FOREARM FLEXORS AND PALM OF HAND
I. FOREARM (ANTEBRACHIUM)
A. Extends from elbow to wrist
B. Contains two bones (radius and ulna)
C. Muscles: Flexors (anterior), extensors (posterior)
D. Compartments and fascia
1. Separated into anterior and posterior compartments by interosseus membrane
2. Antebrachial fascia continuous with brachial fascia - forms intermuscular septum medially
3. Lateral intermuscular septum - from radius to antebrachial fascia
E. Landmarks
1. Radius
2. Ulna
3. Distal humerus
F. Superficial structures - discussed previously
G. Muscles of forearm and their actions
1. 19 muscles (8 flexors)
2. Divided into functional groups of three (except brachioradialis)
3. Function to move hand and digits
4. Morphological and functional balance between flexors and extensors
H. Flexor muscles
1. Superficial group
- from radial to ulnar side - common tendinous origin from medial epicondyle of humerus - also flexes arm at elbow
a. Pronator teres
i. Attachments:
(a). Humeral head: medial epicondyle
(b). Ulnar head: medial coronoid process
(c). Distal: middle lateral radius
ii. Nerve: median (passes between heads)
iii. Artery: anterior ulnar recurrent
iv. Action: pronates and flexes forearm
b. Flexor carpi radialis
i. Attachments: medial epicondyle to base 2nd and 3rd metacarpals
ii. Nerve: median
iii. Artery: radial (posterior interosseus distally)
iv. Action: flex wrist, pronate and abduct hand, flex forearm
c. Palmaris longus - may be missing most of muscle belly (10-15%)
i. Attachments: medial epicondyle to transverse carpal ligament and palmar aponeurosis
ii. Nerve: median
iii. Artery: posterior ulnar recurrent
iv. Action: flex wrist, pronates and flexes forearm
d. Flexor carpi ulnaris
i. Attachments:
(a). Humeral head: medial epicondyle
(b). Ulnar head: olecranon
(c). Distal: pisiform, hamate, 5th metacarpal
ii. Nerve: ulnar (passes between two heads)
iii. Artery: posterior ulnar recurrent
iv. Action: flex wrist and forearm
2. Intermediate Layer
a. Flexor digitorum superficialis
i. Attachments:
(a). Humeral head: medial epicondyle
(b). Ulnar head: coronoid process
(c). Radial head: oblique line of radius
(d). Distal: palmar surface of middle phalanx of medial 4 digits (D2-5)
ii. Nerve: median
iii. Artery: ulnar and radial
iv. Action: flex middle and proximal phalanges, aids flexion of forearm
3. Deep group of muscles
- origin from ulnar and/or radius, interosseus membrane
a. Flexor digitorum profundus
i. Attachments: medial/anterior ulna to distal phalanges of D2-5
ii. Nerve: medial-ulnar, lateral-interosseus of median
iii. Artery: ulnar
iv. Action: flex terminal phalanges of D2-5, flex wrist
b. Flexor pollicus longus
i. Attachments: radius, coronoid process of ulna to distal phalanx D1 (palmar side)
ii. Nerve: median
iii. Artery: ulnar
iv. Action: flex thumb
c. Pronator quadratus
i. Attachments: distal ulna to lateral radius
ii. Nerve: median
iii. Artery: ulnar
iv. Action: pronates forearm
I. Nerves of forearm flexors
1. Ulnar nerve: supplies flexor carpi ulnaris and ulnar portion of flexor digitorum profundus
a. passes behind medial epicondyle of humerus then between heads of flexor carpi ulnaris
b. courses with ulnar artery in distal forearm
c. Branches
i. Muscular
ii. Superficial: sensory to wrist
2. Median nerve:
a. leaves cubital fossa between 2 heads of pronator teres
b. lies deep to flexor digitorum superficialis
c. Branches
i. Muscular – to flexors except FCU
ii. Articular - elbow joint
iii. Anterior interosseus
iv. Palmar cutaneous br.
