Forearm muscles

Summary

In this anatomy lesson, students explore the muscles of the forearm and hand, focusing on flexors and extensors. The instructor guides them through identifying muscles by their origins and insertions, explaining movements like wrist flexion and finger extension. Key muscles discussed include flexor carpi radialis, flexor digitorum superficialis, and extensor carpi radialis, with a special emphasis on the complex thumb movements.

Takeaways

• 📚 This week's focus in anatomy is on the muscles of the forearm and hand, emphasizing the importance of understanding their structure and function.
• 🔍 Students are encouraged to start studying the muscles superficially and work their way deeper, examining one side of the forearm before the other.
• 💪 The forearm muscles are crucial for various hand movements, including wrist extension and flexion, finger flexion and extension, and thumb movements.
• 🤔 The key to understanding forearm muscles is to identify where the muscle originates and where it inserts, which helps in determining its function.
• 🤲 The flexor side of the forearm contains muscles that flex the wrist and fingers, such as the flexor carpi radialis, palmaris longus, and flexor carpi ulnaris.
• 👊 The extensor side of the forearm includes muscles that extend the wrist and fingers, like the extensor carpi radialis, extensor digitorum, and extensor carpi ulnaris.
• 🔗 Muscles in the forearm work together in synergy, even for simple movements like making a fist, highlighting the complexity of hand and wrist movements.
• 🔍 The flexor digitorum superficialis and flexor digitorum profundus are two layers of muscles in the forearm that flex the fingers, with the latter extending to the fingertips.
• 👂 The radial and ulnar arteries, along with the median and ulnar nerves, are important structures in the forearm that are associated with the muscles and their functions.
• 👉 The thumb has unique movements, including flexion, extension, abduction, and adduction, which are facilitated by specific muscles and tendons in the forearm.
• 🤔 The muscles of the forearm, though numerous and initially intimidating, can be more easily understood by breaking them down systematically and considering their attachments and actions.

Q & A

What are the main topics covered in the anatomy lesson discussed in the script?

The main topics covered in the anatomy lesson are the muscles of the forearm, including the flexor and extensor muscles, their functions, and how they contribute to movements such as wrist flexion, wrist extension, finger flexion, finger extension, thumb movements, and hand grip.

What is the approach suggested for studying the muscles of the forearm?

The approach suggested is to start superficially and work deep, focusing on one side of the forearm at a time. It is also recommended to consider the origin and insertion points of the muscles to understand their functions.

What are the primary functions of the muscles in the anterior (flexor) compartment of the forearm?

The primary functions of the muscles in the anterior compartment of the forearm are flexing the wrist and flexing the fingers.

What are the key muscles involved in wrist flexion and what are their names?

The key muscles involved in wrist flexion are the flexor carpi radialis, flexor carpi ulnaris, and palmaris longus.

How does the flexor digitorum superficialis muscle contribute to finger movement?

The flexor digitorum superficialis muscle contributes to finger movement by sending tendons that split to cover the middle and proximal phalanges of the fingers, allowing for flexion of the fingers.

What is the role of the flexor digitorum profundus muscle in finger movement?

The flexor digitorum profundus muscle sends tendons that run between the splitting of the flexor digitorum superficialis tendons to the very tips of the fingers, allowing for powerful grip and flexion of the fingers.

What are the primary functions of the muscles in the posterior (extensor) compartment of the forearm?

The primary functions of the muscles in the posterior compartment of the forearm are extending the wrist and extending the fingers.

What is the significance of the radial and ulnar arteries and nerves in the forearm muscles?

The radial and ulnar arteries and nerves are significant as they provide blood supply and innervation to the muscles in the forearm, which is crucial for their function.

How do the muscles of the forearm contribute to the complex movements of the hand?

The muscles of the forearm contribute to the complex movements of the hand by working together in coordinated actions. For example, muscles that flex the fingers also need to work in conjunction with muscles that extend the wrist to prevent unwanted wrist flexion during finger flexion.

