Dissector Answers - Flexor compartment of the forearm, Superficial Hand, and Elbow joint

Learning Objectives:

Upon completion of this session, the student will be able to:

  1. Identify the prominent features of the humerus, ulna, radius, carpals, metacarpals and phalanges of the associated extensor and flexor compartments as given in the lab manual. (explanation)
  2. Identify the flexor compartment of the forearm and hand, the nerve and vessels supplying their contents, and the functional significance of the included muscles. (explanation)
  3. Correlate any fractures or deep cuts of the forearm or hand with functional disruptions of associated muscular or neurovascular structures. (explanation)
  4. Describe the movements of elbow, wrist, and finger joints. (explanation)
  5. Identify position of tendons and associated bursae beneath the palmar carpal ligament. (explanation)
  6. Identify the prominent features of carpals, metacarpals and phalanges associated with the hand as listed in the lab manual. (explanation)
  7. Define the thenar, hypothenar, central, and adductor-interosseous compartments of the hand and the functional significance of each. (explanation)
  8. Correlate any fractures or deep cuts of the hand with functional disruptions of associated muscular and neurovascular structures. (explanation)
  9. Describe the movements of the fingers and thumb. (explanation)
  10. Describe the collateral circulation of the hand. (explanation)

 

Learning Objectives and Explanations:

1. Identify the prominent features of the humerus, ulna, radius, carpals, metacarpals and phalanges of the associated extensor and flexor compartments as given in the lab manual. (W&B 127-129, 143-145, 154-156, N420N421N436N439N440N450N451N452N456TG2-04TG2-31TG2-32)

·       humerus: the bone of the upper arm. Its parts also serve as the origin for many muscles of the forearm. The medial epicondyle is the attachment site for the common flexor tendon, which gives rise to the superficial group of forearm flexor muscles (See #2 below). The lateral epicondyleis the attachment site for the common extensor tendon, which is the origin of some forearm extensor muscles (See #2 below). The lateral supracondylar ridge gives rise to thebrachioradialis muscle and the extensor carpi radialis longus muscle.

·       ulna: the medial bone of the forearm. It is more firmly connected to the humerus than the radius, but it is only indirectly articulated with the wrist and hand. Note that the head of the ulna is locateddistally. The tuberosity of the ulna is a point of insertion for the brachialis tendon along with thecoronoid process, which also forms part of the trochlear notch.

·       radius: the shorter, laterally-placed bone of the forearm. Its head is located on its smaller proximalend, and its lower end broadens to take almost the full contact of the bones of the wrist. Thetuberosity of the radius is the insertion point for the biceps brachii tendon. The interosseous crest is a point of attachment for the interosseous membrane, and the dorsal radial tubercleacts as a pulley point for the tendon of extensor pollicis longus, separating it from the tendons of the extensor carpi radialis longus and brevis muscles.

·       carpals: These eight small bones of the wrist are held together by ligaments and arranged in two rows, proximal and distal. The bones of the proximal row, listed from the radial to the ulnar side, are the scaphoid, the lunate, the triquetrum, and the pisiform. In the distal row, from radial to ulnar side, are the trapezium, the trapezoid, and capitate, and the hamate. Read across the proximal layer of bones: Send Louis TParis. Read across the distal layer of bones: TTame CarnalHunger. (Note that the pisiform bone is a sesamoid bone in the tendon of the flexor carpi ulnaris.)

·       metacarpals: There are five metacarpal bones, numbered from 1 (the thumb) to 5 (the little finger). These bones are just distal to the carpals.

·       phalanges: There are fourteen of these "bones of the fingers." The thumb has only two phalanges, a proximal and distal, where as the other digits each have three phalanges, proximal, middle, and distal.

2. Identify the extensor and flexor compartments of the forearm and hand, the nerve and vessels supplying their contents, and the functional significance of the included muscles. (W&B 135-143, N434N439N441,N444N445N446N447N448N449N450N451N452N454N456N459N460N461N462,N463N464N465N466N468N470N472AN472BN475N476N478N481TG2-23TG2-24,TG2-25TG2-26ATG2-26BTG2-27ATG2-27BTG2-28BTG2-28CTG2-29TG2-30)

The forearm is organized into anterior and posterior compartments separated by the interosseous membrane that connects the radius and ulna. The anterior compartment contains the flexor muscles, together with the median nerve (and branches), the ulnar nerve, and accompanying vessels. The posterior compartment contains the extensor muscles (with the exception of the brachioradialis, which is an elbow flexor), the radial nerve, and its branches. There are nineteen muscles in the forearm. Within both the posterior and anterior compartments there are two and three layers of muscle groups, respectively. A good way to memorize the muscles is by group level. The tables immediately below are listed according to that. Further below is a list of the muscles sorted by function.

superficial extensors:

Muscle

Origin

Insertion

Action

Innervation

Blood Supply

brachioradialis

upper two-thirds of the lateral supracondylar ridge of the humerus

lateral side of the base of the styloid process of the radius

flexes the elbow, assists in pronation & supination

radial nerve

radial recurrent a.

extensor carpi radialis longus

lower one-third of the lateral supracondylar ridge of the humerus

dorsum of the second metacarpal bone (base)

extends the wrist; abducts the hand

radial nerve

radial a.

extensor carpi radialis brevis

common extensor tendon (lateral epicondyle of humerus)

dorsum of the third metacarpal bone (base)

extends the wrist; abducts the hand

deep radial nerve

radial a.

