Muscles - Anatomy

The splenius capitus muscle will be stretched most effectively by rotation of the head and neck. The splenius capitus is a broad, strap like muscle found at the posterior neck. It attaches at the base of the skull and inserts at the vertebrae of the cervical and upper thoracic spine. It is involved in head extension, in addition to lateral flexion and rotation of the cervical spine.

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 inferior oblique rotates the eye to look up and to the side. The medial rectus moves the eye to look towards the nose. The lateral rectus moves the eye to look out to the side only. The superior oblique rotates the eye to look down and out towards the side.

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 upper and lower trapezius function to upwardly rotate the scapula, as does the serratus anterior. Although the rhomboids (major and minor) can elevate the scapula, they are downward scapular rotators. Additionally, although the middle trapezius attaches to the scapula, it does not contribute to scapular upward rotation, due to the transverse orientation of its fibers.

The brachialis only produces motion across one joint; it flexes the elbow. The biceps brachii flex the shoulder and elbow and supinate the forearm. The triceps brachii extends both the shoulder and elbow. The extensor carpi radialis longus produces motion across the elbow and the wrist.

The sartorius originates from the anterior superior iliac spine (ASIS) and inserts near the tibial tuberocity, running laterally to medially along the anterior thigh. Because the sartorius crosses both the hip and the knee, contraction of the muscle is capable of flexing both the leg and thigh. By running laterally to medially, shortening of the muscle also causes lateral rotation and abduction of the thigh.

The quadriceps muscle group is primarily responsible for the extension of the knee. This group includes the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. The biceps femoris part of the hamstring muscle group and is responsible for the flexion of the knee.

The semitendinosus, gracilis, and sartorius are the three muscles that make up the pes anserine group, coming from the posterior, medial, and anterior compartments of the thigh, respectively. The adductor longus, is not part of this group as it inserts on the linea aspera of the femur, rather than the pes anserinus, like the semitendinosus, gracilis, and sartorius.

No muscles attach to the talus directly. However, the extensor digitorum brevis comes close, via its attachment to one of the talocalcaneal ligaments.

The achilles tendon or calcaneal tendon inserts on the posterior side of the calcaneus. It is the largest tendon in the body and pulls the heel up to point the toes downward. This decreases the angle between the bottom of the foot and back of the leg. This is called plantar flexion.

The soleus is the correct answer. The gastrocnemius also inserts on the calcaneus, but it originates on the condyles of the femur. Th plantaris muscle also inserts at the calcaneus, but it also originates at the femur. The biceps femoris muscles are located on the posterior side of the thigh. The sartorius originates on the anterior superior iliac spine, and inserts on the anteromedial aspect of the tibia.

We are looking for a muscle in the posterior compartment of the thigh. This means that the muscle will be on the back of the leg, between the pelvis and the kneecap. The correct answer is the gracilis muscle, which unlike the other three is located in the anterior compartment of the thigh.

The transversospinal group is made up of the multifidi, the semispinalis group, and the rotatores group. The overall action of these muscles is extension and rotation of the vertebral column. The quadratus lumborum muscle laterally flexes the vertebral column, and, when bilaterally contracted, depresses the rib cage.