Extrinsic muscles of the wrist of the wrist and hand

Question

Muscles that originates externally to the hand (on the humerus, ulnar , or radius ) and insert within the
hand are referred to as extrinsic muscles of the hand.
Anterior Muscles
The four muscles originates on the medial epicondyle of the humerus on a structure known as common
flexor tendon.
• Flexor carpi radialis
• Flexor carpi ulnaris
• Flexor digitorum superficialis
• Palmaris longus
• Flexor digitorum profundus (not attached to the common flexor tendon)
7
Extrinsic muscles of the wrist of the wrist and hand
Posterior Muscles
Six major of the hand and wrist appear on the posterior (dorsal) surface of the forearm. Four of these
muscles originate on the lateral epicondyle of the humerus on a structure known as the common extensor
tendon:
• Extensor carpi radialis brevis
• Extensor digitorum (communis)
• Extensor carpi ulnaris
• Extensor digiti minimi (proprius)
The fifth and sixth muscles are the extensor
• Extensor carpi radialis longus
• Extensor indicis
8
Intrinsic muscles of the wrist and hand
The following muscles are the intrinsic of the hand and insert within the hand . Three of these muscles
make up an anatomical structure known as the hypothenar eminence.
• Abductor digiti minimi
• Flexor digiti minimi brevis
• Opponents digiti minimi
Several muscles of the hand are not involved with movement of the fifth finger but are involved in the
movement other finger joints. These muscles appear are three distinct muscle groups:
• Dorsal interossei
• Palmar interossei
• Lumbricales
9
Intrinsic muscles of the wrist and hand
The following muscles are the intrinsic of the hand and insert within the hand . Three of these muscles
make up an anatomical structure known as the hypothenar eminence.
• Abductor digiti minimi
• Flexor digiti minimi brevis
• Opponents digiti minimi
Several muscles of the hand are not involved with movement of the fifth finger but are involved in the
movement other finger joints. These muscles appear are three distinct muscle groups:
• Dorsal interossei
• Palmar interossei
• Lumbricales
10
Muscles of the thumb
Extrinsic muscles
The muscles all originate extrinsically , proximal to the thumb , and insert within the thumb.
• Extensor pollicis longus
• Extensor pollicis brevis (tendons of extensor pollicis brevis and the abductor pollicis longus. This
depression is commonly as the anatomical snuffbox)
• Abductor pollicis longus
• Flexor pollicis longus
Intrinsic muscles
• Flexor pollicis brevis
• Abductor pollicis brevis
• Opponens pollicis
• Adductor pollicis

Answer 1

The wrist and hand are supported by a complex system of muscles, which can be categorized into extrinsic and intrinsic muscles. Here’s a summary of those muscles:

Extrinsic Muscles of the Wrist and Hand

Anterior (Flexor) Muscles
These muscles originate on the medial epicondyle of the humerus and insert into the hand. They primarily function to flex the wrist and fingers. The key muscles include:

1. Flexor Carpi Radialis - Flexes and abducts the wrist.
2. Flexor Carpi Ulnaris - Flexes and adducts the wrist.
3. Flexor Digitorum Superficialis - Flexes the proximal interphalangeal joints and assists in flexing the wrist.
4. Palmaris Longus - Assists in flexing the wrist (absent in some individuals).
5. Flexor Digitorum Profundus - Flexes the distal interphalangeal joints (note: does not originate from the common flexor tendon).

Posterior (Extensor) Muscles
These muscles originate on the lateral epicondyle of the humerus and insert into the hand. They primarily function to extend the wrist and fingers. The main muscles include:

1. Extensor Carpi Radialis Brevis - Extends and abducts the wrist.
2. Extensor Digitorum (Communis) - Extends the fingers.
3. Extensor Carpi Ulnaris - Extends and adducts the wrist.
4. Extensor Digiti Minimi (Proprius) - Extends the little finger.
5. Extensor Carpi Radialis Longus - Extends and abducts the wrist.
6. Extensor Indicis - Extends the index finger.

Intrinsic Muscles of the Wrist and Hand

The intrinsic muscles originate and insert within the hand itself and are responsible for finer motor control. Notably, the intrinsic muscles can be divided into groups:

Hypothenar Eminence Muscles
These three muscles control movements of the little finger:

1. Abductor Digiti Minimi - Abducts the little finger.
2. Flexor Digiti Minimi Brevis - Flexes the little finger.
3. Opponens Digiti Minimi - Allows opposition of the little finger.

Interosseous Muscles
These muscles operate between the bones of the hand and include:

1. Dorsal Interossei - Abduct the fingers away from the midline of the hand.
2. Palmar Interossei - Adduct the fingers towards the midline of the hand.
3. Lumbricales - Flex the metacarpophalangeal joints while extending the interphalangeal joints.

Muscles of the Thumb

Extrinsic Muscles
The following muscles originate outside of the thumb and facilitate its movement:

1. Extensor Pollicis Longus - Extends the thumb.
2. Extensor Pollicis Brevis - Extends the proximal phalanx of the thumb.
3. Abductor Pollicis Longus - Abducts and extends the thumb.
4. Flexor Pollicis Longus - Flexes the thumb.

Intrinsic Muscles
Focusing specifically on the thumb, these muscles originate and insert within the hand:

1. Flexor Pollicis Brevis - Flexes the thumb.
2. Abductor Pollicis Brevis - Abducts the thumb.
3. Opponens Pollicis - Allows opposition of the thumb.
4. Adductor Pollicis - Adducts the thumb.

This system of muscles plays crucial roles in various functions, from gross movements like gripping and lifting to precise tasks requiring fine motor control.