Transcript for:
MOD 8 - Understanding Hand Muscle Mechanics

so now I want to talk a little bit more on the extensive code mechanism so how the the extrinsic muscle U work with the intrinsic muscle for the h movement okay so uh if you recall that this is the extensor extensor tendon that when you pass the mCP joint it kind of join the extensor hood or extensor expansion um and then kind of continue to and split here that's the central slip and then kind of there's two Lal bands going to go to the other way and then on the on the side uh radio side there's Lumber co uh muscle and then there there is Palmer and dorsal inas kind of run through this um last week I talked briefly about how um intrinsic muscles which is the lose um has the the main role to kind of help band the mCP joint because it's originated from the fdp tendon and going to add the mCP level and it going to go dorsally and join the extensive hood and then when this muscle contract it'll it'll ex extend the IP and then um um B the mCP where um the extensor tendon is stronger at the mCP joint because uh because when it when it pass the mCP it kind of splits into Central sleep and two L bands so uh this is how U the extensor tendon and intrinsic tendon going to work on muscles and U they work together so today I want to um um Talk more about this so you kind of understand the mechanism behind that so see here you can kind of see that uh when the mCP going to go into U flexion and the line of pull from the lose and inia is going to go U to the Vol side or um the pide that would help um the muscle to pull and then you know extend the IP um joints okay so that's how um the intrinsic muscle kind of work with the extrinsic extensor so what would that look like if we don't have uh the intrinsic muscle kind of kind of working here so if we slowly looking at the extensor um tangent and then the flexor tendent on the you know on both side of the bone what we see here is um there's one exential tendon versus two flexa tendons and um the fractor tendons are really uh stronger than the extensor tendent so what I mean is when our hand is at rest you know the finger is going to is slight um slightly flexed because U the flex of are stronger and then uh it it'll pull uh the finger into more flexion than extension okay so now when we add the lumic cose and the inci into this you can kind of see that um in nature the mCP is inflection and then so the inic muscles will help of pull um the IP joint the pip and dip joint into extension so that when this person needs to um extend the finger that uh the extensor uh tendent will uh will work mainly on the mCP joint and then the inosi and the lose will will add in u act in the IP joint that can counter the pull from the flexor tendon that's how um our hand work so uh we have a term um called in intrinsic plus this is when the intrinsic muscle is uh is working or uh concentric um contraction so intrinsic plus is really U the mCP inflection and IPS in extension this is what we call uh intrinsic plus position what is intrinsic minus position you can kind of see that it's kind of totally opposite than the plus which is the mCP is in extension IP is in flexion so what I means is um if you need to stretch the intrinsic muscles you would want to put the hand into the intrinsic minus position so that you can stretch the intrinsic muscles or um when the intrinsic muscle is is not working then um a lot of uh it's it's very likely that uh our hand will go back um to this intrinsic minus position where the faor tendon are stronger and then the exter extensor tendon are kind of weaker so that they hand look like this [Music]