Muscle Identification - NCLEX-PN

The masseter is a quadrilateral muscle that originates from the zygomatic arch and maxilla and inserts into the coronoid process of the mandible. It's function is to lift the mandible, closing the jaw.

Mastication relies on four major muscles: the masseter, the temporalis, the medial pterygoid, and the lateral pterygoid.

The risorius is a small facial muscle that originates on the parotic fascia and inserts into the modiolus. It's primary action is to retract the corners of the mouth in smiling. The lips are pursed by the orbicularis oris. The mouth is compressed and food is kept between the teeth by the buccinator muscle. The lower lip is depressed by the depressor labii inferioris.

The orbicularis oris, a circular muscle that compresses the lips, originates on the maxilla and mandible and inserts into the skin of the lips

The depressor anguli oris is a small triangular muscle that originates on the mandible and inserts into the modiolus. It's main action is to lower the corners of the mouth in frowning. The auricular muscles are a part of the inner ear. The temporoparietalis muscle is a thin muscle covering the temporal bone, and the depressor supercilii is a muscle of the eye.

The stapedius, the smallest muscle in the human body, controls the amplitude of sound vibrations pulling on the neck of the stapes.The auriculares move the ears. The ciliary muscle and the lateral rectus are both muscles of the eye.

The genioglossus, the main muscle that protrudes the tongue, is innervated by the hypoglossal nerve, or CN XII.

The superior oblique originates on the annulus of Zinn and inserts into the outer posterior eye. It's action is to depress and internally rotate the eye.

The inferior oblique muscle of the eye, an extrinsic muscle that externally rotates and abducts the eye, has it's origin on the orbital surface of the maxilla.

The sternocleidomastoid, a long muscle that originates on the manubrium and the clavicle and inserts into the mastoid process, has several functions: when functioning unilaterally, it rotates the head, flexes the neck, and laterally flexes the neck. When functioning bilaterally, this muscle also extends the neck and is an accessory respiratory muscle.

The platysma, a sheet-like muscle that traverses the neck from the clavicle to the mouth and jaw, is innervated by the cervical branch of the facial nerve (CN VII).

The splenius capitis, one of the main extenders of the neck, has it's origin on the mastoid process of the temporal bone. The rectus capitis posterior minor, the rectus capitis posterior major, and the semispinalis capitis all originate on the nuchal line of the occipital bone.

While all of the muscles listed are part of the structure and mobility of the back, the main muscle group responsible for maintaining erect posture in the erector spinae.

The main muscle groups that make up the erector spinae are the iliocostalis muscles, the longissimus muscles, and the spinalis. The trapezius is not a part of the erector spinae group.

The frontalis muscle lifts the eyebrows and wrinkles the forehead. The brow is furrowed by the corrugator supercilii muscle, and the eye lids are raised by the levator palpebrae superioris and lowered by the orbicularis oculi.

The masseter is a quadrilateral muscle that originates from the zygomatic arch and maxilla and inserts into the coronoid process of the mandible. It's function is to lift the mandible, closing the jaw.

Mastication relies on four major muscles: the masseter, the temporalis, the medial pterygoid, and the lateral pterygoid.

The risorius is a small facial muscle that originates on the parotic fascia and inserts into the modiolus. It's primary action is to retract the corners of the mouth in smiling. The lips are pursed by the orbicularis oris. The mouth is compressed and food is kept between the teeth by the buccinator muscle. The lower lip is depressed by the depressor labii inferioris.

The orbicularis oris, a circular muscle that compresses the lips, originates on the maxilla and mandible and inserts into the skin of the lips