Body Movements

The action of muscles results in a wide variety of body movements. Knowledge of these movements is essential to an understanding of the skeletal muscles.

Exercise 14.1

As you read the following text, perform the various motions yourself and then label the diagrams in Figure 14.1.

Flexion, Extension, and Hyperextension. In general when two bones are moved closer together from the anatomical position, the motion is flexion. Returning to the anatomical position requires extension. Hyperextension is over extension.

A special kind of flexion is dorsiflexion. This is flexion of the foot toward the ankle. Movement of the foot downward or flexion of the toes is plantar flexion (as if you were planting your toes in the ground).

Abduction and Adduction. The movement of an appendage away from the midline is abduction. Adduction returns the appendage to the anatomical position. Note that abduction must take place before adduction, just as the letter "b" comes before "d".

Rotation. Rotation is the movement of a bone or limb around its central axis. An example of rotation is the movement of the radius around the ulna. When the palm is rotated posteriorly the action is pronation. Supination is the movement of the palm to the anterior.

Circumduction. Circumduction describes the movement of a limb in such a way that the distal end makes a larger circle than the proximal end, for example the movement of a pitcher when he throws a baseball. The arms, legs, and fingers can circumduct.

Inversion and Eversion. Movement of the sole of the foot toward the midline is inversion. Movement of the sole laterally is eversion.

Elevation and Depression. The mandible and the scapulae can be moved up from their horizontal position. Such movement is elevation. Depression is the opposite of elevation.

Protraction and Retraction. The mandible and the scapulae can also be moved forward from the anatomical position. This is protraction. Retraction moves these bones back to the anatomical position.

Sphincter Action. Circular muscles such as those around the eyes and mouth are called sphincter muscles. When the muscles contract they close the opening in a sphincter action.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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