• 1. dorsum:
– a. knuckles = metacarpal bone heads
– b. skin - thinner than palm, has hair follicles, sebaceous & sweat glands
– c. dorsal venous network

• palm:
– a. skin - much thicker than dorsum, many sweat glands, no hair follicles or sebaceous
– b. transverse flexion creases: when metacarpophalangeal joints flex - proximal, distal
– c. longitudinal flexion creases - when thumb is opposed - radial & midpalmar
– d. thenar eminence - ball / heel of thumb
– e. hypothenar eminence - heel of hand at little finger

Trisomy 21

• Also have digital transverse flexion creases proximal, middle, distal (thumb has only 2)
• Fingerprints - improve gripping ability
• Synovial sheaths
– a. radial bursa - encloses tendon of flexor pollicis longus
– b. ulnar bursa - encloses four tendons each of flexors digitorum superficialis & profundus
& medially, extends distally to surround the two flexor tendons to pinkie
– c. Three separate distal sheaths - surround flexor tendons to index, middle, ring fingers
- from metacarpophalangeal joints to base of distal phalanx

• Fibrous digital sheaths - dense fibrous connective tissue
– annular bands - surround phalanges
– cruciform bands - cross over between joints
– form osteofibrous canals - through which flexor tendons travel (in their synovial sheaths)
• Flexor retinaculum
– Fibrous connective fascia that covers and holds most of the flexors of the forearm in wrist.

• Because the median is enclosed with the tendons in this tunnel, anything that decrease the size of the tunnel (infection, arthritis, degeneration etc.) will compress the median nerve causing carpal tunnel syndrome. Its symptom includes tingling sensation
(paresthenia), absence of tactile sensation
(anethesia), or diminished sensation
(hypothenia), loss strength of thumb (abductor pollicis brevis, flexor pollicis brevis and opponents pollicis), lumbricals (lateral two) can also be affected.

• Ulnar artery
– a. deep branch - joins radial to form deep palmar arch
– b. superficial palmar arterial arch, formed by superficial palmar branch from ulnar artery (more like the terminal branch of ulnar, which mainly forms the arch) + superficial palmar branch of radial artery. It gives off three branches and joint with palmar metacarpal branches from deep palmar arch to form:
• i) three common palmar digital artery - in the three medial intermetacarpal spaces; each then divides
• proper palmar digital artery - to medial side of index finger, radial side of little finger and both sides of middle & ring fingers
• proper palmar digital artery - little finger, ulnar side, a branch directly from the superficial palmar arch (or a branch off the ulnar artery)

• radial a. - (sits in floor of anatomical snuff box)
– a. superficial palmar branch - to thenar muscles, joins superficial palmar arch (ulnar)
– b. princeps pollicis - to thumb, then splits into two proper digital arteries to both sides of the thumb
– c. radialis indicis - to lateral index finger
– d. deep palmar arterial arch - formed by Radial artery (mainly). + deep branch of the ulnar a.
- three palmar metacarpal arteries - between metacarpals - join common palmar digitals

• three palmar metacarpal arteries
• three perforating arteries to dorsal arch

• a. formed by dorsal carpal branch from radial and ulnar arteries, and terminal branches of the anterior and posterior interosseus arteries. It is also joined by the perorating arteries from deep palmar arch.
• b. Dorsal arch gives off three dorsal metacarpal arteries, each then splits into dorsal proper digital arteries
• c. Dorsalis pollicis and dorsalis indicis can be considered as direct branches from radial dorsal carpal artery
• d. dorsal proper digital artery - to the medial side of little finger, direct branch from the dorsal arch
(or branch from the dorsal carpal branch from ulnar artery).

• 1. ulnar nerve - superficial branch of the ulnar nerve - enters palm on ulnar side of center; divides:
- three palmar digital branches - to skin of little finger (both sides), medial side ring finger
• 2. ulnar nerve - deep branch - to muscles of fine movements of hand
- hypothenar muscles, interosseous, medial lumbricals, adductor pollicis

• Enters palm to radial side of center; divides to 3 common palmar digital branches:
– a. 1st common to abductor pollicis brevis, flexor pollicis brevis, opponens pollicis, and 1st lumbrical muscle
• then it divides: - 3 proper palmar digital nerve - to skin, both sides of thumb; & lateral side of index
– b. 2nd common - to 2nd lumbrical muscle
• divides - to 2 proper palmar digital nerve - to skin of medial index, lateral middle finger
– c. 3rd common palmar digital branch divides to 2 proper palmar digital nerve. - to skin on medial middle, lateral ring finger

• all sensory innervation in hand (dorsal & lateral skin & fascia)

• Thenar / short thumb muscles

• ORIGIN
Flexor retinaculum, tubercle of trapezium bone, and tubercle of scaphoid bone
• INSERTION
Base of proximal phalanx of thumb, radial side, and extensor expansion
• ACTION
Abducts the carpometacarpal and metacarpophalangeal joints of the thumb in a vertical direction perpendicular to the place of the palm. By virtue of its attachment into the dorsal extensor expansion, extends the interphalangeal joint of the thumb. Assists in opposition, and may assist in flexion and medial rotation of the metacarpophalangeal joint.
• NERVE median nerve - C6, C7, C8, T1