 

extensor digitorum

common extensor tendon (lateral epicondyle of the humerus)

extensor expansion of digits 2-5

extends the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints of the 2nd-5th digits; extends wrist

deep radial nerve

interosseous recurrent a. and posterior interosseous a.

extensor digiti minimi

common extensor tendon (lateral epicondyle of the humerus)

joins the extensor digitorum tendon to the 5th digit and inserts into the extensor expansion

extends the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints of the 5th digit

deep radial nerve

interosseous recurrent a.

extensor carpi ulnaris

common extensor tendon & the middle one-half of the posterior border of the ulna

medial side of the base of the 5th metacarpal

extends the wrist; adducts the hand

deep radial nerve

ulnar a.


deep extensors:

Muscle

Origin

Insertion

Action

Innervation

Blood Supply

supinator

lateral epicondyle of the humerus, supinator crest & fossa of the ulna, radial collateral ligament, annular ligament

lateral side of proximal one-third of the radius

supinates the forearm

deep radial nerve

recurrent interosseous a.

abductor pollicis longus

middle one-third of the posterior surface of the radius, interosseous membrane, mid-portion of posterolateral ulna

radial side of the base of the first metacarpal

abducts the thumb at carpometacarpal joint

deep radial nerve

posterior interosseous a.

extensor pollicis brevis

interosseous membrane and the posterior surface of the distal radius

base of the proximal phalanx of the thumb

extends the thumb at the metacarpophalangeal joint

deep radial nerve

posterior interosseous a

extensor pollicis longus

interosseous membrane and middle part of the posterolateral surface of the ulna

base of the distal phalanx of the thumb

extends the thumb at the interphalangeal joint

deep radial nerve

posterior interosseous a

extensor indicis

interosseous membrane and the posterolateral surface of the distal ulna

its tendon joins the tendon of the extensor digitorum to the second digit; both tendons insert into the extensor expansion

extends the index finger at the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints

deep radial nerve

posterior interosseous a


superficial flexors:

Muscle

Origin

Insertion

Action

Innervation

Blood Supply

pronator teres

common flexor tendon and (deep or ulnar head) from medial side of coronoid process of the ulna

midpoint of the lateral side of the shaft of the radius

pronates the forearm

median nerve

ulnar a., anterior ulnar recurrent a.

flexor carpi radialis

common flexor tendon from the medial epicondyle of the humerus

base of the second and third metacarpals

flexes the wrist, abducts the hand

median nerve

ulnar a.

palmaris longus

common flexor tendon from the medial epicondyle of the humerus

distal half of flexor retinaculum and palmaris aponeurosis

flexes hand (at wrist) and tightens palmar aponeurosis

median nerve (C7 and C8)

ulnar a.

flexor carpi ulnaris

common flexor tendon & (ulnar head) from medial border of olecranon & upper 2/3 of the posterior border of the ulna

pisiform, hook of hamate, and base of 5th metacarpal

flexes wrist, adducts hand

ulnar nerve

ulnar a.

flexor digitorum superficialis

humeroulnar head: common flexor tendon; radial head: middle 1/3 of radius

shafts of the middle phalanges of digits 2-5

flexes the metacarpophalangeal and proximal interphalangeal joints

median nerve

ulnar a.


deep flexors:

Muscle

Origin

Insertion

Action

Innervation

Blood Supply

flexor digitorum profundus

posterior border of the ulna, proximal two-thirds of medial border of ulna, interosseous membrane

base of the distal phalanx of digits 2-5

flexes the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints

median nerve (radial one-half) via anterior interosseous n.; ulnar nerve (ulnar one-half)

ulnar a., anterior interosseous a.

flexor pollicis longus

anterior surface of radius and interosseous membrane

base of the distal phalanx of the thumb

flexes the metacarpophalangeal and interphalangeal joints of the thumb

median via anterior interosseous n.

anterior interosseous a.

 

pronator quadratus

medial side of the anterior surface of the distal one-fourth of the ulna

anterior surface of the distal one-fourth of the radius

pronates the forearm

median via anterior interosseous n.

anterior interosseous a.


