2.4.4. Anatomy Lab Thursday - Dorsum of Hand Flashcards by Don Rees

Identify the following:

Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor digitorum (communis)
Extensor digiti minimi
Extensor carpi ulnaris

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Identify the following:

Abductor pollicis longus
Extensor pollicis brevis
Extensor carpi radialis brevis
Extensor digitorum (communis)

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Identify the following:

Extensor pollicis longus
Extensor indicis proprius
Supinator
Abductor pollicis longus
Extensor pollicis brevis
Radius

Note: The more superficial extensors of the forearm have been cut and removed/reflected to show the deeper extensors

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Identify the following:

Extensor retinaculum
Junctura (connecting band between extensor tendons)
Extensor digiti minimi
Dorsal interosseous

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Identify the following:

What is this region commonly referred to as?

Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
Radial artery

This region is referred to as the anatomical snuff box. The radial artery passes through the “snuff box” and the scaphoid bone is located in the floor of the “snuff box.”

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Extensor digitorum quinti (EDQ):

Origin

Insertion

Innervation

Action

Origin: Lateral epicondyle of humerus

Insertion: Extensor expansion of 5th digit

Innervation: Deep branch of radial nerve (C7, C8)

Action: Extends 5th digit

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Extensor carpi ulnaris (ECU):

Origin

Insertion

Innervation

Action

Origin: lateral epicondyle of humerus, posterior border of ulna via shared aponeurosis

Insertion: dorsal aspect of base of 5th metacarpal

Innervation: deep branch of radial nerve (C7, C8)

Action: extends and adducts hand at wrist joint (involved with clenching too)

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Extensor digitorum (ED):

Origin

Insertion

Innervation

Action

Origin: lateral epicondyle of humerus

Insertion: extensor expansions of medial four digits

Innervation: deep branch of radial nerve (C7, C8)

Action: extends medial four digits

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Extensor carpi radialis brevis (ECRS):

Origin

Insertion

Innervation

Action

Origin: lateral epicondyle of humerus

Insertion: dorsal aspect of base of 3rd metacarpal

Innervation: deep branch of radial nerve (C7, C8)

Action: extend and adduct hand at wrist joint

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Extensor Carpi Radialis Longus (ECRL):

Origin
Insertion

Innervation

Action

Origin: lateral supra-epicondylar ridge of the humerus

Insertion: dorsal aspect of base of 2nd metacarpal

Innervation: radial nerve (C6, C7)

Action: extend and adduct hand at wrist joint, active during fist clenching

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Brachioradialis:

Origin

Insertion

Innervation

Action

Origin: proximal two thirds of supra-epicondylar ridge of humerus

Insertion: lateral surface of distal end of radius proximal to styloid process

Innervation: Radial nerve (C5, C6, C7)

Action: weak flexion of forearm maximal when forearm in mid pronator position

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Extensor pollicis longus (EPL):

Origin

Insertion

Innervation

Action

Origin: posterior surface of middle third of ulna and interosseus membrane

Insertion: dorsal aspect of base of distal phalanx of thumb

Innervation: posterior interosseus nerve (C7, C8) (continuation of deep branch of radial nerve)

Action: extends distal phalanx at thumb

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Abductor pollicis longus (APL):

Origin

Insertion

Innervation

Action

Origin: posterior surface of proximal halves of ulna, radius, and interossues membrane

Insertion: base of 1st metacarpal

Innervation: posterior interosseus nerve (C7, C8)

Action: abducts and extends thumb

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Extensor pollicis brevis (EPB):

Origin

Insertion

Innervation

Action

Origin: posterior surface of distal third of radius and interosseus membrane

Insertion: dorsal aspect of base of proximal phalanx of thumb

Innervation: posterior interosseus nerve (C7, C8)

Action: extends proximal phalanx of thumb

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Extensor Indicis Proprius (EIP):

Origin

Insertion

Innervation

Action

Origin - posterior surface of distal third of ulna and interosseus membrane

Insertion - extensor expansion of 2nd digit

Innervation - posterior interosseus nerve (C7, C8)

Action - extends 2nd digit (enabling its independent extension), helps extend hand at wrist

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Supinator:

Origin

Insertion

Innervation

Action

Origin - lateral epicondyle of humerus, radial collateral and annular ligaments, supinator fossa, crest of ulna

Insertion - lateral, posterior, and anterior surfaces of proximal third of radius

Innervation - deep branch of radial nerve (C7, **C8**)

Action - supinates forearm, rotates radius to turn palm anteriorly or superiorly if the elbow is flexed

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Tenderness in the anatomical snuff box is a indicator of what?