What are the two main muscles involved in thumb extension and what are their names?

The two main muscles involved in thumb extension are the extensor pollicis longus and the extensor pollicis brevis.

Outlines

00:00

📚 Anatomy of Forearm Muscles

In this segment, the focus is on the muscles of the forearm and hand, specifically the flexor side. The speaker introduces the topic by discussing the muscles' roles in wrist and finger movements. They emphasize the importance of understanding the origin and insertion points of muscles to determine their function. The muscles of the forearm are categorized into flexors and extensors, with flexors being further divided into those that flex the wrist and those that flex the fingers. Key muscles mentioned include the flexor carpi radialis, flexor carpi ulnaris, and the pronator teres. The speaker also highlights the complexity of hand movements, noting that multiple muscles work together to perform simple tasks like making a fist or pointing.

05:01

💪 Deeper Exploration of Forearm Flexors

This paragraph delves deeper into the anatomy of the forearm flexors. The speaker discusses the muscles that flex the fingers, identifying the flexor digitorum superficialis and flexor digitorum profundus. They explain how these muscles have tendons that extend into the fingers, with the superficialis tendon splitting to cover the middle phalanges and the profundus tendons reaching the distal phalanges. The speaker also mentions the pronator quadratus, a muscle involved in pronation, and the importance of considering how muscles work together in the forearm to perform complex hand movements.

10:03

🤚 Extensor Muscles of the Forearm

The speaker shifts focus to the extensor muscles of the forearm, which are innervated by the radial nerve. They describe the extensor carpi radialis and extensor carpi ulnaris, which extend the wrist. The extensor digitorum muscle is highlighted as the primary muscle for extending the fingers, with a special mention of the extensor indicis, which has an additional tendon for the index finger. The speaker also discusses the role of the lateral epicondyle in the origin of these muscles and the importance of understanding the muscle's function based on its location and tendon attachments.

15:05

👍 Thumb Muscles and Movements

In this paragraph, the speaker concentrates on the muscles and movements of the thumb. They discuss the unique plane on which the thumb operates, which is at a 90-degree angle to the fingers. The speaker identifies the extensor pollicis brevis and extensor pollicis longus as key muscles involved in thumb extension, with the abductor pollicis longus and abductor pollicis brevis responsible for thumb abduction. The speaker emphasizes the complexity of thumb movements and the need to understand the specific roles of different muscles in these movements.

20:07

🧠 Simplifying Forearm Muscle Learning

The final paragraph wraps up the discussion by emphasizing the importance of breaking down the complex anatomy of the forearm muscles into manageable parts. The speaker suggests a step-by-step approach to understanding these muscles, starting from the superficial layers and working deeper. They reiterate the interconnectedness of the muscles and the need to consider how they work together to perform hand and wrist movements. The speaker concludes by acknowledging the challenge of learning these muscles but encourages a systematic approach to make the process more straightforward.

Keywords

💡Forearm

The forearm, also known as the antebrachium, is the region between the elbow and the wrist. It is a key focus of the video as it houses numerous muscles that facilitate various hand and wrist movements. In the script, the forearm is discussed in relation to its flexor and extensor muscles, which are essential for hand functions.

💡Flexor Muscles

Flexor muscles are those that facilitate the bending or flexion of a joint. In the context of the video, these muscles are primarily located in the anterior (front) compartment of the forearm and are responsible for flexing the wrist and fingers. Examples from the script include flexor carpi radialis and flexor digitorum superficialis.

💡Extensor Muscles

Extensor muscles are responsible for extending or straightening a joint. The video discusses these muscles in relation to the posterior (back) compartment of the forearm, which includes muscles that extend the wrist and fingers. Examples mentioned in the script are extensor carpi radialis and extensor digitorum.

💡Muscle Insertion

Muscle insertion refers to the point where a muscle attaches to a bone. This is crucial for understanding how muscles generate movement. In the video, the script mentions that muscles like flexor carpi radialis insert into the carpal bones and extend to the metacarpals, affecting wrist and finger movements.

