Hand Flashcards

1
Q

Median nerve

A
  • The median nerve contains anterior division fibers C6 - T1, and thereby innervates mostly flexors within the forearm and hand.
  • Innervates five muscles in the hand: the 3 muscles of the thenar eminence at the base of the thumb, and 2 lumbricals for the second and third digits. On the cutaneous side, the median nerve innervates the palmar surface of the lateral 3½ digits, as well as their nail beds.
  • Also innervates all muscles of the anterior forearm except one and a half (the flexor carpi ulnaris and the medial half of the flexor digitorum profundum).
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2
Q

Ulnar nerve

A
  • Ulnar nerve innervates all of the intrinsic hand muscles not innervated by the median nerve
    • Innervates the hypothenar eminence, and most intrinsic hand muscles (contains T1)
    • Just not the thenar eminence
  • (It also innervates the flexor carpi ulnaris and the medial half of the flexor digitorum profundus in the anterior forearm.)
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3
Q

What is the anastamosis of radial and ulnar arteries?

A
  • The radial artery and the ulnar artery anastomose in the hand, by forming two arches, the superficial palmar arch, and the deep palmar arch
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4
Q

thenar eminence

  • What does it allow us to do
  • Muscles?
  • Innervation?
A
  • Intrinisc, At base of thumb
  • The bigger of the two eminences
  • 3 muscles that give us the ability to oppose our thumb
    • OAF
      • Opponence muscle - opponens pollicis
        • ​Allows us to roll thumb
      • ABductor muscle - abductor pollicis brevis (move in sagittal plane)
      • Flexor muscle - flexor pollicis brevis
        • Allows us to sweep thumb across flexed digits
  • Innervated by recurrent branch of the median nerve
    • Very important, clinically significant
    • (whereas hypothenar innervated by ulnar nerve)
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5
Q

hypothenar eminence

  • Muscles?
  • Innervation?
A
  • At base of pinkie
  • The less important eminence
  • 3 muscles, OAF
    • Opponens digiti minimi
    • ABductor digiti minimi
    • Flexor digiti minimi
  • Innervated by ulnar nerve
    • ​(whereas thenar innervated by recurrent branch of median nerve)
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6
Q

palmar aponeurosis

  • Where is it?
  • Why do we have it?
  • What muscle sometimes inserts into it?
A
  • A broad aponeurois (connective tissue) which tightly attaches to the fascia under the skin
  • Protects all the important stuff in the palm (blood vessels, nerves)
  • The palmaris longus is a mysterious muscle that inserts into the palmar aponeurosis
    • absent in 15% of the population
  • Thenar eminence and hypothenar eminences are positioned on the sides of the palmar aponeurosis.
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7
Q

intrinsic hand muscles

A
  • “intrinsic” means they start and end in the hand
  • Protected by palmar aponeurosis
  • Thenar and hypothenar eminences (3 each, OAF - opponens, abductor, flexor)
    • The opponens pollicis and abductor pollicis brevis = innervated by the median nerve. The flexor pollicis brevis has two heads a superficial and a deep. The superficial is innervated by the median nerve and the deep is innervated by the ulnar nerve
  • 4 Lumbricals“wormlike”
    • Deep in palm of hand
    • Unusual in that don’t attach to bone - Attached to flexor digitorum profundus tendons
    • 1st and 2nd - innervated by median
    • 3rd and 4th - innervated by ulnar nerve
  • interosseous muscles“DAB”
    • Allows us to finger spread and bring together
    • 2 sets - 4 dorsal (2 on the middle finger)
      • not needed by thumb or pinkie
    • found between metacarpals
    • innervated by ulnar nerve
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8
Q

extrinsic hand muscles

A
  • “extrinsic” means they start in the forearm, and send tendons into hand
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9
Q

What’s the million dollar nerve?