Scaphoid fracture

The primary extensor of the distal interphalangeal joint (DIPJ) for each finger is what?

The flexor digitorum profundus (FDP)

Explain the general way in which digits are flexed and extended.

Although any motor unit (muscle or tendon) that crosses a joint can move that joint, the metacarpophalangeal joint (MPJ) is primarily flexed by the interossei and extended by the extensor digitorum communis (ED or EDC).
The proximal interphalangeal joint (PIPJ) is primarily flexed by the flexor digitorum superficialis (FDS) and extended by the interossei (this is especially true when the PIPJ is extended while the MPJ is in the flexed position).
The distal interphalangeal joint (DIPJ) is flexed by the flexor digitorum profundus (FDP) and extended by the interossei*.*The lumbricals do assist the interossei, but they are so small in comparison that the interossei do most of the work

Explain how the thumb is flexed and extended.

The MPJ here is primarily flexed by the thenar muscles and extended by the

extensor pollicis brevis (EPB). The IPJ is flexed by the flexor pollicis longus (FPL) and

extended by the extensor pollicis longus (EPL). The thenar muscles (like the interossei

muscles of the fingers) can also extend the IPJ - especially when the MPJ is already

flexed.

Prime flexor and extensor of the MPJ (metacarpophalangeal joint)?

Prime flexor: interossei muscles and weak assistance from the lumbricals

Prime extensor: EDC via the sagittal bands

Prime flexor and extensor of the PIPJ (proximal interphalangeal joint)?

Flexor: FDS

Extensor: Interossei muscles and weak assistance from the lumbricals via the lateral bands

Prime flexor and extensor for the DIPJ (distal interphalangeal joint)?

Flexor: FDP

Extensor: Interossei and weak assistance from the lumbricals through the lateral bands

Which nerve mediates fine, rapid, coordinated movements of the fingers, especially when the fingers are in the “functional” or “ready” position?

The ulnar nerve

With the elbow bent, what is the strongest supinator, and why?

The biceps brachii, because of where it attaches (the radial tuberosity)

Any tendon that crosses a joint has the capability to do what?

Move that joint, even if it is not considered to be the "prime" mover of the joint. This can be especially important for patients who have lost some (but not all) due to an accident or IED.

The power (force) of a muscle is proportional to what?

The cross-sectional area of the muscle

The deep (motor) branch of the radial nerve is renamed as the __________ after it exits \_\_\_\_\_\_\_\_\_\_.

The posterior interosseous nerve after it exits the supinator muscle distally

What should you do if you think your patient has a scaphoid fracture, but the X-ray does not show one?

Treat them as if they have the fracture! Sometimes scaphoid fractures will not show up on X-ray until a week later.

From the anterior aspect, what wrist movement makes the tubercle of the scaphoid "pop up" and makes it easy to palpate?

Radial deviation

Which extensor compartment of the wrist provides the anatomically-safest surgical access to the tendons and the interior of the wrist joint?

The fourth dorsal compartment; it offers a convenient ansd safe portal since there are few nerves, vessels, and critical ligaments that are damaged by this technique.

List the 6 Extrinsic muscles (originate outside the hand but insert within the hand by way of their tendons)

Extensor digitorum (communis) Extensor digiti minimi Abductor pollicis longus Extensor pollicis brevis Extensor pollicis longus Extensor indicis (proprius)

List the 9 intrinisic muscles of the hand (both originate and insert within the hand itself)

Abductor pollicis brevis Adductor pollicis brevis Flexor pollicis brevis Opponens pollicis Abductor digiti minimi Flexor digiti minimi brevis Opponens digiti minimi Lumbricals (4) Interossei (3 palmar, 4 dorsal)

Long term carpal tunnel syndrome can cause atrophy to which group of muscles & why?

The thenar muscles, because they are innervated by the median nerve (which is compressed in carpal tunnel)

What is the action of the dorsal interossei?

ABduction (think DAB)

What is the action of the palmar interossei?

ADduction (think PAD)

What does the ulnar nerve enter the hand through?

Guyon's canal (aka the ulnar canal)

True or false: When doing a procedure, you should never inject anything into the fingers.

True. Injections can cause too much compression and can cause irreversible nerve damage. Inject the hand instead. Anything distal to the injection site should feel the effects of anesthesia.

What two groups of muscles function to "cup" the hand?

The thenar and hypothenar muscles

To locate the scaphoid from the radial aspect, deviate your hand _______ while you feel for the scaphoid bone in your anatomical snuff box.

Ulnarly