💡Tendons

Tendons are the tough, inelastic cords of connective tissue that attach muscles to bones. They play a vital role in transmitting the force exerted by muscles to facilitate movement. The script describes how tendons from muscles like the flexor digitorum superficialis extend into the fingers and split to allow finger flexion.

💡Pronation

Pronation is the rotation of the forearm such that the palm faces downward. The video script mentions pronator teres and pronator quadratus as muscles involved in this movement, highlighting their importance in hand and wrist manipulation.

💡Wrist Flexion and Extension

Wrist flexion and extension are movements that bend and straighten the wrist, respectively. The video script discusses the muscles responsible for these actions, such as flexor carpi radialis for flexion and extensor carpi radialis for extension, emphasizing their role in hand functions.

💡Finger Flexion and Extension

Finger flexion and extension involve bending and straightening the fingers, respectively. The script explains how muscles like flexor digitorum superficialis and extensor digitorum are responsible for these movements, which are crucial for tasks like gripping and manipulating objects.

💡Median Nerve

The median nerve is a major nerve in the arm that provides sensation and motor function to the hand. In the video, the script mentions the median nerve in relation to its role in innervating the flexor muscles of the forearm, which is essential for hand function.

💡Radial Nerve

The radial nerve is another major nerve in the arm that provides motor function to the extensor muscles of the forearm. The video script discusses how the radial nerve innervates the extensor muscles, which are critical for wrist and finger extension.

💡Thumb Movements

The script specifically discusses the unique movements of the thumb, including flexion, extension, abduction, and adduction. These movements are facilitated by muscles like the abductor pollicis longus and extensor pollicis longus, which are crucial for the thumb's versatility in hand functions.

Highlights

Students have been studying the muscles of the forearm and the hand.

Approach the muscles of the forearm by starting superficially and working deep.

Muscle origins and insertions are key to understanding their function.

Forearm muscles are involved in wrist and finger movements.

Flexor carpi radialis is a flexor muscle of the wrist.

Palmaris longus is a muscle that forms into the palm.

Flexor carpi ulnaris is located on the ulnar side and is also a flexor of the wrist.

Pronator teres is a short muscle that causes pronation of the forearm.

Brachioradialis is a powerful flexor of the elbow.

Flexor digitorum superficialis is a broad muscle that flexes the fingers.

Flexor digitorum profundus sends tendons to the very tips of the fingers.

Pronator quadratus is a muscle that aids in pronation.

Extensor carpi radialis is an extensor muscle of the wrist on the radial side.

Extensor digitorum is the primary muscle for extending the fingers.

Extensor indicis is a muscle that extends the index finger.

Extensor carpi ulnaris is involved in wrist extension and ulnar deviation.

Abductor pollicis longus and brevis are muscles involved in thumb abduction.

Extensor pollicis brevis and longus are responsible for thumb extension.

Breaking down the forearm muscles systematically makes them easier to understand.

Transcripts

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this week in anatomy students have been