Sorted by function:


flexor division:

·       muscles which rotate the radius on the ulna:

o      pronator teres (superficial group, anterior compartment - pronates)

o      pronator quadratus (deep group, anterior compartment - pronates)

o      supinator (deep group, posterior compartment - supinates)

·       muscles which flex the hand at the wrist:

o      flexor carpi radialis (superficial group, anterior compartment)

o      flexor carpi ulnaris (superficial group, anterior compartment)

o      palmaris longus (superficial group, anterior compartment)

·       muscles which flex the digits:

o      flexor digitorum superficialis (intermediate group, anterior compartment)

o      flexor digitorum profundus (deep group, anterior compartment)

o      flexor pollicis longus (deep group, anterior compartment)

o       

3. Correlate any fractures or deep cuts of the forearm or hand with functional disruptions of associated muscular or neurovascular structures. (N461,N466,N472,N475,N477,N478N481TG2-23TG2-24TG2-25TG2-26ATG2-26BTG2-27ATG2-27BTG2-28BTG2-28CTG2-29TG2-30)

·       The flexor digitorum superficialis has four tendons, which at the wrist lie in two layers. The tendons destined for the third and fourth fingers lie superficially in the compartment; the second and fifth digits are more deeply placed. As a result, a deep cut to the wrist would more likely leave the third and fourth flexor tendons injured. (Note that a cut to this part of the wrist, a frequently attempted spot for suicide, would be more likely to cause injury to cutaneous veins or flexor tendons 3 and 4 than to an artery. No major artery is located at this position.)

·       The radial nerve may be injured in its groove on the posterior aspect of the humerus. By this level the nerve has given off all its branches to the triceps muscle so there is no loss of extension at the elbow. However, all postaxial muscles (forearm extensors) below this level would be paralyzed, resulting in "wrist-drop" and the inability to extend the hand or digits. (The interphalangeal joints canstill be extended by the unaffected interosseus and lumbrical muscles.) There will be sensory loss in the areas served by the posterior antebrachial cutaneous and superficial radial nerves.

·       Injury to the median nerve at the wrist emphasizes the importance of opposition in the activities of the hand. Loss of the motor or recurrent branch of the median nerve paralyzes the muscles of the thenar eminence, with subsequent wasting of this area. The thumb can no longer be opposed to the other digits and the normal grasp of the hand is lost. There is also important sensory loss in the areas of distribution of the proper digital branches of the median nerve to the digits.

·       Injury to the ulnar nerve at the wrist produces a deformed "claw-hand". The thumb is strongly abducted and all the metacarpophalangeal joints are hyperextended. There is marked wasting through the hand, as well as sensory defects in the little finger and medial half of the ring finger.

4. Describe the movements of elbow, wrist, and finger joints. (N436,N439A,N439B,N453A,N453B,N453C,N458TG2-43ATG2-43BCTG2-44ATG2-44BTG2-44C,TG2-45ATG2-45B)

·       The wrist joint, also called the radiocarpal articulation, has great movement ability because of its convex oval articular surface. The joint can flex, extend, abduct, adduct and circumduct. Rotary motion is prohibited.

·       The "knuckles", or metacarpophalangeal joints (MP), are characterized by loose articular capsules. Movements of flexion and extension, abduction and adduction and circumduction are permitted at these joints. Extension is making a flat hand; flexion is making a fist. The metacarpophalangeal joint of the thumb is limited to the actions of flexion and extension. (The thumb's freedom of movement is a result of its carpometacarpal joint).

·       The elbow joint is essentially a hinge joint (ginglymus). However, the elbow joint also includes within a common articular capsule the proximal radioulnar joint, an articulation which is described with other radioulnar articulations. The movements of the elbow joint are flexion and extension. The freedom with which the hand can be elevated in flexion at the elbow is due to the slight medial rotation of the humerus and the semipronated position of the forearm, which is habitual. Flexion of the elbow joint is produced by the action of the biceps and brachialis muscles with the assistance of brachioradialis and those forearm muscles arising from the medial epicondyle (common flexor tendon). Extension of the elbow is due to the pull of the triceps and anconeus muscles. Please refer to Woodburne and Burkel pages 174-5 for good diagrams and a complete description of this joint.

5. Identify position of tendons and associated bursae beneath the extensor retinaculum and palmar carpal ligament. (W&B 149-154, N461N462N463,N470TG2-40ATG2-41ATG2-34B)

Images from "Anatomy of the Human Body" by Henry Gray are provided by:

 

Synovial sheaths, like bursae, reduce the frictional effects of the passage of the tendons through tight compartments of the wrist. A sheath is formed like a double-walled tube, the delicate inner wall closely attached to the tendon and its outer wall lining the compartment in which the tendon lies. The two layers are continuous with one another at the ends of the tube.

Each of the compartments on the dorsum of the wrist contains a synovial sheath investing the tendon(s) included in the compartment. The upper ends of the sheaths on the dorsum of the hand lie at the upper border of the extensor retinaculum, and they extend variable distances distal to it. They end just short of the inserting tendon (For example, the extensor carpi radialis longus and brevis, and the extensor carpi ulnaris sheaths end just short of their insertions on the bases of the metacarpal bones.)

