Week 3 - Anatomy of the hand Flashcards
Which bones are involved in radiocarpal joint?
Distal surface of radius with scaphoid + lunate
Lunate only has partial contact when in neutral position
What is involved in the Ulnocarpal joint?
The WFC disc of the ulna comes into contact with the lunate and the triquetral
Which joints of the wrist have independent movement?
CM-1 - the joint of the thumb
Where is the radial flexor muscle of the forearm attached?
Base of metacarpal 2
Where are the two radial extensors of the forearm attached?
M2 and M3
Where are the ulnar muscles of the forearm attached?
M5
Why is the radiocarpal joint an independent joint of the other wrist joints?
It has a distinct capsule, separate from the others
Describe the two collateral ligaments of the wrist
Radial CL - radial styloid to scaphoid
Ulnar CL - ulnar styloid to triquetral
What are the two main ligaments between carpal bones you NEED to know?
Pisohamate
Pisometacarpal (pisiform to 5th metacarpal)
How are carpal ligaments named?
Dorsal or palmar, then by the bones they connect
What can flexors on the lateral side of the wrist do?
Abduct and flex, as they’re not attached absolutely centre
What can extensors on the lateral side of the wrist do?
Abduct and extend, as they’re not attached absolutely centre
What can the flexors and extensors of the medial side of the wrist do?
Adduct
What movement would you see if the lateral flexor and extensor contracted at the same time?
Abduction
Extension and flexion would cancel each other out
What is circumduction and why is it possible in the wrist?
The wrist is an ellipsoid type of synovial joint.
Circumduction is a circular movement, possible because of the shape of the joint
Performed in sequential movements
What is abduction limited by?
The radial styloid - it’s more distal
What limits adduction?
The radial collateral ligament
At which joint is abduction and adduction largely at?
The radiocarpal joint
What are the four landmarks of the carpal bones?
The hooks of the hamate and pisiform
The tubercles on the scaphoid and trapezium (like a ridge)
Where are the heads of the metacarpals?
The distal ends, while the proximal ends are the bases
What type of joints are the metacarpophalangeal joints?
Condyloid joints
Describe the movements around the MCP joints
Extension/flexion
Abduction/adduction
Rotation - rotation is not active, there are no rotator muscles
Where is the axis of movement of the hand?
A line down the third metacarpal
Which muscles perform movements at the metacarpals?
Interossei and lumbricals
What is the single, specific nerve for the interossei and lumbrical muscles?
The ulnar nerve
Which are the deeper muscles of the hand?
Interossei
How would an interossei tendon be attached to abduct a finger?
To the lateral side of the metacarpal
Is the abductor of the little finger interosseous?
No - there is no neighbouring metacarpal for attachment
Describe the dorsal interosseous muscles: What are their attachments? Where are they found? What do they do?
Each is attached to two neighbouring metacarpals. This makes them double headed and feather-like in appearance –> bi-pennate muscles
These are found in a relatively posterior plane
They abduct the index finger, the middle finger and the ring finger
How are there four interossei muscles but only three of the phalanges are abducted by them?
There are two attached to the middle finger - one on either side
What do the palmar interossei muscles do? How many are there?
These are the ADDUCTORS of the ring finger, index finger and the little finger
Does the thumb have any interossei muscles?
No - has it’s own adductors and abductors
Where does the FCR attach?
M2
Where does the FCU attach?
M5, via the pisiform bone
What is the flexor retinaculum? What is its purpose?
FR is a thick fibrous band, connected to the scaphoid and trapezium ridges, and the pisiform and hamate hooks
It keeps all of the wrist tendons in place, some of which merge with the band
Describe the adductor of the thumb
Two parts:
One runs transversely from the third metacarpal, the other runs obliquely from the retinaculum
Covers the lateral interosseous muscles of the second and third metacarpals
Where does the flexor digitorum profundus attach at the wrist/hand?
The distal phalanges–> covers all of the joints
Where does the flexor pollicis longus attach?
The distal phalanx of the thumb
Describe the lumbricals
These are long slender muscles, which arise from the lateral side of the flexor digitorum profundus tendons and insert onto the base of the four phalanges
Describe the orientation of the flexor digitorum superficialis to the flexor digitorum profundus
FDP is deep to the FDS
Describe how the FDS and FDP move around the phalanges
The FDS tendon is split into two parts right before the PIP, through which the FDP moves through to the distal phalanx
The FDS attaches to the middle phalannx
Which muscle/s act on the distal phalanges?
Flexor digitorum profundus
What makes up the carpal tunnel?
Carpal bones and the retinaculum
Which tendons pass through the carpal tunnel?
All LONG tendons, except flexor carpi ulnaris
–> nine tendons and the median nerve
Where does FCR pass through the wrist?
Though a separate compartment adjacent to the carpal tunnel
More accurate to say it passes in the flexor retinaculum
Describe tendon sheaths
Synovial sheaths of tendons that are double-layered tubular synovial sacs
One side is in contact with the tendon, outer layer contacts the surrounding tissues
Where is the common synovial sheath?
Extends beyond the flexor retinaculum, over the FDS tendons. Is continuous with the sheath of the little finger only
Does the synovial sheath of the thumb continue past the FR?
Yes
Describe the synovial sheaths in the phalanges
Index, ring and middle finger have sheaths that are discontinuous with the tendon sheaths in the FR
Where are strong fibrous sheaths over tendons in the hand, and why do we have them?
They are over the phalanges synovial sheaths, discontinuous over the IP joints.
Present because experience friction in the hand
What is the thenar eminence?
A group of three muscles at the base of the thumb - a short abductor, a short flexor and an opponens - moves metacarpal in apposition
What is the hypothenar eminence?
A group of three muscles at the base of the little finger - a short abductor, a short flexor and an opponens - moves metacarpal in apposition
What are the intrinsic muscles of the hand?
A OF A OF A
The thenar and hypothenar groups:
Abductor pollicis brevis
Opponens pollicis
Flexor pollicis brevis
(THENAR - 3)
Adductor pollicis
Opponens digiti minimi
Flexor digiti minimi brevis
Abductor digiti minimi
(HYPOTHENAR - 3)
Which nerve supplies the thenar muscles?
The median nerve
Which nerve supplies the hypothenar muscles?
Ulnar nerve
What is the palmar aponeurosis? What does it do?
The PA is the palmar fascia and bridges the gap between the thenar and hypothenar muscles of the palm
What structures are at the dorsal region of the phalanges?
Only long tendons, no muscles
Where would you find an extensor expansion?
On the extensor side of the phalanges, spanning proximal and middle phalanges
What is the purpose of extensor expansions?
These triangular fibrous sheets come from the tendons of the interossei and lumbrical muscles, forming a hood over the distal phalanx.
They are able to flex the PIP and extend the DIP
How do extensor expansions help with fine movements?
They coordinate and balance actions of the long muscles
How does the median nerve get into the hand?
Through the carpal tunnel
Which muscles does the median nerve innervate?
The thenar muscles and the lumbricals
Which muscles does the ulnar nerve innervate in the hand?
Hypothenar muscles and the cutaneous areas
A deep branch also goes to all of the other muscles