looking at the muscles of the forearm

and the hand and stuff like that so I

feel like look at this model of that arm

which happen I'm missing a whole our

whole triceps here but I'm not going to

talk about triceps so I know I'll go to

the lab see if I can find triceps find

it see you told you the students have

been studying the arm right all right

there we go got a complete model they

okay so over the next ten minutes or so

let's work our way through the muscles

of the forearm if we get really

adventurous we can look at the thumb but

you know yeah muscles are firm are scary

but we'll work it so students were

asking me how do you approach the

muscles of the forearm how do you

remember what's what so I would say

start superficially and work deep and do

one side than the other so carry on

third my name's needs clanging around in

the background I'm used he's using the

space properly I'm just pinching a bit

of space so let's look at the muscles

and then what maybe take layers off but

the main thing is when's the nos will

come from and where does it go to and I

think in the forearm if you see where

the muscle is going to that's your cue

to work out how how it works

all right so let's start on the the

flexor side so I guess we should talk

about parts of the arm right so if this

is the forearm or the antebrachium and

then the hand we've got a whole bunch of

movements of them.we so we've got

extension of the wrist which you might

also see is that's extension and then

that's flexion of the wrist to have a

bunch of muscles doing that and then

we've got flexion of the fingers an

extension of the fingers and then with

the thumb you've got to remember that

the thumb is on a plane and 90 degrees

to the fingers so you've got flexion of

the thumb and extension of the thumb and

then you've got abduction of the fingers

and adduction of the fingers and then

with the thumb you've got abduction of

the thumb and adduction of the thumb

it's commonly confused if you remember

that the thumb is on a plane and 90

degrees that the fingers all adds up

okay so the thing is whenever you're

making any movement with your hand

you've got a huge number of muscles all

working together to let you do what you

want to do even if you're just making a

fist even if you're pointing at things

because of course the muscles that are

flexing the fingers will also want to

flex the wrist so they could also flex

the wrist which means you've got to use

other muscles which extend the wrist to

stop it from flexing while you flex the

fingers so you can you know do that

right so we're gonna think maybe about

these muscles in isolation but really

you should consider that these muscles

will work together okay so let's start

with the muscles of the anterior forearm

which are going to be flexor muscles and

then either going to be flexing the

digits flexing the fingers or they're

going to be flexing the wrist so these

are the flexors all right so here's the

model is the thumb so this is a right

hand right this is the flexor

compartment this is anterior

so if if this is the thumb you know this

is the radial side and you know this is

the radial artery right so can you see

this is the radial artery here's a

tendon here and look how it's coming

from here

across here but it's only going as far

as the wrist is going to the carpal

bones so it's going to the radial side

it's going to the carpal bones and it's

a flexor so it's gonna be flexor carpi

radialis right that's this muscle here

then so the next muscle there see this

muscle here is is similar but it's more

in the middle and they've stopped here

but it's actually going to fan out so

this is going to be Palmeiras longer

there's a long muscle that's gonna form

into the palm

alright so that's

bumbum and then there's another muscle

here it's a little bit deeper but

where's this one going so this is also

going to the wrist it's going to the

carpal bones but this is on the on the

side all right this is the ulnar artery

on the nerve in here and it's also in

the flexor compartment so this must be

flexor carpi ulnaris right so there are

those three muscles there it's when I

say carpi talking about the carpals but

these these carpi muscles do actually

make it all the way to the metacarpals

but you know there's another muscle here

so you see these this muscle here short

muscle it's actually not going into the

wrist

you've got your two bones your ulnar in

the radius and this is just going across

to the radius here's the thumb here's

the radius so that short muscle is just

running across there so it's gonna pull

on the radius and cause it to do that

which is gonna make you do that so your

pronating so that's pronated terrorist

there's the cubicle faster right there's

the cubital fossa so those muscles are

all across here and then we've got this

other muscle here which is

brachioradialis all come on to in a bit

so those muscles are coming from most of

them are coming from this bony point

here here's the humerus this is the

epicondyle of the humerus and it's

medial this is the medial epicondyle of

the humerus and there what's panning

across there so that's where those wrist

flexors are coming from so if we go to

the next layer if we go a bit deeper

ones if we take these off the next layer

of muscles are going to the digits