On the palmar aspect of the wrist the tendons of the palmaris longus and flexor carpi ulnaris are not provided with synovial sheaths. The digital flexors, however, are protected at the wrist by complex synovial coverings: The radial bursa is a long synovial sheath for the tendon of flexor pollicis longus, which extends along this tendon from several centimeters above the flexor retinaculum to just proximal to its insertion on the distal phalanx of the thumb. The ulnar bursa is the complex covering of the digital flexor tendons. It occupies the center of the fibro-osseous tunnel of the wrist and also extends above the flexor retinaculum for several centimeters. This sheath exhibits the invaginated character of synovial sheaths. The general sheath for these eight tendons continues to about the middle of the palm and terminates there, except for the portion concerned with the fifth digit, which continues as far as the insertion of the profundus tendon on the base of the distal phalanx.

Cultural enrichment: Check out these sections from the 1918 version of Gray's Anatomy of the Human Body! Some of the terms are (of course) out-of-date, but the illustrations are timeless.

The Anterior Divisions (nerves) - The Veins of the Upper Extremity and Thorax - The Brachial ArteryThe Radial Artery - The Ulnar Artery - The Muscles and Fascia¾ of the Forearm - Surface Anatomy of the Upper Extremity - Surface Markings of the Upper Extremity

 

6. Identify the prominent features of carpals, metacarpals and phalanges associated with the hand as listed in the lab manual. (W&B 154-156, N452N456TG2-31TG2-32)

·       carpals: These eight small bones of the wrist are held together by ligaments and arranged in two (irregular) rows, proximal and distal. The bones of the proximal row, listed from the radial to the ulnar side, are the scaphoid, the lunate, the triquetrum, and the pisiform. In the distal row, from radial to ulnar side, are the trapezium, the trapezoid, the capitate, and the hamate. Read across the proximal layer of bones: Send Louis TParis. Read across the distal layer of bones: TTameCarnal Hunger, or the more racey: Some Lovers Try Positions That They Can't Handle. Can you guess which is the favorite of medical students? (Note that the pisiform bone is a sesamoid bone in the tendon of the flexor carpi ulnaris, so it sits on the volar surface of the triquetrum.)

·       metacarpals: There are five metacarpal bones, numbered from 1 (the thumb) to 5 (the little finger). These bones are just distal to the carpals.

·       phalanges: There are fourteen of these "bones of the fingers." The thumb has only two phalanges, a proximal and distal, whereas the other digits each have three phalanges, proximal, middle, and distal.

7. Define the thenar, hypothenar, central, and adductor-interosseous compartments of the hand and the functional significance of each. (W&B 158-169, N447N448N459N460N461N465N466N468,N472AN472BN459N460N462TG2-34ATG2-34BTG2-35ATG2-35BC)

The hand is entirely wrapped in fascia, with the palmar and dorsal fascia being continuous with one another on both sides. This fascia is relatively thin, except in a triangular area on the middle of the palm. Here the fascia, which is also connected to the flexor retinaculum and palmaris longus tendon (if present) is called the palmar aponeurosis. Furthermore, just like in the lower limb and in the arm and forearm, there are septa that further divide the space into compartments.

In the palm of the hand, there are three important septa. The lateral fibrous septum runs from the lateral part of the palmar aponeurosis to the deep aspect of the third metacarpal. This septum is the border between the thenar compartment lateral to it (towards the thumb) and the central compartment medial to it. Similarly, the medial fibrous septum runs from the medial aspect of the palmar aponeurosis to the deep part of the fifth metacarpal. It separates the hypothenar compartment, which is medial, towards the little finger, from the aforementioned central compartment. Finally, a septum runs medially from the medial side of the first metacarpal to the deep part of the third metacarpal. It separates the more superficial thenar compartment from the deeper adductor compartment.

The intrinsic muscles of the hand are listed below, divided by compartment.

thenar compartment:

Muscle

Origin

Insertion

Action

Innervation

Blood Supply

abductor pollicis brevis

flexor retinaculum, scaphoid, trapezium

base of the proximal phalanx of the first digit

abducts thumb

recurrent branch of median nerve

superficial palmar br. of the radial a.

flexor pollicis brevis

flexor retinaculum, trapezium

proximal phalanx of the 1st digit

flexes the carpometacarpal and metacarpophalangeal joints of the thumb

recurrent branch of the median nerve

superficial palmar br. of the radial a.

opponens pollicis

flexor retinaculum, trapezium

shaft of 1st metacarpal

opposes the thumb

recurrent branch of median nerve

superficial palmar br. of the radial a.


adductor/interosseous compartment:

Muscle

Origin

Insertion

Action

Innervation

Blood Supply

adductor pollicis

oblique head: capitate and base of the 2nd and 3rd metacarpals; transverse head: shaft of the 3rd metacarpal

base of the proximal phalanx of the thumb

adducts the thumb

ulnar nerve, deep branch

deep palmar arterial arch

dorsal interosseous (hand)

four muscles, each arising from two adjacent metacarpal shafts

base of the proximal phalanx and the extensor expansion on lateral side of the 2nd digit, lateral & medial sides of the 3rd digit, and medial side of the 4th digit

flex the metacarpophalangeal joint, extend the proximal and distal interphalangeal joints of digits 2-4, abduct digits 2-4 (abduction of digits in the hand is defined as movement away from the midline of the 3rd digit)

ulnar nerve, deep branch

dorsal and palmar metacarpal aa.