J. Arteries in forearm
1. Radial artery - begins in cubital fossa opposite neck of radius - smaller branch
a. Muscular branches - lateral forearm
b. Radial recurrent artery - anastomoses with radial collateral artery
c. Superficial palmar branch
d. Palmar carpal
e. Dorsal carpal
2. Ulnar artery
a. Anterior ulnar recurrent
i. anastomoses with anterior br. of superior and inferior ulnar collateral aa. - from brachial a. superiorly
b. Posterior ulnar recurrent
i. anastomoses with posterior br. of superior and inferior ulnar collateral aa.
c. Common interosseus
i. anterior interosseus - becomes part of palmar carpal network distally
ii. posterior interosseus
(a). interosseus recurrent artery - anastomoses with br. of profunda brachii a.
(b). dorsal carpal artery
d. Muscular branches
e. Palmar carpal
f. Dorsal carpal
g. Superficial br.
h. Deep palmar br.
K. Veins - follow arteries
L. Lymphatics - continuous with brachial lymph trunks
III. WRIST AND PALM OF HAND
A. WRIST
1. movement of hand occurs here
2. 8 carpal bones
- arranged in two rows
a. proximal row
i. scaphoid
ii. lunate
iii. triquetrum
iv. pisiform (a sesamoid bone - articulates only with triquetrum)
b. distal row
i. trapezium
ii. trapezoid
iii. capitate
iv. hamate (with hamular process) = "hook"
3. Compartments and deep fascia
a. extensor retinaculum - thickened antebrachial fascia on dorsum of wrist
b. palmar carpal ligament - antebrachial fascia on palmar part of wrist - attaches to styloid process of radius and ulna
c. flexor retinaculum - deep to palmar ligament
i. attached to scaphoid and trapezium (laterally), pisiform and hook of hamate (medially)
ii. forms carpal tunnel for passage of vessels and nerves
(a). median nerve
(b). tendons of flex. dig. superficialis & profundus synovial sheaths
(c). Tendon of FPL m.
iii. carpal tunnel syndrome – see Clinical Considerations / assigned Blue Boxes section for lecture
4. Nerves and blood vessels
- important relationships
a. Ulnar nerve and artery: superficial to flexor retinaculum
b. Median nerve: under flexor retinaculum
c. Radial artery: occupies floor of "anatomical snuff box"
B. PALM OF HAND (Volar Surface)
1. Superficial structures
a. Thick skin, rich with sweat glands
b. Flexion creases - acquired - indicate anatomical landmarks
c. Cutaneous nerves
i. palmar cutaneous nerves (median and ulnar)
ii. lateral antebrachial cutaneous - from musculocutaneous n.
iii. superficial radial nerve
iv. digital nerves
2. Compartments and fascia
a. deep fascia continuous with antebrachial fascia
b. hypothenar fascia - invests muscles, nerves and vessels of little finger
c. thenar fascia - thumb
d. palmar aponeurosis
i. continuous with flexor retinaculum & tendon of palmaris longus m.
