Hand Flashcards
Median nerve
- 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).
Ulnar nerve
- 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.)
What is the anastamosis of radial and ulnar arteries?
- The radial artery and the ulnar artery anastomose in the hand, by forming two arches, the superficial palmar arch, and the deep palmar arch
thenar eminence
- What does it allow us to do
- Muscles?
- Innervation?
- 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
-
Opponence muscle - opponens pollicis
- “OAF”
- Innervated by recurrent branch of the median nerve
- Very important, clinically significant
- (whereas hypothenar innervated by ulnar nerve)
hypothenar eminence
- Muscles?
- Innervation?
- 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)
palmar aponeurosis
- Where is it?
- Why do we have it?
- What muscle sometimes inserts into it?
- 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.
intrinsic hand muscles
- “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
extrinsic hand muscles
- “extrinsic” means they start in the forearm, and send tendons into hand
What’s the million dollar nerve?
- 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
Metacarpal Phalangeal (MP) joints
- Muscle to abduct, adduct?
- Muscle to extend, flex?
- 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
Proximal Interphalangeal (PIP) joint
- What actions are possible?
- 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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Distal Interphalangeal (DIP) joint
- What actions are possible?
- There are two InterPhalangeal joints, this is the more distal one
-
Pure hinge joints
- Only permit flexion and extension (sagittal plane)
- Like the elbow
Compare and contrast the actions of lumbricals and interosseous muscles, their innervation and joints where they act
How do we make a fist?
Most important digit of upper limb?
What’s special about it?
- 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)
-
Flexion/extension occurs in coronal plane (whereas fingers in sagittal plane)
- Thumb opposition involves abduction, flexion, medial rotation. Allows us to:
- Touch pads of other digits
- Makes a power grip - oppose thumb across flexed digits
metacarpal bones
- 5 of them
number the digits in the hand
- Thumb = #1, so it’s the first metacarpal
- pinkie = #5
bones of the wrist
- 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”
What happens when thumb opposition is weak?
What isn’t working?
- Then grip is weak
- Opposition of the thumb involves abduction, flexion, and medial rotation of the thumb
pollicis
- pollicis = thumb
- 3 thenar muscles of thumb have pollicis in their name:
- Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis
What’s the innervation of intrinsic hand muscles?
-
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