palmar interosseous

three muscles, arising from the palmar surface of the shafts of metacarpals 2, 4, & 5 (a palmar interosseous for the thumb is usually fused with the adductor pollicis m.)

base of the proximal phalanx and extensor expansion of the medial side of digit 2 and lateral side of digits 4 & 5

flexes the metacarpophalangeal, extends proximal and distal interphalangeal joints and adducts digits 2, 4, & 5 (adduction of the digits of the hand is in reference to the midline of the 3rd digit)

ulnar nerve, deep branch

palmar metacarpal aa.


hypothenar compartment:

Muscle

Origin

Insertion

Action

Innervation

Blood Supply

abductor digiti minimi (hand)

pisiform

base of the proximal phalanx of the 5th digit on its ulnar side

abducts the 5th digit

ulnar nerve, deep branch

ulnar a.

flexor digiti minimi brevis (hand)

hook of hamate & the flexor retinaculum

proximal phalanx of the 5th digit

flexes the carpometacarpal and metacarpophalangeal joints of the 5th digit

ulnar nerve, deep branch

ulnar a.

opponens digiti minimi

hook of hamate and flexor retinaculum

shaft of 5th metacarpal

opposes the 5th digit

ulnar nerve, deep branch

ulnar a.


central compartment:

Muscle

Origin

Insertion

Action

Innervation

Blood Supply

lumbrical (hand)

flexor digitorum profundus tendons of digits 2-5

extensor expansion on the radial side of the proximal phalanx of digits 2-5

flex the metacarpophalangeal joints, extend the proximal and distal interphalangeal joints of digits 2-5

median nerve(radial 2) via palmar digital nerves & ulnar nerve (ulnar 2) via deep branch

superficial palmar arterial arch

And finally, we have poor little palmaris brevis muscle. As if it isn't bad enough that the palmaris longus muscle is highly variable, its little brother, the palmaris brevis muscle, is thin, largely insignificant mechanically, and is superficial to, not in, the hypothenar compartment. It does serve to protect the ulnar nerve and artery, which it does valiantly, as well as give you that funny little skin pucker when you make a tight fist.

Muscle

Origin

Insertion

Action

Innervation

Blood Supply

palmaris brevis

fascia overlying the hypothenar eminence

skin of the palm near the ulnar border of the hand

draws the skin of the ulnar side of the hand toward the center of the palm

superficial br. of theulnar n.

ulnar a.

To summarize innervation, there are two main nerves. The median nerve gets the thenar muscles via its recurrent (motor) branch, as well as half of the lumbricals. The deep branch of the ulnar nerve gets all of the rest, with the exception of the palmaris brevis muscle, which is innervated by a superficial branch of the ulnar nerve.

8. Correlate any fractures or deep cuts of the hand with functional disruptions of associated muscular and neurovascular structures.

The two classic examples here both involve the median nerve:

Injury to the median nerve at the wrist, in, say, a case of carpal tunnel syndrome, results in severe paralysis of some hand motions and loss of cutaneous sensation. Most noticeable is the loss of the ability to oppose the thumb, since the only muscle that does this for the thumb is an intrinsic hand muscle innervated by the median nerve, the opponens pollicis muscle. (Other intrinsic muscles of the hand can call for back-up from forearm muscles, to, for example, flex the thumb or little finger. These actions will, of course, be weakened somewhat.)(Hint: Know about carpal tunnel syndrome.)

Often, farm equipment, switchblades, or broken glass can produce a direct wound to the thenar eminence, possibly injuring the recurrent (motor) branch of the median nerve itself. This also paralyzes the muscles of the thenar eminence, and causes subsequent wasting of the area. But, depending on what branches had already been given off, the lesion may be less severe than one caused farther up the chain at the wrist.

Other injuries are of course possible. Use your imagination to figure out what things one could cut when falling with arms outstretched through a plate-glass window, then use the tables to figure out how that person would present to you in the Emergency Department.

9. Describe the movements of the fingers and thumb. (W&B 13-14, N463N464N465TG2-45TG2-24)

The flexion and extension of the fingers is pretty straightforward. Abduction andadduction of them is the same as with the toes, with the third digit (2nd finger, "middle" finger) held as the axial line. The other three fingers either move toward (adduction) or away from (abduction) this finger.

The thumb gets to be a little tricky. Opposition is where you bring the pad of the thumb into contact with the pad of another digit, often specifically the little finger. This "simple" motion, which sets us apart from all but our closest monkey cousins, is really quite complex. But, the rest of the "standard" motions of the thumb are defined differently than for the other digits.Abduction is bringing the thumb out, away from the plane of the palm. Make a hand puppet, then straighten your MP joints. Your thumb is abducted. Clearly, bringing it back, then, is adductionExtension of the thumb takes place as you move it away from the other digitswithin the plane of the palm, like when hitchhiking or making the "L for loser" sign on your forehead. Flexion is not only bringing it back, but then further moving it such that it is lying across the palm.

