Number of Origins A muscle may be named according to the number of sites to

Number of origins a muscle may be named according to

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Number of Origins - A muscle may be named according to the number of sites to which it is anchored: biceps (2), triceps (3), and quadriceps (4). Origin and Insertion- Some muscles are named for sites of attachment both at their origin and insertion. Muscle Action - The action of the muscle may be included in the name. For example, an abductor muscle moves the limb away from the midline of the body, whereas an adductor moves the limb toward the midline. In the same way, a flexor muscle causes flexion, whereas an extensor muscle straightens the limb. A levator muscle elevates a structure, and a masseter muscle enables you to chew. Muscles Head to Toe Facial Muscles Frontalis - The frontalis is a flat muscle that covers the frontal bone. It extends from the cranial aponeurosis (origin) and inserts in the skin above the eyebrows. Contraction of the muscle raises the eyebrows. Orbicularis oculi - The orbicularis oculi is a sphincter muscle that encircles the eyes. A sphincter is a ring-shaped muscle that controls the size of an opening. Contraction of the muscle closes the eye and assists in winking, blinking, and squinting. Levator palpebrae superioris - The levator palpebrae superioris muscle has its origin in the bony orbit of the eye and inserts on the upper eyelid. As its name implies, the muscle elevates the eyelid (opens the eye). Orbicularis oris- The orbicularis oris is a sphincter muscle that encircles the mouth. Contraction of this muscle assists in closing the mouth,
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forming words, and pursing the lips. It is sometimes called the kissing muscle. Buccinator- The buccinator is a muscle that has its origin on the maxilla and mandible and inserts into the orbicularis oris. The buccinator is used in actions requiring compression of the cheeks, as in sucking, whistling, and playing the trumpet. The buccinator may also be considered a chewing muscle because, on contraction, it helps position the food between the teeth for chewing. Zygomaticus - The zygomaticus is a smiling muscle; it extends from the corners of the mouth to the cheekbone (zygomatic bone). Platysma -Want to pout? The platysma is your muscle. It originates in the fascia of the shoulder and anterior chest and inserts on the mandible and tissue of the mouth and lower face. Chewing Muscles Masseter- The masseter is a muscle that has its origin on the maxilla and zygomatic process of the temporal bone and its insertion on the mandible. It acts synergistically with the temporalis muscle to close the jaw. Temporalis-The temporalis is a fan-shaped muscle that extends from the flat portion of the temporal bone (origin) to the mandible (insertion). Muscles of the Neck Sternocleidomastoid - As the name implies, the sternocleidomastoid muscle extends from the sternum and clavicle to the mastoid process of the temporal bone in the skull. Contraction of both muscles on either side of the neck causes flexion of the head. Because the head bows as if in prayer, the muscle is called the praying muscle. Contraction of only one of the sternocleidomastoid muscles causes the head to flex and to rotate toward the opposite direction.
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  • Fall '19
  • muscle weakness, muscle atrophy, functions of muscles

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