because those are the things left over

that we want to flex and we can we can

do really strong things with our fingers

right we can make really really strong

grip so you can climb up steep cliffs

we're just holding on with our fingers

so we've got a lot of muscle in the

forearm which is running up into the

fingers so we've got these these long

tendons here now the first muscle layer

is flexor digitorum superficialis

flexors of the fingers digitorum

superficialis

so there's two layers and it's quite a

broad muscle it is again coming from

that medial epicondyle of the humerus

and it's coming from the radius and it's

extending and if we were to look in here

we owe to pull this apart we'd see four

tendons which will run underneath the

retinaculum give us these four tendons

here now the interesting thing is that

as these tenders extend into the fingers

if we have the proximal and distal

phalanges and the intermediate or middle

phalanges in between then this this

tendon of the superficial that the

flexor digitorum superficialis tendon

splits so it doesn't go to the very tips

of your fingers it goes to this part of

your finger here and it splits on either

tendon to run through

so if that's flexor digitorum

superficialis and there must be a flexor

digitorum deep or profundis meaning deep

so if i take this layer off what do I

find

all right there we go yeah so now we're

starting to see the deep nerves we've

got the median nerve here the ulnar

nerve the ulnar artery and other bits

and bobs but the muscle layer you see

how we stand to form some tendons here

so this is the muscle of flexor

digitorum profundus and it's sending

four tendons and those tendons will also

run up into the fingers and they're

going to go between the splitting of

this tendon here a megadose the very

tips of your fingers so then it's

possible to tear the tendon of flexor

digitorum profundus going to the tip of

your finger and yet still be able to

flex your finger but not be able to do

that bit not be able to do that movement

right because profundus doesn't attach

to the finger there that's most of the

muscles of the forearm you can go deeper

but you can't go deeper on this model

and if you go deeper then there's

another muscle running across here

there's another muscle running across

here and that's pronator quadratus

called rafters called rat it you know

like rectangular shaped and it's another

pronator so pronator terrors pronator

quadratus we'll both pronate so you can

pronate quite forcefully which is useful

if you're trying to you know undo bolts

or screws or things like that see it's

not so bad is it just work your way

through step-by-step so that's the

flexor compartment next is the extensor

compartment so it's these guys here so

these are all then innervated by the

radial nerve we saw the median nerve run

it through there and the medial nervous

the median nerve is in a very most of

those guys the radial nerve is

innovating the extensor muscles we've

got a few things going on here

the first thing we should talk about is

this muscle here so here is biceps right

let me put the other muscles back on so

his biceps

here's pronator teres is flexor carpi

radialis so forming the other border of

the cubital fossa was this big muscle

here and this is brachioradialis if this

is the break him up here this muscle

then is going from the brachial up to

the radius if you want to see

brachioradialis there's biceps then the

best way is to partially pronate see

your thumbs in lying with your humerus

right and then I'm gonna get the way and

then if you then try to flex your elbow

against resistance can you see this

muscle here is break here this muscle

here that pops up is brachioradialis

that then is very powerful in in flexing

in that way

it's that brachial radialis so that's

not really a forearm muscle that's where

it is but it's acting across the elbow

so we can that's not taking part in

wrist or finger movement so we can

forget about that one well don't forget

about it but so that's brachial radialis

then let's take that out of the equation

yeah

so we'll start breaking away the arles

here's the thumb so we're looking at the

right hand and we're looking at the

posterior breaky at the posterior

antebrachium the back of the forearm and

these muscles are going to be either

extending the fingers or extending the

wrist so what can we see well we've got

a muscle here and look how it's so this

is going from the other side look how

it's it's it's tendon is going look

we'll get it gets lost a bit but it

looks like this tendon is going all the

way up to the wrist and again here's the

radial artery

is on the radial side hmm so this is an

extensor muscle it's going to the wrist

so it's going to the carpal bones it's

on the radial side what do you reckon is

that extensor carpi radialis yes this is

extensor carpi radialis and by the way I

say these muscles go to the carpi the

carpals the wrist they actually insert

into the metacarpals to give that effect

but you know the trick with the flexor

carpi radialis muscle is in fact and

there are two of them

there's flexor carpi radialis longus so

then there's flexor carpi radialis

brevis there's a long one and a short

one longus is the first one you come to

so if this is brachioradialis

and this is flexor carpi radialis longus