10. Describe the collateral circulation of the hand. (W&B 185, N466N469TG2-37ATG2-37B)

There are a bunch of places in the hand where arterial anastomosis occurs:

·       both the superficial and deep palmar arches get blood from both the radial and ulnar arteries

·       palmar metacarpal arteries with the common palmar digital arteries

·       the perforating branches of the dorsal metacarpals with both the deep palmar arch and the common palmar digital arteries

·       the proper dorsal arteries with the palmar digital arteries

Cultural enrichment: Check out these sections from the 1918 version of Gray's Anatomy of the Human Body! Some of the terms are (of course) out-of-date, but the illustrations are timeless.

The Anterior Divisions (nerves) - The Veins of the Upper Extremity and Thorax - The Brachial ArteryThe Radial Artery - The Ulnar Artery - The Muscles and Fascia of the Forearm - The Muscles and Fascia of the Hand - Surface Anatomy of the Upper Extremity - Surface Markings of the Upper Extremity

 

 

Questions and Answers:

11. After removing the posterior antebrachial fascia (leaving the extensor retinaculum intact), do you see intermuscular septa? If not, why?

The answer is no. At this distal part of the forearm, intermuscular septum would limit movement of the muscles contained.

12a. Carefully open a compartment and distinguish parietal and visceral layers. Where do they become continuous?

The parietal layer of a synovial sheath reflects onto the visceral layer (on the associated tendon) both proximally and distally to its passage, deep to a retinaculum. (N462TG2-40A,TG2-41A)

12b. How do bursae function?

Bursae and synovial sheaths are synovial bags containing synovial fluid, which gives these bags a lubricating quality, reducing the friction on tendons.

12c. What is the posterior interosseous nerve?

The posterior interosseous nerve is the sensory continuation of the deep radial nerve, distal to its motor branches to the extensor muscles. It reaches the wrist joint and carpal bones for proprioceptive sense from these structures. (N445,N478TG2-30)

13. Review the radius, ulna, and the general arrangement of carpals, metacarpals, and phalanges in an articulated hand.

See #1 above. (N436,N439,N452,N456TG2-04TG2-31TG2-32)

14. Note the differences between the palmar carpal ligament and the extensor retinaculum.

The extensor retinaculum extends from the lateral margin of the radius to the styloid process of the ulna, the pisiform bone, and the triquetrum. The retinaculum has deep attachments to the ridges on the dorsum of the distal end of the radius. The palmar carpal ligament is also a thickening of the antebrachial fascia, however, it is on the flexor side of the wrist. It is attached to the styloid processes of both radius and ulna and crosses the tendons of the superficial flexor muscles and the ulnar nerve and blood vessels. Deep to the palmar carpal ligament is the flexor retinaculum. (N459N460N461,N470TG2-29TG2-24)

15. What muscles lie within the fascial plane of the palmar carpal ligament?

The tendons of flexor carpi radialis, palmaris longus, and flexor carpi ulnaris muscles lie deep to the palmar carpal ligament at the wrist. However, these tendons lie superficial to the flexor retinaculum. (N461TG2-23TG2-24)

16a. What muscles lie deep to the fascial plane of the palmar carpal ligament?

Deep to the palmar carpal ligament is the flexor retinaculum, under which the tendons of the flexor pollicis longus, the flexor digitorum superficialis, and the flexor digitorum profundus muscles pass. Note that at the wrist, the tendons to digits three and four pass superficially to two and five from the flexor digitorum superficialis. (N461TG2-24)

16b. Where are the arteries, veins and nerves in relation to the fascial plane of the palmar carpal ligament?

The median nerve passes under the flexor retinaculum. It lies radial to the superficial row of flexor tendons. The ulnar nerve and artery lie within the palmar carpal ligament superficial to the flexor retinaculum. (N461TG2-24)

16c. With what is the palmar carpal ligament continuous distally?

The fascia of the palm of the hand is continuous with the anterior antebrachial fascia by way of the palmar carpal ligament of the wrist. (N459TG2-23)

17. Note the two heads of origin of the pronator teres muscle, and their relation to the median nerve. Which structures cross its insertion?

The pronator teres has both a humeral (superficial) and an ulnar (deep) head. The larger humeral head arises from the medial epicondyle of the humerus by means of the common flexor tendon and from the adjacent septa and fascia. The smaller ulnar head arises from the medial side of the coronoid process of the ulna and joins the deep aspect of the humeral head.Between these two heads of origin passes the median nerve, which innervates the pronator teres muscle.

