearm.
- Pronator Teres: This muscle pronates the forearm.
- Flexor Carpi Radialis: This muscle flexes and abducts the wrist.
- Palmaris Longus: This muscle flexes the wrist and tenses the palmar fascia.
- Flexor Carpi Ulnaris: This muscle flexes and adducts the wrist.
Middle Layer
- Flexor Digitorum Superficialis: This muscle flexes the proximal interphalangeal joints of digits 2-5 (middle finger, ring finger, little finger).
Deep Layer
- Flexor Digitorum Profundus: This muscle flexes the distal interphalangeal joints of digits 2-5 (middle finger, ring finger, little finger).
- Flexor Pollicis Longus: This muscle flexes the distal interphalangeal joint of the thumb.
- Pronator Quadratus: This muscle pronates the forearm.
Posterior Compartment
- The elevator muscles of the forearm are all innervated by the radial nerve (deep branch of the radial nerve).
Superficial Group
- Brachioradialis: This muscle flexes the forearm.
- Extensor Carpi Radialis Longus: This muscle extends and abducts the wrist.
- Extensor Carpi Radialis Brevis: This muscle extends and abducts the wrist.
- Extensor Carpi Ulnaris: This muscle extends and adducts the wrist.
- Extensor Digitorum: This muscle extends the metacarpophalangeal and proximal interphalangeal joints of digits 2-5.
- Extensor Digiti Minimi: This muscle extends the metacarpophalangeal and proximal interphalangeal joints of the little finger.
Deep Group
- Supinator: This muscle supinates the forearm
- Abductor Pollicis Longus: This muscle abducts the thumb.
- Extensor Pollicis Longus: This muscle extends the thumb.
- Extensor Pollicis Brevis: This muscle extends the thumb.
- Extensor Indicis: This muscle extends the index finger.
Intrinsic Muscles of the Hand
- Intrinsic muscles of the hand are responsible for fine motor movements of the hand.
- They are located within the hand and are divided into five groups: thenar, hypothenar, lumbricals, interossei, and adductor pollicis.
Thenar Group
- The thenar group of muscles are responsible for opposition of the thumb, allowing it to touch the other fingers. These muscles are innervated by a branch of the median nerve.
- The abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis muscles are part of the thenar group.
Hypothenar Group
- The hypothenar group of muscles are responsible for movements of the little finger. They are innervated by the ulnar nerve.
- The abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi muscles are part of the hypothenar group.
Lumbricals
- The lumbricals are four small muscles that flex the metacarpophalangeal joints and extend the proximal interphalangeal joints of digits 2-5.
- The first two lumbricals are innervated by the median nerve, and the last two are innervated by the ulnar nerve.
Interossei
- The interossei muscles are responsible for adduction and abduction of the fingers. They are innervated by the ulnar nerve.
- The dorsal interossei muscles abduct the fingers, and the palmar interossei muscles adduct the fingers.
Adductor Pollicis
- The adductor pollicis muscle is responsible for adducting the thumb. It is innervated by the ulnar nerve.
Distal Humerus
- The distal humerus is the lower end of the humerus bone.
- It contains several important landmarks, including the medial epicondyle, lateral epicondyle, trochlea, capitulum, olecranon fossa, and coronoid fossa.
The Role of the Distal Humerus
- The medial epicondyle provides attachment points for the forearm muscles that flex the wrist and digits.
- The lateral epicondyle provides attachment points for the forearm muscles that extend the wrist and digits.
- The trochlea is a smooth, pulley-shaped articular surface that articulates with the ulna.
- The capitulum is a small, rounded articular surface that articulates with the radius.
- The olecranon fossa is a deep depression on the posterior surface of the distal humerus that receives the olecranon process of the ulna during elbow extension.
- The coronoid fossa is a shallow depression on the anterior surface of the distal humerus that receives the coronoid process of the ulna during elbow flexion.
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