Материал: Kaplan USMLE-1 (2013) - Anatomy

Chapter 6 • Head and Neck

ChapterSummary

•The neck is divided by the sternocleidomastoid muscle into an anterior and posterior triangle. The anterior triangle contains vascular structures (carotid artery and internal jugularvein), cranial nerve (CN) 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, CN XI, cervical plexus, and the origins ofthe brachia[ 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 ofthe arches and pouches are given in Tables 111-6-1 and 111-6-2, respectively.

•The anterior 2/3 of the tongue develops from the first pharyngeal arch, and the posterior 1/3 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 CN XII.

•The face develops from 5 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 form the cheek, lateral upper lip, and the secondary palate. The mid line of the upper lip, the nasal septum, and the primary palate are formed by the medial nasal prominence. The primary and secondary palate fuse to form the definite palate.

•The floor ofthe cranial cavity is divided into the anterior, middle, and posterior cranial fossae. The openings in the skull provide for passage ofthe cranial nerves and blood vessels. These are listed in Figures 111-6-8 and 111-6-9.

•Venous return from the brain and other structures ofthe cranial vault is provided by the dural venous sinuses, which ultimately drain into the internal jugularvein at the jugular foramen. Most ofthese sinuses are located in

the folds ofthe 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 CN Ill and IV and the ophthalmic and maxillary divisions of CN V course in the lateral wall ofthe cavernous sinus, and the internal carotid artery and CN 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 Ill.

MEDICAL 329