The pronator teres muscle is directed obliquely across the forearm, and its tendon passes under the brachioradialis to insert on a rough impression on the shaft of the radius at the middle of its lateral surface opposite the supinator. The tendon is crossed by the superficial radial nerve and the radial vessels at its insertion. (
N447,N450,N475TG2-24)

18. Do you have a palmaris longus?

The palmaris longus, taking origin from the medial epicondyle, adjacent muscles, and antebrachial fascia, is one of the more variable muscles of the body, being absent in about 13% of cases. (N446TG2-23)

19. Do any structures lie between the first two layers of muscles, i.e., between the separate heads of pronator teres?

As answered above: Yes, the median nerve passes between the two heads of the pronator teres. (N447,N475TG2-24)

20. Note the fibrous arch spanning between the radius and the ulna. What passes beneath this arch? Trace three or four tendons as they pass beneath the palmar carpal ligament. What is their arrangement?

This fibrous arch serves as part of the origin of the flexor digitorum superficialis. The median nerve passes distally immediately deep to this arch, in contact with the deep fascia of flexor digitorum superficialis. The arrangement of the flexor digitorum superficialis tendons are described above. (N447,N461TG2-24)

21. From the cubital fossa trace the brachial artery distally as it divides into the radial and ulnar arteries. Where is the point of bifurcation? Define the course and relations of the radial artery.

The central structure in the cubital fossa is the tendon of the biceps brachii muscle. Medial to the tendon lies the brachial artery, which bifurcates into the radial and ulnar arteries opposite the neck of the radius, in the inferior portion of the fossa.

The radial artery, the smaller of the two branches, continues the direct line of the brachial trunk. The artery lies in the intermuscular cleft of the lateral side of the forearm. In the upper one-third of the forearm it runs between the brachioradialis and pronator teres muscles. In the lower part of the forearm the artery lies under the antebrachial fascia with the superficial radial nerve lateral to it. Its branches in the forearm are the radial recurrent, muscular, palmar carpal, and superficial palmar arteries. At the wrist, the radial artery marks the (manual) pulse point. It then continues to the extensor portion of the hand, and in its course lies deep within the anatomical snuffbox. (
N447,N466TG2-24TG2-26)

22a. Consider the collateral circulation of the elbow between branches of brachial, deep brachial, radial and ulnar arteries.

Like all moveable joints, there is ample collateral circulation around the elbow. The superior and inferior ulnar collateral branches of the brachial artery anastomose with the anterior and posterior ulnar recurrent branches of the ulnar artery. The middle collateral and radial collateral branches of the deep brachial artery anastomose with the radial recurrent branch of the radial artery and the interosseous recurrent branch of the posterior interosseous artery. (N434TG2-26TG2-19)

23. Where do muscular branches to the flexor muscles arise? Locate precisely at the wrist.

See #3 above. (N475N476TG2-24)

24. What muscles does the anterior interosseous nerve supply? Where does it arise? What are its relations?

The anterior interosseous nerve supplies the flexor pollicis longus, the radial half of the flexor digitorum profundus, and the pronator quadratus muscles. It arises from the back of the median nerve in the cubital fossa and passes directly along the anterior side of the interosseous membrane distally to the pronator quadratus. It then passes deep to this muscle to end in sensory twigs to the wrist joint. (N448TG2-25)

25. Locate the ulnar nerve at the wrist. Note its specific relations to flexor carpi ulnaris, to flexor digitorum superficialis and profundus, and to the ulnar artery. What muscles does it supply? Where do these branches leave the ulnar nerve?

At the wrist the ulnar nerve is immediately to the radial side of the pisiform bone.

At the elbow it passes between the humeral and ulnar heads of the flexor carpi ulnaris. In the upper part of the forearm, the ulnar nerve lies on flexor digitorum profundus and is covered by flexor carpi ulnaris. It lies deep to the flexor digitorum superficialis. Distally, the ulnar artery meets the nerve, and in the lower half of the forearm they lie side by side, the artery on the radial side of the nerve.

The muscular branches of the ulnar nerve supply the flexor carpi ulnaris and the ulnar portion (to digits 4 & 5) of the flexor digitorum profundus muscles.

The ulnar nerve, like the median nerve, has no branches in the arm. In the forearm it has articular, muscular, and cutaneous branches. The articular branches are distributed at the elbow joint. In the upper portion of the forearm the muscular branches diverge. In the lower half of the forearm two cutaneous branches are given off. The palmar branch arises from the ulnar nerve near the middle of the forearm and runs downward superficial to the artery. Along the radial aspect of the pisiform bone, the ulnar nerve divides into its terminal branches to the hand, the superficial and deep branches. (N447N448,N468,N472A,N476,N481TG2-24,TG2-25TG2-27)

26. Locate the palmar digital branches of the median and ulnar nerves along the borders of the digits. Determine area of distribution. Do they supply any portion of the dorsal side of the digit? How much? Significance? What do they accompany?

The proper palmar digital branches of median nerve reach the radial 3 and 1/2 digits, while the ulnar branches reach the remaining ulnar 1 and 1/2 digits. Each palmar digital branch sends branches onto the dorsal surface of the distal phalanx, to supply the nail bed. Proper palmar digital arteries, primarily from the superficial palmar arterial arch, travel with the nerves. (N468,N472ATG2-33BTG2-38A)

27. What is the relation of the palmar aponeurosis to palmaris longus tendon, the palmar carpal ligament, and the flexor retinaculum?

