Muscles - Anatomy

The trapezius muscle is one of the superficial, upper back that originates in the spinous processes of C1-C7. Of the possible nerves, only the accessory nerve innervates muscles in the upper, superficial back. The trapezius is one of two muscles that is innervated by the accessory nerve, the other being the sternocleidomastoid.

In order for a muscle to depress and lower the thyroid cartilage, it needs to originate below and insert either at or above the thyroid cartilage. The correct answer is the sternothyroid. This muscle originates at the sternum and inserts at the thyroid cartilage. When this muscle contracts, the action causes the thyroid/larynx to lower and depress.

For this question, we are looking for a muscle that is located around the eye and thus responsible for its movement. The correct answer is the orbicularis oculi which is the only muscle of the answer choices that fits. Although each of these muscles is located in the face, none of the other choices are around the eye.

The superior oblique muscle in the upper/middle part of the eye. That means that when this muscle contracts, the eye will be pulled towards the center of the face. In anatomical position, this action is described as a medial, or towards the midline, rotation.

We are looking for a muscle around the mouth, leaving us with the risorius, orbicularis oculi, and zygomaticus minor muscles. The orbicularis oculi protrudes the lips and the zygomaticus minor elevates the upper lip. This means that the correct answer is the risorius muscle.

Of the answer choices, the risorius and master muscles control movements around the mouth and jaw. The orbicularis oculi is responsible for movement of the eyelid. This means that the correct answer is the procerus muscle.

The muscles that help in forced breathing are located in the deep compartment of the back, leaving only the serratus posterior superior and inferior muscles. The serratus posterior superior originates from C7-T3 and inserts into the superior borders of ribs 2-5, meaning it elevates the ribs while breathing. For this reason, it is the correct answer.

The oculomotor nerve is one of the cranial nerves. It runs from the brain to the orbital socket of the eye. Only two muscles in the orbital socket are not innervated by the oculomotor nerve: the superior oblique and the lateral rectus muscles. The lateral rectus is innervated by the abducens nerve (cranial nerve XI), and the superior oblique is innervated by the trochlear nerve (cranial nerve IV).

The superior oblique produces depression and intorsion of the eye. The inferior oblique produces elevation and extorsion of the eye. The lateral rectus produces abduction of the eye. The internal oblique is a trunk muscle that has no attachment to the eye, and produces (among other movements) trunk ipsilateral rotation.

The temporalis muscle closes the jaw, the deltoid is responsible for raising the arm, the orbicularis oculi closes the eye, the pectoralis major pulls the arm towards the body.

The obliquus capitis inferior muscle is innervated by the suboccipital nerve. Cranial nerve X, is also known as the vagus nerve and innervates many other muscles, including the heart, but not the obliquus capitis inferior. The trigeminal nerve is also known as cranial nerve V, is responsible for the sensations in the face.

The muscle that surrounds the opening of the mouth is known as the Obicularis Oris. The Obicularis Oclui surrounds the eye. The Masseter is connected to the mandible and responsible for chewing.The Glossus muscles are found inside the mouth and responsible for tongue movement. The Buccinator is found deep to the Masseter located on the cheek.

The hamstring muscles consist of three posterior muscles and their tendons (semitendinosus, semimembranosus, and biceps femoris). The hamstring muscles are responsible for knee flexion and hip extension. The semitendinosus, semimembranosus, and the long head of biceps femoris all originate at the ischial tuberosity (having these muscles cross the hip joint), while the short head of biceps femoris originate at the linea aspera and the lateral supracondylar line of the femur.

The flexor digitorum brevis lies in the middle of the sole of the foot above the plantar aponeurosis. It arises from a tendon from the medial process of the calcaneus, it continues towards the toes and divides into four tendons, one for each of the four lesser toes. It is innervated by the medial plantar nerve. The tibialis posterior, extensor digitorum longus, and soleus all cross the ankle joint thus having leverage above it.

The biceps femoris muscle forms part of the hamstrings, and consists of a long and short head. Both heads perform knee flexion, and the long head is involved in hip extension as it originates in the pelvis.

Quadratus femoris is a strong external rotator and adductor of the thigh. Piriformis is a lateral rotator, and laterally rotates the femur, abducting it, during hip extension. The quadriceps consist of rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. The quadriceps flex the hip and extend the knee.

The psaos major and the iliacus muscles are distinct in the abdomen and unite at the level of the inguinal ligament to form the iliopsoas muscle in the thigh. The iliopsoas muscle crosses the hip joint and inserts on to the lesser trochanter of the femur. The iliopsoas is involved in flexion and lateral rotation of the thigh. It is the strongest of the hip flexors, and is important in standing, walking, and running.

The gluteus medius, gluteus minimus, and piriformis insert onto the greater trochanter.

The biceps femoris inserts on the lateral surface of the fibular head. The other muscles of the hamstring insert of the medial surface of the tibia.

There are three auricularis muscles: the auricular anterior, the auricular superior, and the auricular posterior.

Ipsilateral rotation of the trunk at the spinal joints is an action of the internal abdominal obliques, not the rectus abdominis.