FLEXOR POLLICIS BREVIS
• ORIGIN
– Superficial head: flexor retinaculum and trapezium bone
– Deep head: trapezoid and capitate bones
• INSERTION
Base of proximal phalanx of thumb, radial side, and extensor expansion
• ACTION
Flexes the metacarpophalangeal and carpometacarpal joints of the thumb, and assists in opposition of the thumb toward the little finger. By virtue of its attachment into the dorsal extensor expansion, may extend the interphalangeal joint
• NERVE
– superficial head: median nerve.
C6, C7, C8,
T1
– deep head: C8, T1

OPPONEN POLLICIS
• ORIGIN
Flexor retinaculum and tubercle of trapezium bone
• INSERTION
Entire length of first metacarpal bone, radial side
• ACTION
Opposes (i.e., flexes and abducts with slight medial rotation) the carpometacarpal joint of the thumb, placing the thumb in a position so that, by flexion of the metacarpophalangeal joint, it can oppose the fingers. For true opposition of the thumb and little finger, the pads of these digits come in contact. Bringing the tips of these digits together can be donw without opponens action
• NERVE median nerve - C6, C7, C8, T1

ADDUCTOR POLLICIS
• ORIGIN
– oblique head: capitate bone, and bases of second and third metacarpal bones
– transverse head: palmar surface of third metacarpal bone
• INSERTION
Transverse head into ulnar side of base of proximal phalanx of thumb, and oblique head into extensor expansion
• ACTION
Adducts the carpometacarpal joint, and adducts and assists in flexion of the metacarpophalangeal joint, so that the thumb moves toward the plane of the palm. Aids in opposition of the thumb toward the little finger.
By virtue of the attachment of the obilique fibers into the extensor expansion, may assist in extending the interphalangeal joint.
• NERVE ulnar never C8, T1

• Hypothenar / short muscles of little finger

ABDUCTOR DIGITI MINIMI
• ORIGIN
Tendon of flexor carpi ulnaris and pisiform bone
• INSERTION
By two slips: one into base of proximal phalanx of little finger, ulnar side; the second, into the ulnar border of the extensor expansion
• ACTION
Abducts, assists in opposition, and may assist in flexion of the metacarpophalangeal joint of the little finger; by virtue of insertion into the extensor expansion, may assist in extension of interphalangeal joints
• NERVE ulnar nerve - C(7), C8, T1

• ORIGIN hook of hamate bone, and flexor retinaculum
• INSERTION base of proximal phalanx of little finger, ulnar side
• ACTION
Flexes the metacarpophalangeal joint of the little finger and assists in opposition of the little finger toward the thumb
• NERVE ulnar never, C(7), C8, T1

• ORIGIN hook of hamate bone, and flexor retinaculum
• INSERTION entire length of fifth metacarpal, ulnar side
• ACTION opposes (i.e., flexes with slight rotation) the carpometacarpal joint of the little finger, lifting the ulnar border of the hand into a position so that the metacarpophalangeal flexors can oppose the little finger to the thumb.
Helps to cup the palm of the hand
• NERVE ulnar nerve - C(7), C8, T1

• Short Hand muscles

LUMBRICALS
• ORIGIN
– #1 and #2: radial surface of flexor profundus tendons of index and middle fingers, respectively.
– #3: adjacent sides of tendon of flexor digitorum profundus tendons of middle and ring fingers
– #4: adjacent sides of tendon of flexor digitorum profundus of ring and little fingers
• INSERTION
Into the radial border of the extensor expansion on the dorsum of the respective digits

• ACTION
Extend the interphalangeal joints and simutaneously flex the metacarpophalangeal joints of the second through fifth digits. The lumbricales also extend the interphalangeal joints when the metacarpophalangeal joints are extended. As the fingers are extended at all joints, the flexor digitorum profundus tendons offer a form of passive resistance to this movement. Since the lumbricales are attached to the flexor profundus tendons, they can diminish this resistive tension by contracting and pulling these tendons distally, and this release of tension decreases the contractile force needed by the muscles that extend the finger joints.
• NERVE
I, II: median nerve, C(6), 7, C8, T1 III, IV: ulnar nerve – C(7), C8, T1

• ORIGIN
– First, lateral head: Proximal one half of ulnar border of first metacarpal bone
– First, medial head: radial border of second metacarpal bone
– second, third, and fourth: adjacent sides of metacarpal bones in each interspace
• INSERTION into extensor expansions and to base of proximal phalanges as follows:
– First: radial side of index finger, chiefly to base of proxiaml phalanx
– Second: radial side of middle finger
– Third: ulnar side of middle finger, chiefly into extensor expansion
– Fourth: ulnar side of ring finger
• ACTION
Abducts the index, middle, and ring fingers from the axial line through the third digit. Assists in flexion of metacarpophalangeal joints and extension of interphalangeal joints of the same fingers. The first assists in addition of the thumb
• NERVE ulnar nerve C8, T1

• ORIGIN
– First: base of first metacarpal bone, ulnar side
– Second: length of second metacarpal bone, ulnar side
– Third: length of fourth metacarpal bone, radial side
– Fourth: length of fifth metacarpal bone, radial side
• INSERTION
Chiefly, into the extensor expansion of the respective digit, with possible attachement to base of proximal phalanx as follows
– First: ulnar side of thumb
– Second: ulnar side of index finger
– Third: radial side of ring finger
– Fourth: radial side of little finger
• ACTION
Adduction of thumb, index , ring, and little finger toward the axial line through the third digit. Assist in flexion of metacarpophalangeal joints, and extension of interphalangeal joints of the three fingers
• NERVE ulnar nerev C8, T1