A
  • Recurrent branch of the median nerve
  • Innervates the three thenar muscles
  • “Recurrent” because it bends back on itself
  • It’s prone to injury because it’s superficial
  • Without it, no power grip
  • Hand surgeons have to be careful when correcting carpal tunnel syndrome
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10
Q

Metacarpal Phalangeal (MP) joints

  • Muscle to abduct, adduct?
  • Muscle to extend, flex?
A
  • These are the knuckle joints (there are 4)
  • They are condyloid (biaxial) because allow movements in two planes
  • Abduction and adduction = intrinsic hand muscles
    • Abduction = spreading fingers
    • ADduction = making fingers come back together
    • Around midline in middle finger
  • Flexion and extension = forearm muscles
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11
Q

Proximal Interphalangeal (PIP) joint

  • What actions are possible?
A
  • There are two InterPhalangeal joints, this is the more proximal one
  • Pure hinge joints
    • Only permit flexion and extension
    • Like the elbow
      *
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12
Q

Distal Interphalangeal (DIP) joint

  • What actions are possible?
A
  • There are two InterPhalangeal joints, this is the more distal one
  • Pure hinge joints
    • Only permit flexion and extension (sagittal plane)
    • Like the elbow
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13
Q

Compare and contrast the actions of lumbricals and interosseous muscles, their innervation and joints where they act

A
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14
Q

How do we make a fist?

A
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15
Q

Most important digit of upper limb?

What’s special about it?

A
  • The thumb!
  • Has highly mobile metacarpal
    • carpometacarpal (CMC)
    • We can move the thumb in all the planes
  • Only has a single phalanx bone. So the thumb only has two phalanges, whereas each finger has three.
  • Moves differently, has its own planes
    • Flexion/extension occurs in coronal plane (whereas fingers in sagittal plane)
      • When flex thumb, sweeping it across the palm
    • Abduction/Adduction in sagittal plane
      • When abduct thumb, move it forward)
  • Thumb opposition involves abduction, flexion, medial rotation. Allows us to:
    • Touch pads of other digits
    • Makes a power grip - oppose thumb across flexed digits
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16
Q

metacarpal bones

A
  • 5 of them
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17
Q

number the digits in the hand

A
  • Thumb = #1, so it’s the first metacarpal
  • pinkie = #5
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18
Q

bones of the wrist

A
  • All 5 metacarpals articulate with distal row of carpal bones
  • There are two rows of carpal bones:
    • Trapezium, trapezoid, capitate (largest bones in the wrist), hamate
    • Scaphoid, lunate, triquetrum, pisiform
  • “Some Lovers Try Positions That They Can’t Handle”
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19
Q

What happens when thumb opposition is weak?

What isn’t working?

A
  • Then grip is weak
  • Opposition of the thumb involves abduction, flexion, and medial rotation of the thumb
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20
Q

pollicis

A
  • pollicis = thumb
  • 3 thenar muscles of thumb have pollicis in their name:
    • Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis
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21
Q

What’s the innervation of intrinsic hand muscles?

A
  • Ulnar nerve
    • C8, T1 fibers
    • T1 goes to hand
  • This is the default answer because of the proximal to distal gradient!
  • The only other possibility is the median nerve, it’s the only other one with T1 fibers
  • All interosseous muscles of the hand, with the exception of the first and second lumbricals (the most radial two are innervated by the median nerve), are innervated by the deep branch of the ulnar nerve
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22
Q

lumbricals

  • Numbering?
  • Where do they arise from?
  • What do they attach to?
  • Innervation?
  • Actions?
A
  • Arise from flexor tendons and attach to extensor tendons
    • Arise from Flexor digitorum profundus tendons
    • Pass anterior to joint, form “dorsal hoods” and attach to tendons of the Extensor Digitorum muscle
  • Innervation
    • ​Median nerve innervates the index and middle fingers (1st and 2nd)
    • Ulnar nerve innervates the ring and pinkie (3rd and 4th)

The only muscles that give ability to extend fingers!

