16 - Posterior Arm, Posterior Forearm and the Hand

Question 1

triceps brachii

Answer 1

• long, medial & lateral heads (long head originates from infraglenoid tubercle of scapula)
• inserts on olecranon process of ulna
• forearm extensor, long head (from infraglenoid tubercle) assists in extension and adduction of arm at the shoulder
• Blood supply comes from the profunda brachii artery (a branch off brachial), innervation is from the radial n.

Question 2

olecranon bursae

Answer 2

There are both SUBCUTANEOUS & SUBTENDINOUS OLECRANON BURSAE associated with the olecranon process of the humerus and the tendon of triceps brachii.
The subcutaneous olecranon bursa is a common site for bursitis, often resulting from a fall on the elbows.

Question 3

anatomical snuff box

Answer 3

Boundaries:
Anterior: abductor pollicis longus and extensor pollicis brevis Posterior: extensor pollicis longus
Floor: scaphoid & trapezium
Contents: radial artery & vein

Question 4

most frequently fractured carpal bone

Answer 4

• scaphoid
• Pain in the anatomical snuff box may indicate a fractured scaphoid
• fractured scaphoid may lacerate the overlying radial artery.

Question 5

extensor expansion

Answer 5

-flattened extensor tendons
-Each expansion forms a
“hood” that holds the extensor tendon in the middle of the metacarpophalangeal joint.
-Extending distally from the hood are:
1 central band that inserts on the middle phalanx
2 lateral bands that insert on the distal phalanx
-Some intrinsic muscles of the hand (lumbricals and interossei) insert on the extensor expansion.

Question 6

superficial fascia of the palm

Answer 6

• fat containing superficial vessels and cutaneous nerves.

- contains the small Palmaris Brevis Muscle

Question 7

deep fascia of the palm

Answer 7

-It has a central thickening, the palmar aponeurosis

Question 8

palmar aponeurosis

Answer 8

• proximally continuous with flexor retinaculum ( and tendon of palmaris longus m. if there)
• divides into five bands that are continuous with fibrous digital sheaths
• fibrous intermuscular septa create compartments of the palm.

Question 9

thenar muscles (and innervation)

Answer 9

The thenar muscles (flexor pollicis brevis, abductor pollicis brevis and opponens pollicis) are supplied by the recurrent branch of the median nerve.

Question 10

innervation of adductor pollicis

Answer 10

Adductor pollicis is innervated by the ULNAR nerve

Question 11

lumbricals

attachements, actions, innervation

Answer 11

Attachments:
Originate on the tendons of FDP, insert onto the extensor expansion
Actions:
Flex the digits at the
metacarpophalangeal (MP) joint and extend the interphalangeal (IP) joints
Innervation:
Median nerve (1st and 2nd) Ulnar nerve (3rd and 4th)

Question 12

innervation of interossei

Answer 12

ulnar nerve

Question 13

actions of lumbricals and interosseous muscles

Answer 13

• tendons of the lumbricals and interossei muscles pass ventral to metacarpophalangeal joint to insert on lateral bands of the extensor expansions of the medial four digits.
• their line of pull is ventral to MP joints, but dorsal to the PIP and DIP joints.
• these muscles can all assist in flexion of the MP joints and extension of the DIP and PIP joints

Question 14

bifurcation of brachial artery

Answer 14

happens at level of radial head as it passes through cubital fossa
bifurcates into terminal branches (radial and ulnar a)

Question 15

ulnar artery

Answer 15

• moves medially to travel with the ulnar nerve.
• Travels with the ulnar nerve lateral to the tendon of the flexor carpi ulnaris.
• It’s pulse can be felt just proximal to the pisiform as it starts to pass superficial to the flexor retinaculum to reach the palmar surface of the hand.
• The ulnar artery is the main contributor to the superficial palmar arterial arch
• Other branches:
• Common interosseous artery divides into:
• anterior interosseous artery (to deep anterior forearm)
• posterior interosseous artery(to posterior forearm
• Deep palmar branch (to deep palmar arterial arch)

Question 16

radial artery

Answer 16

• Travels the length of the forearm just medial to the brachioradialis muscle.
• At the wrist it comes to lie on the anterior surface of the radius (take
  pulse here) before coursing onto the dorsum of the hand where it travels through the anatomical snuff box on the dorsum of the scaphoid bone.
• The radial artery then passes through the two heads of the 1st dorsal interosseous m. to reach the palmar surface where it becomes the primary contributor to the deep palmar arterial arch.
  -Other Branches:
  -Superficial palmar branch (to superficial palmar arterial arch)

Question 17

radial nerve

Answer 17

• terminal branch off the posterior cord of the brachial plexus.
• It and its branches innervate all muscles in posterior compartments of the upper limb
• enters the posterior aspect of the arm by passing through the triangular interval with the profunda brachii vessels (deep artery & vein of the arm). (neurovascular bundle lies directly on the humeral shaft (in the radial groove of the humerus) and spirals around the bone to reach the groove between brachialis and brachioradialis where it will divide into deep (motor) and superficial (cutaneous) radial nerves.)

