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Head and Neck

Table III-6-4. Skeletal Muscles Innervated by Cranial Nerves (continued)

Muscles Derived From a

Pharyngeal Arch

Cranial Nerve

Muscles

Skeletal Elements

3rd arch (IX innervates only

Glossopharyngeal (IX)

Stylopharyngeus

Hyoid (inferior part)

one muscle, the

stylopharyngeus)

4 th arch

Vagus (X) superior laryngeal

Cricothyroid

Thyroid cartilage

(external branch)

-Inferior constrietor

Muscles of palate and pharynx

Vagus (X) pharyngeal

(controversial origin)

branches to pharyngeal

Levator veli palatini

(pharyngeal branches of X

plexus

Uvular muscle

innervate all muscles of palate

Superior/ middle

except tensor veU palatini)

constrictors

(pharyngeal branches of X

Salpingopharyngeus

innervate all muscles of

Palatoglossus

pharynx except

Palato p h arynge us

stylopharyngeus and inferior

constrictor)

! 5th arch

Lost

6th arch (recurrent laryngeal

Vagus (X) recurrent

Lateral cricoarytenoid

Cricoid, arytenoid,

of X innervates all intrinsic

laryngeal

Posterior cricoarytenoid

corniculate, cuneiform

muscles of larynx except

Transverse arytenoid

cartilages

cricothyroid)

Oblique arytenoid

Thyroarytenoid (vocalis)

Aryepiglottics

Inferior constrictor

Muscles of myotome origin

Accessory (XI)

Trapezius

Scapula

(XI innervates two muscles that

Sternocleidomastoid

Skull

shrug shoulder or turn head)

Occipital myotome muscles

Hypoglossal (XII)

Genioglossus

(XII innervates all tongue

Hyo gloss us

muscles ending in -glossus

Styloglossus

except palatoglossus)

Preotic myotome muscles (III

Oculomotor (III)

Superior, inferior, and

innervates all muscles that

medial rectus; inferior

move the eyeball except

oblique, levator palpebrae

superior oblique and lateral

superioris

rectus)

Trochlear (IV)

Superior oblique

Abducens (VI)

Lateral rectus

Sinus

Dens

Mandible

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Dens

Frontal

Sinus

Mandible

Copyright 2000 Gold Standard Multimedia, Inc. Alt rights reserved.

Figure III-6-18. Head and Neck: Posteroanterior View of Skull

Pituitary Gland

Sphenoid Frontal Sinus Sinus

Maxillary Sinus

Pituitary Gland

Sphenoid Frontal Sinus Sinus

Maxillary Sinus

Figure NI-6-19. Head and Neck: Lateral Skull

Nasal Ethmoid Septum Air Cell

Middle Optic Cranial Canal Fossa

Medial View Rights Eyeball

Figure 111-6-22. Head and Neck: CT, Skull

Nasal Ethmoid Septum Air Cell

Middle Optic Cranial Canal Fossa

Figure 111-6-22. Head and Neck: CT, Skull

Medial Optic Lateral Rectus Nerve Rectus

Sphenoid Pituitary Posterior

Sinus Fossa Clinoid

Medial Optic Lateral Rectus Nerve Rectus

Sphenoid Pituitary Posterior

Sinus Fossa Clinoid

Figure IM-6-23. Head and Neck: CT, Orbit

Figure 111-6-25. Head and

Neck: CT, Neck at C3

Figure 111-6-25. Head and

Neck: CT, Neck at C3

Thyroid Gland

Thyroid Gland

Common Internal External

Carotid Artery Jugular Vein Jugular Vein

Figure 111-6-26. Head and Neck: CT, Neck at C5

Common Internal External

Carotid Artery Jugular Vein Jugular Vein

Figure 111-6-26. Head and Neck: CT, Neck at C5

Chapter Summary

The neck is divided by the sternocleidomastoid muscle into an anterior and posterior triangle. The anterior triangle contains vascular structures (carotid artery and internal jugular vein), cranial nerve X and the respiratory (trachea and larynx) and digestive (pharynx and esophagus) visceral structures. The posterior triangle contains the muscles associated with the cervical vertebrae, cranial nerve XI, cervical plexus, and the origins of the brachial plexus.

Many structures of the head and neck develop from the branchial (pharyngeal) apparatus. The apparatus consists of pharyngeal arches, pouches, and grooves, The grooves are composed of ectoderm, the pouches are composed of endoderm, and the arches are composed of mesoderm and neural crest cells. The adult derivatives of the arches and pouches are given in Tables 111-6-1 and 111-6-2, respectively.

The anterior two-thirds of the tongue develops from the first pharyngeal arch, and the posterior one-third develops from the third pharyngeal arch. The muscles of the tongue derive from myoblasts that migrate into the head from the occipital somites and are innervated by cranial nerve XII.

The face develops from five structures derived from the first pharyngeal arch: frontonasal prominence, a pair of maxillary prominences, and a pair of mandibular prominences. The mandibular prominences form the lower jaw, the frontonasal prominence forms the forehead, and the maxillary prominences j form the cheek, lateral upper lip, and the secondary palate. The midline of the upper lip, the nasal j septum, and the primary palate are formed by the medial nasal prominence. The primary and I secondary palate fuse to form the definite palate.

(Continued)

Chapter Summary (continued)

The floor of the cranial cavity is divided into the anterior, middle, and posterior cranial fossae. The openings in the skull provide for passage of the cranial nerves and blood vessels. These are listed in Figures 111-6-11 and MI-6-15.

Venous return from the brain and other structures of the cranial vault is provided by the dural venous sinuses, which ultimately drain into the internal jugular vein at the jugular foramen. Most of these sinuses are located in the folds of the dura mater (falx cerebri and tentorium cerebelli). The major ones are the superior and inferior sagittal and the transverse, sigmoid, and cavernous sinuses. The cavernous sinus is significant because cranial nerves III and IV and the ophthalmic and maxillary divisions of cranial nerve V course in the lateral wall of the cavernous sinus, and the internal carotid artery and cranial nerve VI are found in the lumen.

The orbit contains the ocular muscles, eyeball, and transmits the optic nerve and ophthalmic artery. CN VI innervates the lateral rectus muscle, CN IV innervates the superior oblique muscle, and the remaining muscles are innervated by CN III. The ciliary muscle of accommodation and the sphincter pupillae are supplied by the parasympathetic fibers of CN III, white the dilator pupillae muscle receives sympathetic innervations.

The infratemporal fossa contains the muscles of mastication, distributions of the mandibular nerve and maxillary artery, the otic ganglion, and the chorda tympani.

The pharynx is the fibromuscular tube that is divided into three parts and serves both respiratory and digestive functions. The sensory supply for the three parts are CN IX from the nasopharynx and oropharynx and CN X from the laryngopharynx. Motor innervation is provided by CN X to five muscles of the pharynx and CN IX to the stylopharyngeus muscle. These sensory and motor innervations provide the basis of the cough and gag reflexes.

The muscles and the cartilages of the larynx serve both respiratory and phonation functions. Two branches (recurrent laryngeal and superior laryngeal nerves) of CN X innervate the muscles of the larynx and are sensory from the laryngeal mucosa of the vestibule, ventricle, and infraglottic cavity.

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