Hand Muscles
Summary
TLDRThis tutorial delves into the intrinsic muscles of the hand, focusing on the thenar, hypothenar, lumbrical, and interosseous muscles. It explains their actions, innervation by the median and ulnar nerves, and the unique function of the lumbricals in flexing the metacarpophalangeal joints and extending the interphalangeal joints. The video script also covers the anatomy and function of the adductor pollicis and the interosseous muscles, highlighting their role in thumb movement and finger abduction/adduction, respectively.
Takeaways
- π€ The intrinsic hand muscles originate and insert in the hand, providing dexterity but less power compared to extrinsic muscles.
- π The thenar muscles act on the thumb, including the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis, and are innervated by the recurrent branch of the median nerve.
- π€ The hypothenar muscles act on the pinky finger, with actions of abduction, flexion, and opposition, and are innervated by the ulnar nerve after it traverses Guyon's canal.
- π€ The lumbrical muscles arise from the flexor digitorum profundus tendons and have a unique action of flexing the metacarpophalangeal (MCP) joint while extending the interphalangeal (IP) joints.
- π The median nerve provides innervation to the first two lumbrical muscles for the index and middle finger, while the ulnar nerve innervates the third and fourth lumbricals for the ring and pinky fingers.
- π€ The adductor pollicis has a transverse and an oblique head, both originating from the third metacarpal and carpal bones, and is responsible for thumb adduction.
- π The interosseous muscles, with a dorsal and palmar set, are involved in the abduction and adduction of the fingers, respectively, and are innervated by the ulnar nerve.
- π The acronym 'PAD' stands for palmar interossei muscles that adduct the digits, while 'DAB' stands for dorsal interossei muscles that abduct the metacarpophalangeal joints.
- π€οΈ The median nerve courses through the carpal tunnel and sends branches to the thenar muscles and the first two lumbricals, while the ulnar nerve traverses Guyon's canal to innervate the hypothenar muscles and the third and fourth lumbricals.
- π The knowledge of the actions and innervation of these hand muscles is crucial for understanding conditions like claw hand and for medical board preparation.
Q & A
What are the intrinsic hand muscles?
-The intrinsic hand muscles are muscles that originate and insert in the hand. They are responsible for fine motor movements and dexterity, unlike the extrinsic muscles which provide power but less dexterity.
What are the three main muscles that act on the thumb?
-The three main muscles that act on the thumb are the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. These muscles are responsible for thumb abduction, flexion, and opposition, respectively.
Which nerve provides motor innervation to the thenar muscles?
-The median nerve provides motor innervation to the thenar muscles. It sends a branch called the recurrent branch of the median nerve after traversing the carpal tunnel.
What is the role of the hypothenar muscles in hand function?
-The hypothenar muscles act on the pinky finger. They include the abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi, and are responsible for abduction, flexion, and opposition of the pinky finger.
How does the median nerve innervate the hypothenar muscles?
-The median nerve innervates the hypothenar muscles after traversing the carpal tunnel and sending a branch called the recurrent branch of the median nerve.
What are the lumbar muscles and what is their function?
-The lumbar muscles are four in number and arise from the flexor digitorum profundus tendons. They help in flexing the metacarpophalangeal (MCP) joints and extending the interphalangeal (IP) joints, contributing to fine hand movements.
Which nerve innervates the lumbar muscles?
-The median nerve innervates the first two lumbar muscles (for the index and middle fingers), while the ulnar nerve innervates the third and fourth lumbar muscles (for the ring and pinky fingers).
What is the function of the adductor pollicis muscle?
-The adductor pollicis muscle, which has a transverse head and an oblique head, is responsible for adducting the thumb towards the palm.
What are the interosseous muscles and how do they affect finger movements?
-The interosseous muscles are two sets: the dorsal and palmar interosseous muscles. The dorsal interosseous muscles abduct the fingers away from the midline, while the palmar interosseous muscles adduct the fingers towards the midline.
Which nerve innervates the interosseous muscles?
-The interosseous muscles are innervated by the ulnar nerve, which also provides innervation to the hypothenar muscles.
What is the significance of the extensor expansion hood in relation to the lumbar muscles?
-The extensor expansion hood is significant because the pull of the lumbar muscles on this hood helps in flexing the MCP joints and extending the IP joints, contributing to the unique action of the lumbar muscles.
Outlines
π€ Intrinsic Hand Muscles and Their Functions
This paragraph delves into the anatomy and function of the intrinsic hand muscles, focusing on the thenar, hypothenar, lumbrical, and interosseous muscles. The thenar muscles, which include the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis, are responsible for thumb movements such as abduction, flexion, and opposition, crucial for dexterity in tasks like buttoning a collar or shaking hands. These muscles are innervated by the recurrent branch of the median nerve after it traverses the carpal tunnel. The hypothenar muscles, which act on the pinky finger, include the abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi, and are also innervated by the ulnar nerve after passing through Guyon's canal. The paragraph emphasizes the importance of these muscles for fine motor skills and their representation in the somatotopic map of the precentral gyrus.