Question 18

deep radial nerve

Answer 18

deep radial nerve pierces supinator m. and emerges from it’s distal edge as the posterior interosseous n. This nerve travels between superficial and deep layers of the posterior forearm and supplies most of the muscles in the compartment.

Question 19

superficial radial nerve

Answer 19

Superficial radial nerve supplies skin on the lateral side of the dorsum of the hand, and a small portion of the thenar eminence. The radial nerve supplies NO MUSCLES in the hand

Question 20

consequences of fracture of mid-humeral shaft

Answer 20

-injure the radial nerve. The patient will present with:
-loss of innervation to part of triceps; at least the long head of triceps will be spared and extension of the elbow will be weakened – not lost.
- all distal posterior muscles will be paralysed and extension of the wrist will become impossible resulting in a clinical condition called ‘wrist-drop’.
- there will also be loss of sensation to
regions below the elbow that are supplied
by branches of the radial nerve.

Question 21

median nerve

Answer 21

• The median nerve enters the palm of the hand through the carpal tunnel
• Once in the palm, it gives off:
• the recurrent branch of the median n. supplies the muscles of the thenar eminence (although the deep part of flexor pollicis brevis gets innervation from the deep ulnar n.)
• branches to the first two lumbricals
• cutaneous branches to the skin on the palmar surfaces of the of the first 31⁄2 digits

Question 22

low injury to median nerve

Answer 22

• usually at the wrist as a result of ‘carpal tunnel syndrome’
• the patient will have:
• loss of sensation to palmar surfaces of lateral 31⁄2 digits and the dorsal surfaces of their distal segments
• Loss of thumb opposition
• Ape Hand:
• thumb is rotated, & adducted (thumb is in same plane as other digits)
• Flattened (wasted) thenar eminence

Question 23

high injury to median nerve

Answer 23

• occurs at elbow/usually in cubital fossa
• The patient will present with the same symptoms as carpal tunnel syndrome. However, because of the more proximal lesion, there will be more paralysis.
• still has an ape hand, but the thumb is now extended (additional loss of FPL)
• Wrist flexion is accompanied by adduction
• When the person attempts to make a fist the first, second and third fingers will remain partially extended resulting in the HAND OF BENEDICTION

Question 24

ulnar nerve

Answer 24

• The ulnar nerve enters the palm of the hand through the ulnar canal (just lateral to the pisiform bone)
• In the palm of the hand, the ulnar nerve innervates all the intrinsic muscles of the hand not innervated by the median nerve. It’s Superficial branch is cutaneous to the palmar surfaces of the medial 11⁄2 digits.
• How will a person present if they have a high or low injury to the Ulnar n.?

Question 25

major branches of brachial plexus

Answer 25

• musculocutaneous nerve
• radial nerve
• median nerve
• ulnar nerve

Question 26

musculocutanous nerve

Answer 26

one of two terminal branches of the lateral cord of the brachial plexus, it pierces the coracobrachialis muscle and then continues distally in the plane between biceps brachii and brachialis muscles. It innervates all of the muscles in the anterior compartment of the arm, then emerges lateral to the biceps brachii muscle as the lateral cutaneous nerve of the forearm (a.k.a. lateral antebrachial cutaneous n.)

Question 27

radial nerve

Answer 27

terminal branch off the posterior cord of the brachial plexus. It and its branches innervate all muscles in the posterior compartments of the upper limb. It enters the posterior aspect of the arm by passing through the triangular interval (inferior to teres major; lateral to the long head of triceps) with the profunda brachii vessels (deep artery & vein of the arm). This neurovascular bundle lies directly on the humeral shaft (in the radial/ spiral groove of the humerus) and spirals around the bone to reach the groove between brachialis and brachioradialis where it will divide into deep (motor) and superficial (cutaneous) radial nerves. The deep radial nerve pierces supinator m. and emerges from it’s distal edge as the posterior interosseous n. This nerve travels between superficial and deep layers of the posterior forearm and supplies most of the muscles in the compartment.

Question 28

median nerve

Answer 28

arises from the brachial plexus by contributions from both the lateral and medial cords. It travels through the arm with the brachial artery and enters the cubital fossa. It travels in the forearm between intermediate and deep muscle layers. It innervates all superficial and intermediate muscles of the anterior compartment of the forearm except for flexor carpi ulnaris. It’s branch, the anterior interosseous nerve supplies all the deep muscles of the forearm except for the ulnar half of the flexor digitorum profundus muscle. It gives off a palmar cutaneous n. (to skin of the central palm) before travelling through the carpal tunnel on its way to innervate more muscles in the hand

Question 29

median nerve in palm

Answer 29

Once in the palm, it gives off:

• the recurrent branch of the median n. supplies the muscles of the thenar eminence (although the deep part of flexor pollicis brevis gets innervation from the deep ulnar n.)
• branches to the first two lumbricals
• cutaneous branches to the skin on the palmar surfaces of the of the first 31⁄2 digits

