ANAT ch4 Muscles - Part 2

What does "suprahyoid" mean, and what is the general action of this group?

Located above the hyoid bone; they elevate the hyoid to help with swallowing.

What does "infrahyoid" mean, and what is the general action of this group?

Located below the hyoid bone; they depress the hyoid.

Describe the shape of the hyoid bone and the vertebral level where it sits.

Horseshoe shaped; at the level of the 3rd cervical vertebra.

Which four muscles make up the suprahyoid group?

Digastric (two bellies), mylohyoid, stylohyoid, and geniohyoid.

Which four muscles make up the infrahyoid group?

Sternohyoid, sternothyroid, thyrohyoid, and omohyoid.

Which suprahyoid muscles are in the anterior group?

Anterior belly of the digastric, mylohyoid, and geniohyoid.

Which suprahyoid muscles are in the posterior group?

Posterior belly of the digastric and stylohyoid.

Which suprahyoid group helps with jaw opening, and which helps with swallowing?

The anterior group helps open the jaw; both anterior and posterior groups help with swallowing.

Why does the digastric muscle have two different nerve supplies?

It has two bellies: the anterior belly is supplied by the mylohyoid nerve (CN V) and the posterior belly by the facial nerve (CN VII).

Where does the posterior belly of the digastric originate?

The mastoid notch.

Which cervical triangles is the digastric involved in forming?

The anterior cervical triangle, the submandibular triangle, and the submental triangle.

What structure does the mylohyoid form, and what is its position relative to the digastric?

The floor of the mouth; it is deep to the digastric.

Where does the mylohyoid originate?

The mylohyoid line of the mandible.

List the actions of the mylohyoid.

Elevates the hyoid, depresses the mandible, forms the floor of the mouth, and helps elevate the tongue.

What is the innervation of the mylohyoid?

The mylohyoid nerve, from CN V (trigeminal).

What is the origin, insertion, and action of the stylohyoid?

Origin: styloid process of the temporal bone. Insertion: body of the hyoid. Action: elevates the hyoid for swallowing.

What nerve supplies the stylohyoid?

The stylohyoid nerve, from CN VII (facial).

Describe the location of the geniohyoid.

It is an anterior suprahyoid muscle, deep to the mylohyoid.

What is the origin, insertion, and action of the geniohyoid?

Origin: genial tubercles of the mandible. Insertion: body of the hyoid. Action: elevates the hyoid for swallowing and depresses the jaw.

What nerve supplies the geniohyoid?

CN XII (hypoglossal).

What is the general action of the infrahyoid group?

They depress the hyoid bone.

Are the infrahyoid muscles supplied by a cranial nerve?

No; they are supplied by cervical (spinal) nerves.

What is the origin, insertion, and action of the sternohyoid?

Origin: posterior surface of the sternum. Insertion: body of the hyoid. Action: depresses the hyoid.

What is the origin, insertion, and action of the sternothyroid?

Origin: posterior surface of the sternum. Insertion: thyroid cartilage. Action: depresses the thyroid cartilage and larynx.

Which infrahyoid muscle does NOT directly depress the hyoid bone?

The sternothyroid.

What are the origin and insertion of the thyrohyoid?

Origin: thyroid cartilage. Insertion: the hyoid (body and greater cornu).

What are the actions of the thyrohyoid?

It depresses the hyoid bone and raises the thyroid cartilage and larynx.

Which muscles cover the thyrohyoid?

The omohyoid and sternohyoid.

What is unusual about the structure of the omohyoid?

It has two bellies (superior and inferior) joined by a short tendon.

Where does the inferior belly of the omohyoid originate?

The scapula.

What does the superior belly of the omohyoid divide?

The inferior part of the anterior cervical triangle into the carotid and muscular triangles.

What divides the right and left halves of the tongue?

The median septum, which corresponds to the median lingual sulcus on the dorsal surface.

What are the three regions of the tongue?

The base, the body, and the apex.

Which cranial nerve supplies all of the tongue muscles?

CN XII (hypoglossal).

What is the difference between intrinsic and extrinsic tongue muscles?

Intrinsic muscles lie entirely inside the tongue and change its shape; extrinsic muscles originate outside the tongue and insert inside it.

Name the four intrinsic tongue muscles.

Superior longitudinal, transverse, vertical, and inferior longitudinal.

What do the superior and inferior longitudinal muscles do together?

They change the tongue's shape by shortening and thickening it, and they curl it in various directions.

