The Hand Flashcards
What structures contribute to hand function?
Forearm muscles, long tendons, and the lumbricals.
What are the three groups of small muscles in the hand?
Thenar, hypothenar eminences, and intrinsic palm muscles.
How is finger abduction defined?
Movement away from the middle finger.
How is finger adduction defined?
Movement towards the middle finger.
What movement is achieved through combined muscle action in the thumb?
Opposition.
Where do the lumbrical muscles originate and insert?
From radial sides of FDP tendons and insert into the extensor apparatus.
Which nerve innervates the lateral 2 lumbricals?
Median nerve.
Which nerve innervates the medial 2 lumbricals?
Ulnar nerve.
What are the functions of the lumbricals?
Flexion at MCP joints and extension at IP joints.
What are the muscles of the thenar eminence?
Opponens pollicis, abductor pollicis brevis, flexor pollicis brevis.
What nerve innervates the thenar muscles?
Median nerve.
What is the function of adductor pollicis and its innervation?
Adduction of the thumb; innervated by the ulnar nerve.
What are the functions of the interosseous muscles?
Abduction (dorsal interossei), adduction (palmar interossei), flex MCP joints, extend IP joints.
Which arteries supply the hand?
Radial and ulnar arteries.
What do the radial and ulnar arteries form in the hand?
Superficial and deep palmar arches.
What is the function of the superficial palmar arch?
Gives rise to digital branches to the fingers.
Where is the deep palmar arch located?
Deeper than the superficial arch, contributing to deep hand structures.
How many digital nerves supply each digit?
Four digital nerves per digit.
What should be considered in a ring block of a digit?
All four digital nerves must be anesthetized.
What typically accompanies digital arteries?
Digital nerves.
What can a laceration of a digital artery also damage?
The accompanying digital nerve.
Which muscles of the hand does the median nerve supply?
Thenar muscles and lateral 2 lumbricals.
What kind of loss occurs with median nerve damage?
Motor loss (especially opposition and abduction of thumb) and sensory loss on lateral palm and digits.
What is the main motor supply of the ulnar nerve in the hand?
Most small hand muscles, including interossei and medial 2 lumbricals.
What type of motor loss occurs with ulnar nerve injury?
Loss of adduction and fine motor control.
What does the radial nerve control in the hand?
Wrist and finger extension (weak if injured), no motor to intrinsic hand muscles.
Which area does the radial nerve supply sensory innervation to?
Dorsal thumb, index, middle fingers (not tips), part of hand.
What is the result of radial nerve damage at the wrist?
Weak wrist extension (wrist drop).
What fingers are innervated by the ulnar nerve?
The little finger and half of the ring finger.
How many bones are there in the hand and wrist combined?
27 bones.
Name the 3 groups of hand bones.
Carpal bones (8), metacarpals (5), phalanges (14).
How many phalanges does the thumb have?
Two (proximal and distal).
Which carpal bone is most commonly fractured?
Scaphoid.
Which carpal bone is prone to dislocation?
Lunate.
Which carpal bone has a hook that can be damaged?
Hamate.
What forms the anterior wall of the carpal tunnel?
Flexor retinaculum.
What forms the roof and sides of the carpal tunnel?
The arch of the carpal bones.
What tendon inserts into the base of the distal phalanx?
Flexor digitorum profundus (FDP).
What is the function of the lumbricals?
Flexion of MCP joints, extension of IP joints, fine control (e.g., writing).
: How many lumbricals are there, and where do they originate?
4, originating from the radial sides of FDP tendons.
Which nerves supply the lumbricals?
Radial 2 by median nerve, ulnar 2 by ulnar nerve.
What muscles make up the thenar eminence?
Opponens pollicis, abductor pollicis brevis, flexor pollicis brevis.
What nerve supplies most thenar muscles?
Median nerve.
What is the innervation of adductor pollicis?
Ulnar nerve.
What muscles make up the hypothenar eminence?
Abductor digiti minimi, flexor digiti minimi, opponens digiti minimi.
How many palmar interossei are there, and what is their function?
3; they adduct the digits (PAD).
How many dorsal interossei are there, and what is their function?
4; they abduct the digits (DAB).
What nerve innervates all interosseous muscles?
Ulnar nerve.
What complex action is enabled by the small muscles of the hand?
Opposition, fine motor skills (e.g., piano playing).
What causes the “hand of benediction”?
Median nerve injury – seen when attempting to make a fist.
What causes the “ulnar claw”?
Ulnar nerve injury – results in permanent flexion of 4th and 5th digits.
What is the ulnar paradox?
The more proximal the ulnar injury, the less severe the claw (closer to the paw, worse the claw).
What is wrist drop a sign of?
Radial nerve injury – weak wrist and finger extension.
What two arteries form the arterial supply of the hand?
Ulnar and radial arteries.
What arches are formed by these arteries?
Superficial and deep palmar arches.
What do digital arteries branch from?
Common palmar digital arteries → proper digital arteries.
How many digital nerves supply each finger?
Four per digit.
