question for physical therapists or others that know about muscles!

[cepmom]

May be a long shot, but thought I throw this out there....ok, I've been googling and reading my A&P book over and over but can't find the answer to this question...explain how latissimus dorsi aids in medial, not lateral rotation. I'm thinking it has to do with the way the muscle twists and attaches to the humerus that allows it to rotate medially and not laterally but I wanted to confirm that. Anyone??

 

[AshleyW]

May be a long shot, but thought I throw this out there....ok, I've been googling and reading my A&P book over and over but can't find the answer to this question...explain how latissimus dorsi aids in medial, not lateral rotation. I'm thinking it has to do with the way the muscle twists and attaches to the humerus that allows it to rotate medially and not laterally but I wanted to confirm that. Anyone??

Yep, it's because of how it attaches to the humerus. It attaches to the medial side of the humerus, so when the muscle contracts, it pulls on the inside of the arm, turning it medially. If it attached to the lateral side of the humerus, then it would rotate the arm laterally when it contracted. If the latissimus dorsi [where its actually located] were to aid in lateral rotation, the muscle would have to "push" on the arm where it connects - which isn't very feasible.

Hopefully I didn't just make that more confusing than it had to be, because it sounds like you had the right answer in the first place.

 

[cepmom]

Yep, it's because of how it attaches to the humerus. It attaches to the medial side of the humerus, so when the muscle contracts, it pulls on the inside of the arm, turning it medially. If it attached to the lateral side of the humerus, then it would rotate the arm laterally when it contracted. If the latissimus dorsi [where its actually located] were to aid in lateral rotation, the muscle would have to "push" on the arm where it connects - which isn't very feasible.

Hopefully I didn't just make that more confusing than it had to be, because it sounds like you had the right answer in the first place.

you are awesome! thank you! I kept thinking that was the reason but wanted to be sure I wasn't missing something. Does the fact that it twists back on itself before insertion have anything to do with it or simply that it inserts on the medial side of the humerus?