Question 30

ulnar nerve

Answer 30

terminal branch of the medial cord of the brachial plexus. It passes posterior to the medial epicondyle of the humerus (funny bone) and enters the forearm by passing through the cubital tunnel between the two heads of the flexor carpi ulnaris muscle (which it supplies). While in the forearm it gives off branches to FCU and ulnar half of FDP as well as Cutaneous branches to the hand. It enters the hand, with the ulnar vessels, by passing superficial to the flexor retinaculum in the ulnar canal (a.k.a., guyon’s canal – lateral to the pisiform). In the palm of the hand, the ulnar nerve innervates all the intrinsic muscles of the hand not innervated by the median nerve. It’s Superficial branch is cutaneous to the palmar surfaces of the medial 11⁄2 digits.

Question 31

long thoracic n

Answer 31

(C5-C7) innervates serratus anterior Trapezius is innervated by the spinal accessory n. (CN XI) Rotator cuff muscles – C5,C6
Intrinsic hand muscles – C8,T1

Question 32

role of dorsal rami in brachial plexus

Answer 32

DO NOT CONTRIBUTE!!

Question 33

axillary artery

Answer 33

short vessel that begins at the lateral border of the first rib as a distal continuation of the subclavian artery. It ends at the inferior border of the teres major muscle where it changes its name to the Brachial artery. It is surrounded by the cords and branches of the brachial plexus.

• The axillary vein lies on the medial/anterior side of axillary artery. It begins at the inferior border of teres major by the union of the brachial veins and the basilic vein and ends at the lateral border of the first rib where it becomes the subclavian vein.
• The proximal parts of the axillary vessels and the surrounding brachial plexus are enclosed in the axillary sheath (a distal continuation of the prevertebral fascia in the neck).
• For descriptive purposes, the axillary artery is divided into three parts by the presence of the pectoralis minor muscle. The part number also indicates its number of branches.

Question 34

brachial artery

Answer 34

supplies all of the blood to structures in the anterior compartment of the arm. It begins at the inferior border of the teres major muscle as a distal continuation of the axillary artery. It travels through the anterior arm with the median nerve and gives off:

• Branches to the humerus and structures in the anterior arm
• Deep artery of the arm (Profunda brachii artery) that travels to the posterior compartment of the arm with the radial nerve. -Collateral branches to the anastomosis around the elbow
• The brachial artery continues distally, it travels through the cubital fossa and terminates at the level of the radial head by bifurcating into the radial artery and the ulnar artery.

Question 35

ulnar artery

Answer 35

gives off the common interosseous a., which splits into the anterior and posterior interosseous aa. The posterior interosseous artery is the primary source of blood to the posterior compartment of the forearm. The ulnar artery then moves
medially to travel with the ulnar nerve. At the wrist, it is located lateral to the tendon of the flexor carpi ulnaris, where pulse can be felt, then runs superficial to the flexor retinaculum, in the ulnar canal just lateral to the pisiform bone, to reach the palmar surface of the hand. In the palm, it gives off the deep palmar branch (to the deep palmar arterial arch) and continues onto the palm as the superficial palmar arterial arch (an anastomosis between the ulnar a. and the superficial palmar branch of the radial a.)

Question 36

radial artery

Answer 36

travels the length of the forearm just medial to the brachioradialis muscle. At the wrist it comes to lie on the anterior surface of the radius (take pulse here) and gives off a superficial palmar branch which completes the superficial palmar arterial arch. The radial artery then courses posteriorly, traveling in the floor of the anatomical snuffbox, on the dorsum of the scaphoid bone. It then pierces the first dorsal interosseus muscle to enter the palm. When in the palm, the radial artery is the primary source of blood to the deep palmar arterial arch (completed by the the deep palmar branch of the ulnar artery).

Question 37

axillary artery boundaries

Answer 37

Begins at lateral border of 1st rib as a distal continuation of the Subclavian
artery. It supplies structures of the shoulder region

Question 38

brachial artery boundaries and functions

Answer 38

• Begins at inferior border of teres major as a distal continuation of the axillary artery - supplies structures of the arm -ends at elbow by bifurcating into radial and ulnar arteries

Question 39

radial artery boundaries

Answer 39

(to anterior & posterior forearm, dorsum of hand and palm)

Question 40

superficial palmart arterial arch

Answer 40

(blood primarily from ulnar a. to palm)

Question 41

subclavian artery boundaries

Answer 41

• right is a terminal branch off the brachiocephalic a., left is a direct branch off the aortic arch. Ends at the lateral border of the 1st rib

Question 42

profunda brachii boundaries

Answer 42

(a.k.a. deep artery of the arm, branch off brachial a. to the posterior compartment of the arm. Travels in the spiral groove of the humerus with the radial n.)

Question 43

ulnar artery boundaries

Answer 43

to anterior forearm and palm

Question 44

posterior interosseous

Answer 44

to posterior forarm

Question 45

deep palmar arterial arch

Answer 45

blood primarily from radial a to palm