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The occipitalis, also known as the orbicularis oculi, is a muscle located in the facial area of the body. Some medical professionals prefer to consider the occipitalis a part of the occipitofrontalis muscle instead of thinking of it as a muscle on its own. The occipitalis is responsible for some facial movements, such as allowing the eyes to blink. It also aids in the ability to show expression on the face, such as raising the eyebrows or wrinkling the forehead. Another function of this muscle is to protect and moisten the eyes.
The orbital portion of the occipitalis begins on the occipital, or frontal bone, of the skull and extends over the temple and downward along the cheek. The lacrimal portion of the occipitalis muscles originates at the lacrimal bone and passes behind the lacrimal sac. The occipitalis ends in the galea aponeurotica, a tough, dense layer of fibrous tissue. The primary function is to cover and protect the upper portion of the cranium. It also allows the scalp to move over the top of the bones of the skull.
The occipitalis is the only muscle in the body capable of causing the eyes to close. If this muscle does not function properly,the eye may not close as it should. This could lead to a variety of medical concerns. In mild cases, eye drops might be required. In the most extreme cases, a complete removal of the affected eye might be necessary.
The occipitalis is considered a sphincter muscle. This means that the muscle is capable of constricting or expanding. In essence, a sphincter muscle opens and closes. This action in the occipitalis is partially voluntary and partially involuntary. Muscle movements involved in sleeping or blinking are involuntary movements, and opening or closing the eyes on purpose is completely voluntary.
When the entire occipital muscle is in use, the skin of the cheek, temple, and forehead are drawn upward. This results in the eyes being tightly shut. It is this repeated movement that leads to what is commonly known as crow's feet.
When only part of the occipitalis is being used at a given time, other muscular effects occur. For instance, parts of the occipitalis muscles are responsible for the upper eyelid being able to be raised. This action allows the front bulb of the eye to be exposed. Still other parts are responsible for allowing tears to move into the lacrimal sac, thus lubricating and moisturizing the eye. This process works much like a vacuum.