π€ Lumbrical Muscles and Their Unique Actions
The second paragraph discusses the unique action of the lumbrical muscles, which arise from the flexor digitorum profundus tendons and insert on the extensor expansion hood. These muscles have the distinct function of flexing the metacarpophalangeal (MCP) joints while simultaneously extending the interphalangeal (IP) joints. This dual action is facilitated by the lumbrical muscles' position relative to the MCP and IP joints. The median nerve, after sending a branch to the thenar muscles, innervates the first two lumbricals, while the ulnar nerve, after traversing Guyon's canal, innervates the remaining two lumbricals that act on the ring and pinky fingers. The paragraph also touches on the clinical relevance of understanding these muscle actions for diagnosing conditions like claw hand.
Mindmap
Keywords
π‘Intrinsic hand muscles
π‘Thenar muscles
π‘Hypothenar muscles
π‘Lumbrical muscles
π‘Gon's canal
π‘Median nerve
π‘Adductor pollicis
π‘Interosseous muscles
π‘Carpal tunnel
π‘Extensor expansion hood
Highlights
Introduction to intrinsic hand muscles, which originate and insert in the hand, providing dexterity.
Extrinsic hand muscles, like FDP, FDS, FPL, EDC, originate in the forearm and have long tendons in the hand, providing power.
Thear muscles act on the thumb, including abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis.
The median nerve innervates the thenar muscles through the recurrent branch after traversing the carpal tunnel.
Hypothenar muscles act on the pinky, including abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi.
The ulnar nerve provides innervation to the hypothenar muscles after traversing Guyon's canal.
Lumbrical muscles arise from the flexor digitorum profundus tendons and insert on the extensor expansion hood.
Lumbrical muscles uniquely flex the MCP joint and extend the IP joints, affecting hand movement.
The median nerve innervates the first two lumbrical muscles, affecting the index and middle finger.
The ulnar nerve innervates the third and fourth lumbrical muscles, affecting the ring and pinky fingers.
The adductor pollicis has a transverse head and an oblique head, both originating from the third metacarpal and carpal bones.
The adductor pollicis muscle contracts to perform thumb adduction.
The dorsal and palmar interossei muscles are responsible for abduction and adduction of the fingers.
The dorsal interossei muscles are involved in abduction at the metacarpophalangeal joints.
The palmar interossei muscles adduct the digits, pulling them towards the midline.
The interossei muscles are often referred to as 'PADs' (palmar adduct) and 'DABs' (dorsal abduct).
The ulnar nerve innervates the interossei muscles, affecting finger movement.
Transcripts
okay let's talk about the hand muscles
now in this uh tutorial we're going to
talk about the uh theer hypothenar
muscles and the adductor policis the
lumbal and the Neurosis muscles their
actions and their ination and we'll
throughout this we'll talk about gon's
Canal okay hand and the Hand muscles
I've called this called the intrinsic
hand muscles because these are muscles
that are originate and insert in the
hand there's a lot of tendons that go to
the hand like fdp fds FPL EDC but these
muscles originate in the forearm or even
in the arm in some cases and then their
long tendons go into the hand so they
have great power not a lot of dexterity
our intrinsic hand muscles the following
list don't have as much power in fact
they're fatigued easier but they have a
lot of dexterity which is also why if
you remember in the homunculus so much
time so much uh uh
somatotopic um space has been or uh
dedicated to hand muscles in the preor
pre Central gyrus all right let's start
with the thear muscles thear muscles are
muscles that act on the thumb and
there's three of them abductor Pocus
brevis flexor Pocus brevis and
opponent's Pocus and there they are for
the abbreviations
afo on the thumb muscles and whether you
can identify those three individual
muscles on a picture or Cav doesn't
matter to me the main thing is to
recognize the actions we have an
abductor of the thumb a flexer of the
thumb and an opposer of the thumb
opposition or opponent's pules think
thumb touching Pinky and so find
dexterity of the thumb like uh buttoning
Your Collar grabbing a hammer shaking a
hand and so the ination of these muscles
is by the median nerve the median nerve
courses through the carpal tunnel and
then after traversing the carpal tunnel
it sends a branch backwards called the
recurrent branch of the median nerve or
sometimes simply the recurrent median
nerve which then provides motor
inovation of the thear muscles the key
to it is the recurrent median nerve
Branch innervates the muscles after
traversing the carpal tunnel and there's
also other branches that go to the
lumbal and your digits now the
hypothenar muscles are muscles that act
on your pinky and there's three of them
abductor digiti minimi digiti minimi
means minimi small digit flexor Digi I
minimi and opponent's Digi I minimi and
so again I don't care if you can
identify these three individual muscles
on a picture or the Cav because it's a
group but it's the actions we have
muscles that will one of these muscles
will abduct the pinky one will Flex the
pinky and one will oppose pinky touching
the thumb fine movement of that small