  • Flex at MP joints
    • Pass anterior to the MP joints (anterior to knuckles at base of hand) –> flex there
    • (The extensor digitorum extends at MP)
  • Extend at PIP and DIP joints
    • It’s the lumbricals that extend all of the interphalangeal joints (proximal and distal), all 4 fingers. ​
23
Q

divisions of the hand

A
24
Q

action of lumbricals

A
  • Simultanesously flex at MP joints and extend at IP joints
  • Lumbrical action is to hold a pea, that is to flex the metacarpophalangeal joint and extend the interphalangeal joints. When look at hand in this position, can see this makes an “L” shape, since L is for Lumbrical.
25
Q

Why is the name “extensor digitorum” an overstatement?

What is its innervation?

A
  • The name overestimates its true power:
    • Extensor digitorum can only extend your fingers at the MP (knuckle) joints
  • When you extend your fingers, the extensor digitorum canNOT extend all 4 fingers at the interphalangeal joint. No farther than knuckles.
    • Lumbricals give ability to extend all the way. (2 by 2 innervation)
  • Innervated by radial nerve
26
Q

how do lumbricals and extensor digitorum tendon work together?

A
  • Extensor digitorum tendon extends the fingers at the MP (knuckle) joints
  • Lumbricals insert into extensor digitorum tendon and extend the fingers at the IP joints
27
Q

anatomic snuff box

A
  • The tendons of the extensor pollicis longus and extensor pollicis brevis form what is known as the anatomical snuff box - an indentation on the lateral aspect of the thumb at its base
  • If localised pain is reported in the anatomical snuffbox, a fracture of the scaphoid is the most likely cause –> risk of avascular necrosis and arthritis
28
Q

describe the 5 movements of thumb

A
29
Q

what are the nerves responsible for thumb movements:

  • Abduction
  • Adduction
  • Extension
  • Flexion
  • Opposition
A
  • Abduction - median nerve
  • Adduction - ulnar nerve
  • Extension - radial nerve
  • Flexion - median nerve
  • Opposition - median nerve
  • The thenar muscles = opponens pollicis, abductor pollicis brevis, flexor pollicis brevis, and adductor pollicis muscles. All are innervated by the median nerve, except for the adductor pollicis and deep head of the flexor pollicis brevis, which are innervated by the ulnar nerve
30
Q

flex thumb using what nerves?

A
  • median nerve, innervates flexor pollicus longus tendon
31
Q

Which 3 nerves control finger extension?

What kinds of fibers?

A
  • Median and ulnar nerves
    • Anterior division fibers
    • (so these 2 are a special exception)
  • Radial nerve
  • Pollicus longus tendon extends the thumb
    • Median nerve
  • Lumbricals extend the IP joints of all fingers (and flex MP joints)
    • Median nerve innervates the index and middle fingers (1st and 2nd)
    • Ulnar nerve innervates the ring and pinkie (3rd and 4th)
  • Extensor digitorum extends fingers at MP (knuckle joint)
    • Radial nerve (this make sense bc radial nerve innervates extensors everywhere for posterior upper limb)
32
Q

extend thumb

A
  • Thumb is extended by two muscles that are innervated by the radial nerve (good!)
    • Extensor Pollicis Brevis and Extensor Pollicis Longus
33
Q

interosseous muscles

what are they for?

Which digits don’t have them?

Innervation?

A
  • intrinsic to the hand, between metacarpals
  • dorsal interosseous muscles = DAB muscles - abduct, allow us to finger spread at the knuckle joints
    • On both sides of the middle finger, do both AB and ADduction of middle
    • Not needed by thumb or pinkie
      • Pinkie has its personal ABductor digitiminimi in the thenar eminence
      • Thumb has its personal ABductor in the thenar eminence (abductor pollicis brevis)
  • 2 sets - 4 dorsal (2 on the middle finger)
  • Innervation = ulnar nerve
34
Q

which nerve gives ability to finger spread?

