Sievert: Forearm and Posterior Hand Flashcards
What are the three joints of the fingers?
MP: metacarpo-phalangeal between metacarpals and proximal phalanx
PIP: proximal interphalangeal between between proximal and middle phalanx
DIP: distal interphalangeal between middle and distal phalanx
Are there muscles associated with the posterior hand?
No muscles, just tendons of muscles of the forearm that are crossing the wrist.
How many phalanges are associated with each finger? How many are associated with each thumb?
3 for each finger: distal, middle, and proximal
2 for each thumb: distal and proximal
How many metacarpals are associated with each hand?
5
This is an apparatus that runs across the phalanges, giving off a central band and two lateral bands that come together and attach to the distal phalanx
extensor hood
When you pull on the extensor hood, what happens to tension in the central and lateral bands? What happens when you attach an extensor tendon to the hood?
When you pull on the hood, you cause increased tension in both of these bands. Attaching an extensor tendon to the hood causes extension at the PIP and DIP joints.
On which side of the extensor hood is the extensor tendon attached?
dorsal side
What do extensor tendons do?
Cause extension of all of the joints
The MP, PIP, and DIP joints can be acted on individually in the anterior hand digits. However, what happens to these joints when the extensor digitorum contracts?
Because of the arrangement of the extensor hood, all of these joints are extended at the same time in any single digit when the extensor digitorum contracts
The long extensor tendon gives off a central band. Where does this go? It also gives off a lateral band. Where does this go?
central band goes to the base of the middle phalanx; lateral band to distal phalanx
What do the lumbricals and interossei do?
extend interphalangeal joints
flex metacarpophalangeal joints
What does the flexor digitorum profundus do?
flexes the distal interphalangeal joint (DIP)
What does the flexor digitorum superficialis do?
flexes the PIP
Can you make a tight fist without the extendor tendons at the wrist?
No
T/F: Tendons passing through the compartments must be protected from wear by a synovial tendon sheath.
True
In the anterior and posterior forearm, when long muscles and their tendons cross into the wrist into the base of the metacarpals, what must they pass under?
the retinaculum
What is the purpose of the retinaculum?
It is a dense CT sheath that holds the tendons in place. It keeps the tendons nice and tight and prevents bow-stringing.
There is a retinaculum on the posterior side called the (blank) retinaculum, which corresponds to the (blank) retinaculum on the anterior side.
extensor; flexor
What allows tendons to slide smoothly beneath the retinaculum without causing damage to the tendons?
tubes filled with synovial fluid
Not a part of any muscle, it is a band around tendons that holds them in place. Its function is mostly to stabilize a tendon.
retinaculum
In which portion of the hand, dorsum or anterior side, are there more tendon sheaths? Can these sheaths become infected?
On the dorsum of the hand, tendon sheaths are more numerous. They can become infected.
Where do most posterior forearm muscles arise from?
from the common extensor tendon off of the lateral epicondyle or the supracondylar ridge of humerus
Which posterior forearm muscles DO NOT arise from the lateral epicondyle or supracondylar ridge?
3 thumb muscles (arise from radius, ulna, interosseus membrane)
extensor indices
supinator
All posterior forearm muscles are innervated by this nerve.
radial nerve (mostly deep branch)
How many muscles are there to the thumb? The fingers? The wrist? Muscles that don’t cross at the wrist?
THREE!
What does the snuffbox form between?
two extensor tendons: most posterior is the extensor pollicis longus, anterior: extensor pollicis brevis and abductor pollicis longus** most lateral (these two tendons run together)
What is it important to consider when thinking about the actions of the thumb?
The thumb is not in the same place as the fingers - it is 90 degrees from the plane of the fingers.
Describe abduction and adduction of the fingers. What is unique about the middle finger?
Abduction is moving away from the middle finger, while adduction is moving toward the middle finger. Middle finger can ONLY abduct in both directions.
In what plane do you flex and extend the fingers? On what axis is this motion occurring?
sagittal plane; transverse axis
On what plane do you flex and extend the thumb? On what axis is this motion occurring?
coronal plane; AP axis
What is adduction of the thumb? What’s abduction?
thumb moving close to the midline (palm); thumb moving away from midline
What’s extension of the thumb?
Hitchhiker thumb!
What are three posterior forearm thumb muscles, that do not arise from the lateral epicondyl and supracondylar ridge?
abductor pollicis longus
extensor pollicis brevis
extensor pollicis longus
Which muscle to the thumb is more toward the anterior surface and most lateral? This muscle goes to the base of the metacarpal and crosses 1 joint.
abductor pollicis longus
Which muscle to the thumb runs along the same line as the abductor pollicis longus, goes to the proximal phalanx, and crosses 2 joints?
extensor pollicis brevis