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 orbicularis oculi closes the eyes. It originates from the frontal and lacrimal bones, and from the medial palpebral ligament, which is attached to the frontal process of the maxilla and inserts into the lateral palpebral raphe. The buccinator pulls the cheeks into the teeth, The procerus wrinkles the nose. The depressor labii inferioris pulls the lower lip down.

The nasalis widens the opening of the nose by compressing the nasal cartilages, flaring out the nostrils. The frontalis wrinkles the forehead while the procerus wrinkles the nose. The levator anguli oris raises the corners of the mouth.

The platsyma muscle is responsible for both wrinkling the skin of the neck and pulling the lower lip down. The platysma is superficial to the sternocleidomastoid, originates from the clavicle, and inserts onto the base of the mandible and the skin of the cheek, lower lip and lower mouth. The depressor labii inferioris only pulls down the lower lip. The depressor anguli oris pulls the corners of the mouth down, while the risorius pulls the sides of the mouth into a grimace.

The masseter muscle, one of the strongest in the body, is the main muscle of chewing (mastication). The temporalis muscle moves the mandible up and backwards. The mandible is the jaw bone. The lateral pterygoid muscle is involved in mastication, but is not the strongest.

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.

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 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 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.

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.