and you can see it's longer right see

it's going all the way back here whereas

this is flexor carpi radialis brevis

flexor carpi radialis longus is coming

it's going all the way around here from

the humerus whereas ranty we've got the

we've got the lateral epicondyle and

flexor carpi radialis brevis is coming

from there there's the lateral

epicondyle there's the lateral

epicondyle of the humerus there so

brevis comes from there

whereas longus starts off back here

hence where it's that long it's what's

called longus all right what else we got

that's easy they see this muscle here

nice and wide and it carries on and

we've got all these tendons going off

here to the fingers uh-huh

so this is gonna extend the fingers so

this muscle then is extensor digitorum

that's it since it is horrible there

aren't two layers of extent there aren't

two layers it's just it's just extensor

digitorum there's no brim of those

superficialis and stuff it's just

extensor digitorum

and look at this thing here alright you

can point that you can these other

things kind of all work together I'm

gonna talk about that much but you can

do special things with this finger your

pointer finger it's got two tendons

going to it so you do have an extra

muscle here you see the tendon but the

muscle itself isn't clearly defined but

this is this muscle is extensor indices

index finger extensors indices otherwise

extensor indices and extensor digitorum

but we've got another we've got another

muscle here again we're at all up

ryan t is the lateral epicondyle yeah

the lateral epicondyle we've got a

muscle here which is then that going

into the wrist and we're on the on the

side there so then this muscle must be

extensor carpi ulnaris and am i talking

about the ease in extensor groups and

flexor groups but don't forget that the

the carpi muscle so the extensor carpi

and flexor carpi muscles on the ulnar

side will also cause all no deviation

and the extensor and flexor carpi

muscles on the radial side will cause I

can't even do it but they'll cause

radial deviation they'll bring they'll

they'll move it that way your little

fingers also a bit special here we've

got two tendons very again there's a

muscle here which is extensor digitorum

hidden by your finger extensors digit

diamond of mine so before that we've got

extender indices over here we've got

extensor did time in a mine over here

somewhere and then we've got all these

tendons which are extensor digitorum as

well coming up here so

that's pretty much it got a SUP inator

as well

we've got what antonius around here and

there's supper natus we talked about the

pronates and mussels there's also a SUP

inator which will sup relates which will

bring the hat back again but that's

really deep in here and I don't think

taking this apart will show them will

show supper major so I don't wanna talk

about the muscles of the hand there's a

whole other video yeah we really want to

talk about the thumb be really the thumb

alright so you can see lots of tendons

here going up into the thumb can't we if

we just think about the muscles of the

thumb the within the forearm now I said

that I said that last flexion of the

thumb and that's extension of the thumb

and when I extend my thumb sort of

flexion extension can you see those

tendons see those tendons that pop up

there so those tendons again involved in

extension of the thumb that's abduction

that's an option as flexion that's

extension so when I extend those two

tendons pop up the thumb gets called

pollicis it's the Pollack's so I reckon

those two tendons are path extends the

pollicis muscles and we have a short one

on a long ones we have extensor pollicis

brevis and extensor pollicis longus this

tendon here this is extensor pollicis

longus it's going down there and it's

going deep in here rather it's you know

it's coming up from that you get the

idea this tendon here is extensor

pollicis brevis i can never remember

which is which longus is down here

brevis is down here just is

yeah Carol so there's one other time

than I can see here if these two muscles

are involved in extending the thumb and

I said that this is a production you see

what I mean flexion extension flexion

extension and then this is abduction in

this direction all right you see

attending they're kind of that's this

tendon here that's what this tendons

doing these two tendons are extending

the thumb this one is a baduk thing the

thumb is taking the thumb away and there

are two abductor pollicis muscles this

one goes into the forearm so this must

be abductor pollicis longus because the

abductor pollicis brevis is within the

thumb you can find that one yourself

because I'm not doing the hand I'm doing

the forearm muscles and I see it see

he's not that bad darn I'm any I don't

have any other hand Tony no easy right

done so I'm glad a student asked me

about that this morning because I

forgotten that the muscles of the

forearm are somewhat terrifying and

there are a lot of them but if you break

them down sensibly in the way that we

just did I think they're not only a lot

more straightforward to learn but it

makes a lot more sense and you can you

can look at the muscles of the forearm

and then work out what's what I like

working out stuff much better than I

like learning stuff still learning but

anyway right see you next time

[Music]