Actions
The pectoralis major has four actions which are primarily responsible for movement of the shoulder joint. The first action is flexion of the humerus, as in throwing a ball side-arm, and in lifting a child. Secondly, it adducts the humerus, as when flapping the arms. Thirdly, it rotates the humerus medially, as occurs when arm-wrestling. The pectoralis major is also responsible for keeping the arm attached to the trunk of the body. It has two different parts which are responsible for different actions. The clavicular part is close to the deltoid muscle and contributes to flexion, horizontal adduction, and inward rotation of the humerus. When at an approximately 110 degree angle, it contributes to abduction of the humerus. The sternocostal part is antagonistic to the clavicular part contributing to downward and forward movement of the arm and inward rotation when accompanied by adduction. The sternal fibers can also contribute to extension, but not beyond anatomical position.
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Famous quotes containing the word actions:
“Therefore all just persons are satisfied with their own praise. They refuse to explain themselves, and are content that new actions should do them that office. They believe that we communicate without speech, and above speech, and that no right action of ours is quite unaffecting to our friends, at whatever distance; for the influence of action is not to be measured by miles.”
—Ralph Waldo Emerson (1803–1882)
“Your toddler is no longer a baby feeling himself as part of you, using you as his controller, facilitator, his mirror for himself and the world. But he is not yet a child either; ready to see you as a person in your own right and to take responsibility for himself and his own actions in relation to you.”
—Penelope Leach (20th century)
“As soon as we exceed average human goodness by even a single step, our actions arouse suspicion. Virtue stands steadily “in the middle.””
—Friedrich Nietzsche (1844–1900)