Sectional Anatomy Lesson 3 Topic 2: The Neck

Objectives: List structures found in the anterior and posterior regions of the neck Differentiate between tissues and structures based on displayed density levels Identify anatomy within the neck in sagittal, axial, and coronal planes Discuss the importance of understanding the relationships and locations of anatomic structures 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 anatomy within the neck in sagittal, axial, and coronal planes Discuss the importance of understanding the relationships and locations between anatomic structures

neck Midsagittal view: In the midsagittal view of the neck, you can see that the posterior region <bring in two blue lines > is comprised of the seven cervical vertebrae, along with the associated musculature and connective tissue. Anatomy in the anterior portion includes the three divisions of the pharynx: the nasopharynx <bring in top circle>; the oropharynx <bring in middle circle>; ; and the laryngopharynx <bring in bottom circle>. Additional structures include cartilage, the vocal cords, esophagus, trachea, and the submandibular and thyroid glands. Be sure to familiarize yourself with these and the other structures of the neck.

In this sagittal CT image, take note of the density level of certain structures. Recognizing which tissues and structures have greater or lesser density can help you identify specific anatomy. For example, bone, with the highest atomic number of the tissues represented here, appears white. <bring in green arrow> Structures featuring dense connective tissue such as muscle, ligaments, and glands look grey <bring in red arrow>; loose connective tissue such as adipose or “fat”, appear darker still <bring in yellow arrow>. Air filled spaces are shown as black. <bring in orange arrow>.

This image demonstrates a typical “superior” starting point for a scan of the neck. Notice how you can still identify the mandibular rami <fade 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.

Here we see a T1 weighted MR scan of the larynx in the coronal plane Here we see 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 structure 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.

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>.

I can tell you added labels—are these the things you want highlighted, or are the arrows good? LT SUBMANDIBULAR GLAND SCAN LEVEL EPIGLOTTIS Let’s look at a lateral scout image indicating a scan level of approximately C2, and correlate that with what is seen on the resulting axial slice. Here we have 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 8 8

LT SCAN LEVEL STERNOCLEIDOMASTOID MUSCLE THYROID CARTILAGE VOCAL CORD Moving more inferiorly in the neck, we look now at the C4 level. Here we continue to visualize the sternocleidomastoid muscle, and can now see the vocal cords and thyroid cartilage. Animation notes: highlight or animate terms and arrows indicating anatomy on picture on the right. As it is mentioned. 9

LT SCAN LEVEL THYROID GLAND CLAVICLE CLAVICLE FAT FAT ESOPHAGUS TRACHEA Audio: Near the base of the neck, at the approximate level of C7, we see a clear distinction between the trachea anteriorly, and the esophagus just posterior to it. Also well visualized is the thyroid gland. Note the clavicles just coming into view. Animation notes: Again, if possible please bring in the arrows and terms as each is mentioned. 10

Sternocleidomastoid – C5 level Internal jugular vein – C2 level Do you want the labels below each image brought in? Audio: 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