 Hey everybody, Dr. O'Hare, in this video I just want to cover a few muscles you can really see good in these images. I really want to focus on the parts of the deltoid, but you can get a good look at the pectoralis major and latissimus dorsi as well. So pectoralis major means it's the largest muscle in the pectoral region. Think about doing a push-up. Its job is flexion, so like forward flexion here, adduction, and then medial or internal rotation. So in that push-up position, your pectoralis major has done all of those actions. Then we have the, there is a pectoralis minor, but you can't see it here. Latissimus dorsi basically means the broadest muscle on the dorsal surface, so the broadest largest muscle of your back. Latissimus dorsi is kind of cool because it's a huge muscle on your back, but it inserts on your humerus, so it moves the arm, it doesn't move the spine like the erector spiny muscle does, or do the latissimus dorsi, so it's going to extend and adduct your shoulder. So think about that as a pull-up. If you're holding onto a pull-up bar, you're going to extend your arms back and then adduct them towards your side. So a pull-up is a perfect way to use the latissimus dorsi muscle. As a little tip, the teres major muscle that's there in the shoulder also has the same function, so it kind of functions like a little latissimus dorsi. But we're going to talk about the deltoid. I've covered in other videos, but in this video I want to talk about the different parts of it. Just like the trapezius really needs to be functionally treated like an upper, middle, and lower trapezius, the deltoid needs to be treated like an anterior deltoid, middle deltoid, and posterior deltoid. So as a group, they do abduct the shoulder, and it really is only one muscle, but functionally the different parts have different jobs. The anterior deltoid is involved in abduction, but also flexion and medial rotation, because in the front of my delt contracts, it brings my arm medially. So anterior deltoid, think abduction, medial rotation, and flexion of the shoulder. The middle delt really just abduction, because it's straight out the outside and it abducks there. Then the posterior deltoid, because the muscle fibers are running in the back, is going to be abduction, lateral rotation, and extension. So there are some extra functions there. All right, so that's going to be another look at the pectoralis major and latissimus dorsi, and a deeper look there at the three parts of the deltoid, anterior, middle, and posterior. Hope this helps. Have a wonderful day. Be blessed.