A
  • ulnar nerve
  • the ulnar nerve is the default innervator of intrinsic hand muscles
    • innervates all interosseous muscles, both palmar and dorsal
    • also innervates the adductor pollicis, for the thumb
35
Q

adduct fingers

  • Muscles?
  • Innervation
A
  • 3 palmar interosseous muscles“PAD muscles”
    • for index, ring, and little fingers
    • Don’t need for middle finger, because dorsal interosseous muscles that attach to middle finger do both
    • Don’t need for thumb, because it has its own personal ADuctor, the aductor pollicis deep in palm of hand
  • ADduct, so fingers touch each other again
  • All interosseous muscles (both palmar and dorsal) are innervated by deep branch of ulnar nerve
36
Q

What gives us the exclusive power to flex our distal phalanx at each of the four fingers?

A
  • tendons of the flexor digitorum profundus muscle
    • arises in the flexor forearm
    • also helps with flexing at other joints, but its major action is at last joint, the distal phalanx
  • Innervated by median nerve
37
Q

default nerve for flexor foream muscles?

A
  • median nerve and its branches
38
Q

default nerve for innervation of flexor ARM muscles?

A
  • musculocutaneous
    • The musculocutaneous nerve innervates the muscles in the anterior compartment of the arm – the biceps brachii, brachialis and coracobrachialis. These muscles flex the upper arm at the shoulder and the elbow. In addition, the biceps brachii also performs supination of the forearm.
39
Q

default nerve for intrinsic hand muscles

A
  • ulnar nerve
    • All interosseous muscles of the hand, with the exception of the first and second lumbricals (the most radial two are innervated by the median nerve), are innervated by the deep branch of the ulnar nerve.
    • anterior division fibers
40
Q

innervation of flexor digitorum profundus

and lumbricals?

A
  • flexor digitorum profundus innervation matches the innervation of the lumbricals:
    • those that go to index and middle finger are innervated by median nerve
      • ​Median nerve innervates 1st and 2nd
    • those going to ring and pinkie are innervated by ulnar nerve
      • Ulnar nerve innervates 3rd and 4th
41
Q

flexor digitorum superficialis -

what’s significant about it?

A
  • innervated by median nerve, which runs deep to it
  • gives exclusive ability to flex middle phalanges at PIP
    • since most distal joint is most important place where muscle acts
  • Innervated by median nerve
    • (default answer for flexor forearm)
  • in the intermediate layer of flexor muscles in anterior forearm
42
Q

wrist flexors and extensors

A
  • 2 flexor carpi muscles:
    • flexor carpi radialis, flexor carpi ulnaris
      • Flexor carpi radialis innervated by median nerve
      • Flexor carpi ulnaris innervated by ulnar nerve
  • 3 extensor carpi muscles: wrist extensors
    • All innervated by radial nerve
    • (extensor carpi ulnaris, extensor carpi radialis longus/brevis)
43
Q

where is the major action of:

the flexor digitorum profundus?

flexor digitorum superficialis?

lumbricals?

interosseous muscles

A
  • Flexor digitorum profundus - DIP
  • Flexor digitorum superficialis - PIP
  • Lumbricals - IPS (and also MP)
    • The major muscles that extend all four fingers at both the interphalangeal joints
    • share their innervation between median and ulnar nerve
  • Extensor digitorum - MP
    • Just the knuckles
  • Dorsal interosseous vs. palmar interosseous
    • Dorsal abduct “DAB” at MP joints
    • Palmar adduct “PAD” at MP joints
    • All innervated by branches of ulnar nerve
44
Q

blood supply to forearm and hand

A
  • have primary blood supply and back-up blood supply
  • Brachial artery splits into the ulnar artery and radial artery at the cubital fossa (anterior to the elbow)
    • They run close to their respective bones.
    • Radial artery supplies posterior forearm, ulnar supplies anterior.
  • Ulnar artery gives rise to superficial palmar arch –> palmar ulnar digital arteries –> supply medial and lateral sides of every thumb/finger
  • Radial artery –> deep palmar arch –> supplies thumb and lateral index finger
  • The two arches can anastamose with each other.
    • Readily available collateral blood supply
45
Q

what lies under the aponeurosis of the palm?