What do the transverse and vertical muscles do together?

They make the tongue long and narrow.

Name the three extrinsic tongue muscles and give the naming clue they share.

Genioglossus, styloglossus, and hyoglossus; all end in "glossus."

What are the origin, insertion, and actions of the genioglossus?

Origin: genial tubercles. Insertion: tongue from base to apex (a few inferior fibers on the hyoid). Actions: protrudes the tongue and depresses portions of it.

How is the genioglossus shaped, and where is it relative to the geniohyoid?

Fan shaped; it is superior to the geniohyoid.

What are the origin, insertion, and action of the styloglossus?

Origin: styloid process of the temporal bone. Insertion: lateral surface of the tongue. Action: retracts the tongue.

What are the origin, insertion, and action of the hyoglossus?

Origin: greater cornu and body of the hyoid. Insertion: lateral surface of the tongue body. Action: depresses the tongue.

Which muscle is sometimes classified as a tongue muscle but is grouped with the soft palate?

The palatoglossus.

Name the three portions of the pharynx.

Nasopharynx, oropharynx, and laryngopharynx.

What functions are the pharyngeal muscles involved in?

Speaking, swallowing, and middle ear function.

How many pharyngeal muscles are there, and how are they grouped?

Nine: one stylopharyngeus, three pharyngeal constrictors, and five soft palate muscles.

What are the origin, insertion, and action of the stylopharyngeus?

Origin: styloid process of the temporal bone. Insertion: lateral and posterior pharyngeal walls. Action: elevates and widens the pharynx.

What nerve supplies the stylopharyngeus?

CN IX (glossopharyngeal).

Name the three pharyngeal constrictors and the walls they form.

Superior, middle, and inferior; they form the lateral and posterior walls of the pharynx.

What is the origin of each pharyngeal constrictor?

Superior: pterygoid hamulus, mandible, and pterygomandibular raphe. Middle: hyoid bone and stylohyoid ligament. Inferior: thyroid and cricoid cartilages.

Where do the pharyngeal constrictors insert?

The median pharyngeal raphe, a midline fibrous band on the posterior pharyngeal wall attached to the base of the skull.

What is the action of the pharyngeal constrictors?

They raise the pharynx and larynx and drive food inferiorly into the esophagus during swallowing.

Name the five muscles of the soft palate.

Palatoglossus, palatopharyngeus, levator veli palatini, tensor veli palatini, and the muscle of the uvula.

What is the overall purpose of the soft palate muscles during swallowing?

They move the soft palate up and back to meet the posterior pharyngeal wall, separating the nasopharynx from the oral cavity so food does not enter the nasal cavity.

Which soft palate muscle is the exception to the general innervation pattern, and what nerve supplies it?

The tensor veli palatini; it is supplied by the mandibular division of the trigeminal nerve (CN V).

What are the origin, insertion, and action of the levator veli palatini?

Origin: inferior surface of the temporal bone. Insertion: palatine raphe. Action: raises the soft palate and helps close off the nasopharynx during speech and swallowing.

What are the actions of the tensor veli palatini?

It tenses and slightly lowers the soft palate, and some fibers open the auditory tube so air can flow between the pharynx and middle ear.

What are the origin and insertion of the tensor veli palatini?

Origin: auditory tube area and inferior surface of the sphenoid. Insertion: median palatine raphe.

Which structure does the palatoglossus form, and where is it?

The anterior faucial pillar, the vertical fold anterior to each palatine tonsil.

What are the origin, insertion, and actions of the palatoglossus?

Origin: median palatine raphe. Insertion: lateral surface of the tongue. Actions: elevates the base of the tongue, arches it against the soft palate, and depresses the soft palate toward the tongue.

What do the right and left palatoglossus muscles form together?

A sphincter separating the oral cavity from the pharynx.

Which structure does the palatopharyngeus form, and where is it?

The posterior faucial pillar, the vertical fold posterior to each palatine tonsil.

What are the origin, insertion, and action of the palatopharyngeus?

Origin: soft palate. Insertion: wall of the laryngopharynx and the thyroid cartilage. Action: moves the palate posteroinferiorly and the posterior pharyngeal wall anterosuperiorly to help close off the nasopharynx during swallowing.

What structure sits between the anterior and posterior faucial pillars?

The palatine tonsil.

Where does the muscle of the uvula lie, and what is its action?

Entirely within the uvula; it shortens and broadens the uvula and helps close off the nasopharynx during swallowing.