Sectional Anatomy The Neck The Neck

Objectives List Differentiate Identify Discuss Structures 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 sagittal, axial, and coronal planes After completing this topic, you should be able to: 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 Discuss The importance of understanding the relationships and locations between anatomic structures

Take note of each structure’s density level Sagittal Neck CT Take note of each structure’s density level Bone Tissue Spaces White Gray Black 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 (highlighted in green) has the highest atomic number of the tissues represented here. It appears white. Structures featuring dense connective tissue such as muscle, ligaments, and glands appear grey as highlighted by the blue lines. Loose connective tissue such as adipose or fat appear a darker gray. Highlighted in pink, you’ll see that the air-filled spaces, such as the sinuses, trachea and esophagus, are black.

ANATOMIC NEIGHBORHOOD Coronal Neck CT Use the relationships between each structure to find your way around the Thyroid cartilage is superior ANATOMIC NEIGHBORHOOD Cricoid cartilage is inferior This is a T1 weighted MR scan of the larynx in the coronal plane. Note that the thyroid cartilage is superior to the cricoid cartilage. How might knowing this help you view the neck in the axial plane? As you study sectional anatomy, always use the relationships between each structure to find your way around the anatomic neighborhood. 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? What is immediately posterior or anterior? What is inferior to this structure? What is superior to this structure?

The mandibular rami is a distinct structure Axial Neck CT The mandibular rami is a distinct structure Superior Inferior This image demonstrates a typical superior starting point for a scan of the neck. Notice how you can still identify the mandibular rami as distinct structures at this point. As the slices progress inferiorly into the body of the mandible, this distinction will disappear and the mandible will take on the shape of a boomerang.

Axial Neck CT Genioglossus muscle External carotid Internal carotid Internal jugular vein At approximately the level of the inferior aspect of the mandibular body, this axial image demonstrates a number of important structures. The muscle responsible for protruding the tongue, the “genioglossus” is seen clearly, as is the right external carotid, and the right internal carotid artery. Lateral to these arteries is the internal jugular vein.

Lateral Scout Image (Scan Level C2) LT Submandibular gland Epiglottis SCAN LEVEL Sternocleidomastoid Let’s look at a lateral “scout” image indicating a scan level of approximately C2. Notice where the 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. Also note the subcutaneous fat, and how it appears with greater density than the viscera. Subcutaneous fat 7

Lateral Scout Image (Scan Level C4) LT Thyroid cartilage Vocal cord Sternocleidomastoid muscle Moving more inferiorly in the neck, take a look at the C4 level. Here we continue to visualize the sternocleidomastoid muscle. And can now see the vocal cords, and thyroid cartilage. As you go from superior to inferior, notice that the shape of the neck widens. This is also apparent in axial slices. SCAN LEVEL 8

Lateral Scout Image (Scan Level C4) LT Thyroid gland Clavicle Clavicle Trachea FAT Esophagus FAT Near the base of the neck, at the approximate level of C7, you can see a clear distinction between the trachea anteriorly, and the esophagus just posterior to it. These are the two black areas on top of each other. Also well visualized is the thyroid gland. Note the clavicles just coming into view. SCAN LEVEL 9

As you study, recognizing sectional anatomy will become easier Sternocleidomastoid – C5 level Internal jugular vein – C2 level Cricoid cartilage – C6/C7 level As you study, recognizing sectional anatomy will become easier Try This at Home Look in the mirror Feel your neck Ask yourself, “Which structures are where?” Use cervical landmarks 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.

Know it in two dimensions Then try learning it in three! Make sure you know the anatomy in two dimensions. Then endeavor to learn it in three! Then try learning it in three!

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