A
  • First thing you see under the palm’s aponeurosis is the superficial palmar arch, on the medial side of the palm
    • Comes from the ulnar artery
    • (Whereas the radial artery gives rise to deep palmar arch)
46
Q

dorsal interossei vs palmar interossei

  • where do they (both) act?
  • What’s the difference in their action
A
  • Dorsal abduct “DAB
  • Palmar adduct “PAD
  • All at MP joints
  • All innervated by branches of ulnar nerve
47
Q

Nerves that control thumb movements?

  • ABduction (2)
  • ADduction
  • Extension
  • Flexion
  • Opposition
A
  • 3 nerves control thumb:
    • Radial - ABduction, extension,
    • Median - ABduction, flexion, opposition
    • Ulnar - ADduction
  • Abduction: 2 muscles and 2 nerves
    • Abductor pollicis longus - radial nerve (in extensor compartment)
    • Abductor pollicis brevis - recurrent branch of median nerve (in thenar eminence)
    • So unusual for patient to totally lose ability to oppose thumb
  • Adduction:
    • Adductor pollicis - ulnar nerve (shares interosseus innervation)
  • Extension:
    • ​Extensor pollicis longus, brevis, extensor digitorum
    • posterior interosseus branch of radial nerve (controls extension of anything except fingers beyond MPs)
  • Flexion:
    • Flexor pollicis brevis
    • Flexor pollicis longus (one of the 9 tendons through the carpal tunnel) - anterior interosseus branch of median nerve
  • Opposition (for power grip)
    • muscles in thenar eminence innervated by recurrent branch of median nerve
    • ulnar nerve to a lesser extend (hypothenar eminence to pull pinkie over)
48
Q

what can’t the thumb do if…

  • Radial nerve is lesioned
  • Median nerve is lesioned
  • Ulnar nerve is lesioned
A
  • Radial - ABduction, extension,
  • Median - ABduction, flexion, opposition
  • Ulnar - ADduction
49
Q

what’s important at this point

A
  • Carpal-metacarpal joint
    • Formed by distal row of carpal bones, specifically the trapezium, and the first metacarpal - where most of thumb actions take place
50
Q
A
51
Q

name hand bones and joints

A
52
Q

which finger joints allow for more motion?

A
  • The interphalangeal joints are relatively restricted in action; they are simple hinge joints that permit only flexion and extension.
  • The metacarpophalangeal joints also permit flexion and extension, as well as abduction (finger spreading) and adduction
53
Q

nerves and muscles involved for flexion and extension of fingers:

Digits 2 + 3:

  • MCP joint:
  • PIP joint:
  • DIP joint:

Digits 4 + 5:

  • MCP joint:
  • PIP joint:
  • DIP joint:
A

Digits 2 + 3:

  • MCP joint: flexion by lumbricals (median nerve), extension by extensor digitorum (radial)
  • PIP joint: flexion by flexor digitorum superficialis (median nerve), extension by lumbricals (median nerve)
  • DIP joint: flexion by flexor digitorum profundus (median nerve), extension by lumbricals (median nerve)

Digits 4 + 5:

  • MCP joint: flexion by lumbricals (ulnar nerve), extension by extensor digitorum (radial)
  • PIP joint: flexion by flexor digitorum superficialis (median nerve), extension by lumbricals (ulnar nerve)
  • DIP joint: flexion by flexor digitorum profundus (ulnar nerve), extension by lumbricals (ulnar nerve)
54
Q

List all joints where a muscle or muscles innervated by the radial nerve act as extensors.

A

A,B,E,H,I

Muscles which produce MCP joint extension, all innervated by PIN branch of radial nerve:

  • Thumb: Extensor Pollicis Brevis and Extensor Pollicis Longus (PIN)
  • Index: Extensor Indicis (PIN)
  • Index, middle, ring and pinkie: Extensor Digitorum (PIN)
  • Pinkie: Extensor Digiti Minimi (PIN)