ii. divides into digital bands distally
e. fascial compartments
i. formed by septa connecting aponeurosis with underlying metacarpal bones
ii. hypothenar compartment - contains 3 muscles of little finger
iii. thenar compartment - contains thenar mm. of thumb
iv. central compartment - contains flexor tendons and sheaths, vessels and nerves
3. 5 metacarpal bones
4. 14 phalanges (2 in thumb) - proximal, middle and distal
C. Intrinsic muscles of the hand
1. 3 groups (compartments) - innervated by ulnar or median nerves (preaxial)
2. originate from flexor retinaculum and associated attachments
3. Thenar compartment - 3 short muscles produce thenar eminence - opposition - supplied by median nerve and superficial radial artery
a. Abductor pollicus brevis
i. Attachments: trapezium and scaphoid to proximal phalanx of thumb
ii. Nerve: median
iii. Artery: superficial radial
iv. Action: abducts thumb
b. Flexor pollicus brevis
i. Attachments: carpal lig and trapezium (two heads) to proximal phalanx of thumb
ii. Nerve: median
iii. Artery: superficialis radial
iv. Action: flexes proximal phalanx
c. Opponens pollicus - deep to abd. poll. brevis and flexor
i. Attachments: carpal lig and trapezium to 1st metacarpal
ii. Nerve: median
iii. Artery: radial
iv. Action: opposition
d. Adductor pollicis
i. Attachments:
(a). Oblique head: trapezium, trapezoid, capitate, base 2nd, 3rd metacarpals
(b). Transverse head: 3rd metacarpal
(c). Distal: proximal phalanx of thumb
ii. Nerve: ulnar
iii. Artery: deep arch
iv. Action: adducts thumb, aids opposition
4. Hypothenar compartment - 3 muscles - innervated by ulnar nerve
a. Abductor digiti minimi
i. Attachments: pisiform, tendon flexor carpi ulnaris to medial proximal phalanx of D5
ii. Nerve: ulnar
iii. Artery: deep arch - br. of ulnar
iv. Action: abducts little finger
b. Flexor digiti minimi brevis
i. Attachments: carpal ligament, hamulus to proximal phalanx D5
ii. Nerve: ulnar
iii. Artery: deep arch
iv. Action: flex proximal phalanx of little finger
c. Opponens digiti minimi - deep to abd. dig. minimi
i. Attachments: carpal ligament, hamulus to 5th metacarpal
ii. Nerve: ulnar
iii. Artery: deep arch
iv. Action: draws 5th metacarpal toward thumb
5. Interossei-adductor compartment
a. Palmar Interossei muscles (3) (PAD = Palmar ADuct)
i. Attachments: palmar surface of metacarpals 2, 4, 5 to extensor expansions and base proximal phalanges 2,4,5
ii. Nerve: ulnar
iii. Artery: digital arteries
iv. Action: adduct digits
b. palmar interosseus fascia
c. Adductor pollicis muscle
d. deep palmar arterial arch
e. deep branch of ulnar nerve
6. Central compartment
a. underlies palmar aponeurosis
b. contents
i. superficial palmar arterial arch
ii. median nerve
iii. ulnar nerve
iv. flexor tendons and sheaths - invested by ulnar bursa
c. Lumbrical muscles - 4 small muscles associated with flexor digitorum profundus
i. Attachments: tendons of flexor digitorum profundus to lateral (radial) side of proximal phalanx D2-5 (attach to extensor mechanism instead of bone)
ii. Nerve: median (1 &2) and ulnar (3 & 4)
iii. Artery: digital arteries
iv. Action: flex digits at MP joint, extend interphalangeal (IP) joints
D. Synovial sheaths
1. reduce friction of tendons through compartments or over bone
2. double walled tube, continuous at ends
3. contain synovial fluid
4. radial bursa - covering radial side of tendons
5. ulnar bursa - covering of distal flexor tendons
6. Important clinical presentations - infection, adhesions, compression
E. Nerves of the hand
1. Median nerve
a. enters in carpal tunnel
b. recurrent br. supplies 3 thenar muscles and 1st and 2nd lumbricals, part of add. pollicis
c. cutaneous innervation of lateral palmar surface, 3 1/2 digits (D1-4)
2. Ulnar nerve - nerve of fine movements
a. passes on flexor retinaculum, lateral to pisiform bone
b. palmar cutaneous branch - supplies medial palm
c. dorsal cutaneous branch
d. superficial branch - supplies medial 1 1/2 digits (D4-5)
e. deep branch - supplies hypothenar muscles, medial lumbricals (3 & 4), adductor pollicis and interossei mm.
3. Radial nerve
a. supplies NO intrinsic hand muscles
F. Arteries of hand
1. Radial artery
a. superficial palmar arch
b. princeps pollicis artery - thumb
c. deep palmar arterial arch - mainly radial, w/ small ulnar component
d. palmar metacarpal arteries
2. Ulnar artery
a. deep palmar branch
b. superficial palmar arch - mainly ulnar, small radial component
G. Veins of hand
1. Venae comitantes
2. Dorsal venous network >> cephalic vein