The palmaris longus tendon spreads to unite with the palmar aponeurosis. The tendon passes deep to the palmar carpal ligament, and superficial to the flexor retinaculum. (N459N460,N461TG2-23TG2-24)

28. Identify the superficial transverse metacarpal ligament and transverse fasciculi and note the gaps between them. What can be seen in these gaps?

The common palmar digital neurovascular bundles can be found dividing into their proper palmar digital branches in these gaps. (N459TG2-33)

29a. What is the carpal tunnel and its associated syndrome?

The anatomy tables cover it well. It says that carpal tunnel syndrome: "results from any lesion that significally reduces the size of the carpal tunnel. Fluid retention, infection, and excessive exercise of the fingers may cause swelling of the tendons or their synovial sheaths. Median nerve is the most sensitive structure in the carpal tunnel and therefore is the most affected. Median nerve has sensory branches to the lateral three and a half digits thus paresthesia (abnormal sensation), hypothesia (reduced sensation), or anesthesia (loss of sensation) may occur. Furthermore, the main motor branch of the median nerve is the recurrent branch which serves three thenar muscles (it also serves the radial 2 lumbricals via common palmar digitals). Continued compresion of the median nerve will lead to weakness of the abductor pollicis brevis and opponens pollicis. To relieve the symptoms, partial or complete surgical division of the flexor retinaculum (carpal tunnel release) may be necessary. Clinically this syndrome can be tested for by tapping on the carpal tunnel. If symptoms are elicited (positive Tinel's sign), the syndrome is likely." (N461,N472A,N475TG2-34ATG2-34BTG2-35)

30. What artery completes the superficial palmar arterial arch?

The superficial palmar branch of the radial artery completes the superficial palmar arterial arch. (N466TG2-37)

31a. How do median and ulnar nerves share in the cutaneous innervation of the digits (review)?

Median nerve branches reach the radial 3 1/2 digits, while ulnar branches reach the remaining ulnar 1 1/2 digits. This includes the dorsal surface of the distal phalanx, to supply the nail bed. (N472TG2-33TG2-38)

32. Does the flexor pollicis brevis muscle have a deep head?

Yes, the deep head arises from the trapezoid and capitate, while the superficial head arises from the flexor retinaculum and the trapezium. (N465TG2-34)

33. Trace the superficial palmar branch of the radial artery to the thenar compartment. Does it continue beyond the compartment? Where?

The superficial palmar branch of radial artery completes the superficial palmar arch by passing into the central compartment, deep to the palmar aponeurosis. (N466TG2-37ATG2-37B)

34. What is the source of innervation for the hypothenar muscles?

As discussed in #3 above, the deep branch of ulnar nerve innervates these muscles. It passes between the abductor digiti minimi and flexor digiti minimi brevis muscles. (N465,N476TG2-34ATG2-34B)

35. Examine the contents of the carpal tunnel. How is it formed?

The carpal tunnel is formed by the attachment of the flexor retinaculum to the trapezium and scaphoid laterally, and the hook of the hamate and the pisiform medially. (N461TG2-34)

36. Into which digital sheath does the ulnar bursa continue distally?

The ulnar bursa continues into the sheath for the little finger flexor tendons, which means that an infection of the little finger involving its flexor and synovial sheaths could lead to an infection within the carpal tunnel. (N464TG2-34)

37. What are vincula?

Vincula (mesotendons) are folds of synovial membrane containing neurovascular pedicles supplying the flexor tendons. They are located between the phalanges and the flexor tendons. (N464TG2-45)

38. Identify the lumbrical muscles, noting origin. Trace them to their immediate and functional insertion. What is the course of innervation?

The radial 2 lumbricals are innervated by the median nerve, via its palmar digital branches. The ulnar 2 lumbricals are innervated by the ulnar nerve. (N463N464,N475,N476TG2-34A,TG2-34B)

39. Locate the flexor carpi radialis tendon. Is it in the carpal tunnel? What happens to it?

The tendon of flexor carpi radialis traverses a split in the flexor retinaculum to insert on the bases of the second and third metacarpals. (N461TG2-36)

40. Consider the complete blood supply to the hand, including sources and arches . How do the dorsal and palmar proper digital arteries differ in their formation? What are perforating arteries? Where are they found? What is their function?

The superficial palmar arch is formed by the superficial branch of the ulnar artery and the superficial palmar branch of the radial artery. The deep palmar arch is primarily formed by the radial artery anastomosing with the deep branch of the ulnar artery. Dorsal carpal branches of radial and ulnar unite to form a dorsal carpal arch. This arch gives off dorsal metacarpal arteries which divide into the dorsal digital arteries. Palmar digital arteries are branches of common digital branches of the superficial arch. Perforating arteries connect the dorsal and palmar metacarpal arteries (from the deep arch) at the heads of the metacarpal bones. (N466,TG2-37ATG2-37B)