Sectional Anatomy Lesson 3 Topic 2: The Neck

After completing this topic you should: List structures found in the anterior and posterior regions of the neck Differentiate between tissues and structures based on displayed density levels Identify various anatomy within the neck in sagittal, axial, and coronal planes Discuss the importance of understanding the relationships and locations between anatomic structures Audio: read slide objectives

Sagittal In this sagittal CT image, take note of the density level of the different structures. Recognizing which tissues and structures have greater or lesser density can help you identify specific anatomy. For example, bone,<bring in green arrows> with the highest atomic number of the tissues represented here, appears white Structures featuring dense connective tissue such as muscle, ligaments, and glands appear grey<bring in blue arrows> Loose connective tissue such as adipose or fat appear darker still. Air filled spaces, such as the sinuses, trachea and esophagus in this image look black <bring in yellow arrows> .

Axial CT This image demonstrates a typical superior starting point for a scan of the neck. Notice how you can still identify the mandibular rami <bring in red arrows> as distinct structures at this point. As the slices progress inferiorly into the body of the mandible, this distinction will disappear, <fade in second image> and the mandible will take on the shape of a boomerang <superimpose boomerang over white shape at top of second image>.

Coronal CT This is a T1 weighted MR scan of the larynx, in the coronal plane. Note that the thyroid cartilage <bring in red arrow> is superior to the cricoid cartilage <bring in blue arrow> How might knowing this help you view the neck in the axial plane? As you study sectional anatomy, always try to think about the relationship one structures has with another. Once you learn which structures are in a particular region, cavity, or quadrant, ask yourself: what is superior to this structure? What is inferior to that structure? What is immediately posterior to this, or anterior to that? Sectional anatomy is all about knowing your way around the anatomic neighborhood.

Audio: This axial image, at approximately the level of the inferior aspect of the mandibular body, demonstrates a number of important structures. The muscle responsible for protruding the tongue, the “genioglossus” (bring in red arrow) is seen clearly, as is the right external carotid (bring in green arrow), and the right internal carotid artery (bring in yellow arrow). Lateral to these arteries is the internal jugular vein (highlight existing line with blue arrow).

LT 7 SUBMANDIBULAR GLAND SCAN LEVEL EPIGLOTTIS Audio: Let’s look at a lateral “scout” image indicating a scan level of approximately C2. Notice where the yellow line is on the scout image so you can correlate that with what is seen on the resulting axial slice. Some important anatomy to notice is the epiglottis, the submandibular glands, and the sternocleidomastoid muscle (fade in illustration of muscle). Also note the subcutaneous fat, and how it appears with greater density than the viscera. Other animation notes: If possible highlight each structure as it is mentioned STERNOCLEIDOMASTOID MUSCLE SUBCUTANEOUS FAT 7 7

LT SCAN LEVEL STERNOCLEIDOMASTOID MUSCLE THYROID CARTILAGE VOCAL CORD Moving more inferiorly in the neck, take a look at the C4 level. Here we continue to visualize the sternocleidomastoid muscle <highlight term and arrow>, and can now see the vocal cords <highlight term and arrow>, and thyroid cartilage <highlight term and arrow>, . Notice also in the axial slices, as you go from superior to inferior the shape of the neck widens. 8

LT SCAN LEVEL THYROID GLAND CLAVICLE CLAVICLE FAT FAT ESOPHAGUS TRACHEA Near the base of the neck, at the approximate level of C7, you can see a clear distinction between the trachea anteriorly <highlight term and arrow> , and the esophagus <highlight term and arrow> just posterior to it. These are the two black areas on top of each other. Also well visualized is the thyroid gland <highlight term and arrow> . Note the clavicles just coming into view <highlight term and arrow>, . 9

Sternocleidomastoid – C5 level Internal jugular vein – C2 level As you continue to carefully study the different resources available to you, including your text, workbook, and various websites, recognizing sectional anatomy will become easier. Try this exercise the next time you look in the mirror: take notice of your neck; feel different areas with your fingers and ask yourself “which structures are where?” As you look at and feel your own neck, try to visualize and name where key structures are. Use cervical landmarks for reference, it is a helpful starting point. Animation notes: slowly fade in labels (not arrows) as narration occurs. Cricoid cartilage – C6/C7 level

End of Topic Two Video Make sure you know it in two dimensions; then endeavor to learn it in three! Audio: read slide