Identifying Muscles of the Trunk, Core, and Head - 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 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.

The iliofemoral ligament connects the ilium to the femur and is taut in end range hip extension (as in doing front splits) and external rotation.

Tee lateral pterygoid moves the jaw forward (protraction) and from side to side. The medial pterygoid is responsible for elevating the mandible and closing the mouth. The buccinator sucks the cheeks in towards the teeth and helps during suckling in neonates. Finally, the depressor anguli oris pulls the corners of the mouth down, as in frowning.

A spike in the concentration of luteinizing hormone (LH) leads to ovulation on day 14 of the menstrual cycle. This spike is known as the "LH surge" and is initiated by a positive feedback mechanism involving estrogen.

Follicle-stimulating hormone (FSH) is involved in the maturation of the follicle, but not ovulation. Progesterone functions in maintaining the endometrial tissue after implantation has occurred. Testosterone is not involved in the female reproductive cycle.

The zygomaticus major is a facial expression muscle that can raise the corners of the mouth during a smile. The muscle originates from the zygomatic arch and inserts in the fibrous tissue of the modiolus.

The frontalis is located within the forehead and helps raise the eyebrows. The orbicularis oris circles the mouth and helps to pucker the lips. The masseter is used to raise the mandible during mastication.

The upper fibers of the trapezius muscle elevate the scapula and raise the upper limb above the head. The trapezius muscle is innervated by the accessory nerve. Damage to the accessory nerve results in drooping of the shoulder and inability to raise the arm above the head. The deltoid muscle is also used to abduct the arm at the shoulder.

The rhomboid major serves to connect the scapula and the vertebrae, pulling the shoulders posteriorly. The levator scapulae elevates the medial angle of the scapula. The latissimus dorsi helps to adduct and extend the arm at the shoulder.

There are many structures that aid in the process of inspiration and expiration. Inspiration involves enlarging the thoracic cavity for the lungs to expand, while expiration compresses the cavity to allow carbon dioxide to leave. Inspiration will always be active, while expiration can be either passive or active. One of the most important structures for inspiration is the diaphragm. The diaphragm will contract and move downwards into the abdominal cavity, allowing the lungs to expand and draw in air. Muscles of forced expiration are the anterior abdominals, the internal intercostals, and the serratus posterior inferior muscles. They help to relax the diaphragm, which increases the abdominal pressure and pushes the ribs inwards.

The ribs are elevated and depressed by the muscles of the thoracic wall and neck. The external intercostals originate at the lower border of the ribs. With the help of the internal intercostals, they raise the ribs when inspiring. The scalene muscles of the neck work to lift the first two ribs mainly. The sternocleidomastoid muscles are attached to the sternum, and also lift upwards.

The transversus thoracis originates on the posterior part of the sternum and xiphoid, inserting into the costal cartilages of ribs 2 to 6. They pull the ribs down when expiring air.

The geniohyoid muscle is associated with the chin, as it is a muscle that is the passageway from the chin to the hyoid bone. Contraction of the geniohyoid can move the hyoid bone to further widen the airway, aiding in respiration.

The nuchal ligament is located at the back of the neck and helps maintain the vertical position of the head. The sternocleidomastoid muscles are located in the lateral portions of the neck and helps to turn the head from side to side. The iliocostalis muscles run down the back, connecting the posterior portions of the ribs; this muscle is deep to most other muscles in the back. The popliteus muscle is located poterior to the knee and helps to move the tibia posteriorly, relative to the femur.

Intercostal muscles are responsible for expanding and contracting the thoracic cavity during forced breathing. During relaxed breathing, the diaphragm is responsible for changing the volume of the thoracic cavity, driving pulmonary ventilation. Internal intercostals depress the ribs during forced exhalation and the external intercostals elevate the ribs during forced inhalation. The subscapularis is one of the rotator cuff muscles, and its function is medial rotation of the humerus.