finger and so now if we take a look at
that allner nerve as it courses into the
hand it traverses this tunnel formed by
a connective tissue attaching to the
pistoor Bone that's called gon canal and
after the aler nerve traverses gon's
Canal now enters into the hand and gives
innervation to the hypothenar muscles as
well as a bunch of other muscles in the
hand and some
skin the next group are called the
lumbal and the lumbal are forign num so
I'm going to ghost through so we can see
a little bit easier and these four
lumbal muscles arise from the flexor
digitorum profundus tendons all four of
them and then these tendons coarse up so
they arise or they originate on the the
front of the hand also called The Palmer
surface or sometimes volar surface of
the hand and then the tendons course to
the back of the digits so to best see
the insertion of these four muscles
let's take a look at a lateral view of
the digit where there's a metacarpal
there's a proximal middle and distal
fangi so between the metacarpal and
fangi is the mCP
metacarpal fenial joint and then our pip
and dip are interial joints for proximal
and
distal then we've got the same picture
except now we've overlaid muscles and
tendons so in turquoise there is a
lumbrical muscle it's arising from the
FTP tendon and then notice its
attachment is on that dark blue
structure called the extensor expansion
Hood this extensor expansion hood is is
primarily found on the dorsal surface or
posterior surface of the digits but
recognize that part of this Hood crosses
in front of the mCP joint that's going
to become significant here in a minute
so the pull of the lumle with the lumle
now contracts that first dotted Arrow
represents the vector pull and and and
see that it is in front of the mCP joint
and because of that it would cause
flection of the mCP joint in other words
lumle lumbal Flex the mCP joint point
but look at that second dotted Arrow
it's on the backside of the extensor
expansion hood on the back of the IP
joints and as a result when the lumbal
contract in addition to flexing the mCP
joint lumbal extend the IP joints this
is what makes it unique and recall that
the mCP joint extension is primarily
from the extensor digit torm communis
and the extension of the IP joints is
primarily from the lumbal this uh uh
knowledge of this will be helpful in
trying to figure out all those claw
hands that you're using and you're
studying for your
boards okay so this is a left hand this
is a light embalmed caber which means uh
the tissue doesn't fix because it's not
used with from aldhy so it can move when
you pull on muscles and this was done by
Jordan Barker um a previous student and
now Orthopedic residence so there's our
mCP joint there's the PIP and dip joints
outlined in Orange is a a lumbal that's
the first lumle muscle there's the
extensor expansion Hood starting and
then continuing on the dorsum of the
finger now I'm going to go onto this
video and watch now what happens so
there we've got tending pulling on that
Lumber comb now watch what happens to
the mCP and the IP joint flexion and
extension again one more time flexion of
the mCP extension of the IP joints
there's our
lumber now uh the interation of these
lumbal muscles is unique remember how
the fdp was funky the flexor digitorum
profundus in its interation the exact
same thing happens with these lumbal
where the median nerve after traversing
the carpal tunnel and sending a branch
to the recurrent median will then
innervate those first two lumbal going
to your index and square finger
now the olner nerve courses through
gon's canal and it interat the
hypothenar muscles it
intervesicle including the third and
fourth Lumber or the lumber that act on
the ring finger and the pinky and so if
you can remember what nerves inovate the
two bellies of the fdp you'll always
remember what nerves inovate these two
different Lumber Co
muscles next is the adductor pocis and
that it has a Traverse head and an
oblique head both of which they come
basically from that third metacarpal and
carpal bones and go to the proximal
failings of the thumb and when this
muscle contracts it will do that motion
which is thumb adduction from here to
there next is our interos muscles
there's two of them a dorsal and a
pulmer interus muscles and so in purple
we have the dorsal interus muscle and
that dot dorsal inosi muscles there's
four of them that dotted line that goes
down the swear finger shows where what
you're using as the midline for what's
considered ab and AD duction when the
dorsal and aasi muscles contract the ab
duct they pull the fingers away from the
midline in this fashion you'll notice
that I didn't show the pinky abducting
when I go from here to here because the
Pinky has its own abductor on the
hypothenar muscles and so I also put on
this page dab da because the dorsal D
inosi muscles abduct AB the metacarpal
fangel joints dab now the pulmer inosi
muscles in Orange there's three of them
and these pulmonar oi muscles are going
to adduct they pull the fingers towards
the midline the adduct the digits and so
you'll notice I put the acronym pad P
pal osus muscles will adduct the digits
hence pad and this is often why you'll
hear these neosi muscles referred to as
the pads and dabs and these muscles are
inovated by the oler Nerf
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