Latissimus dorsi
The muscle you are referring to is the subscapularis muscle. It originates on the subscapular fossa of the scapula and inserts on the lesser tubercle of the humerus. It is responsible for medial rotation of the shoulder joint.
The rotator cuff muscles are referred to occasionally as the SITS muscles. The Supraspinatus, Infraspinatus, Teres minor and the subscapularis. The Supras. originates on the scapula and inserts on the humerus. The Infras. originates on the scapula and inserts on the humerus(greater tubercle. The Teres minor originates on the scapula and inserts on the humerus. The Subscapularis originates on the scapula and inserts on the humerus(lesser tubercle). The function of this muscle group is to stabilize the shoulder joint. Hope this helps.
The triceps originates on the scapula and proximal humerus and inserts on the olecranon process. The muscles has three heads (hence its name) so it has multiple origins.
The biceps brachii muscle.
The brachialis muscle originates on the distal anterior humerus and insert at the coronoid process. The function of the brachialis is flexion at the elbow.
The large broad sheet of muscle you are referring to is the latissimus dorsi. It is responsible for movements like shoulder extension, adduction, and medial rotation of the arm.
You have the pectoralis major muscle in the chest wall. It arise from the sternum and the clavicle. It is inserted on the lateral part of the bicipital groove.
The rhomboid major originates on the spinous processes of the second to fifth thoracic border and inserts on the medial border of the scapula. It retracts the scapula.
The latissimus dorsi comes from the spinous processes of the seventh to twelfth thoracic vertebrae, inferior three or four ribs, and the scapula. It inserts into the humerus.
olecranon fossa
supraspinatus
It inserts onto the humerus. It originates from the coracoid process of the scapula. There are 2 parts - Long head and short head. The long head is connected to the coracoid process by a tendon that comes up between the tubercules of the humerous. The short head is connected directly to the humerus.