Anatomy clinical correlates: Viscera of the neck

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Introduction0:00–0:36

The neck houses a number of important anatomical structures and serves as the gateway between our head and body. These structures include major blood vessels and nerves, parts of the respiratory and digestive tract, as well as important endocrine glands such as the thyroid and parathyroid glands.
However, the neck is very exposed and vulnerable to injury, and all of these important structures in the neck are susceptible to a variety of clinical conditions.
So take a quick moment, stretch out your neck, and let's get started!Let's begin with the thyroid gland. When there is abnormal growth of the thyroid gland, it is called a goiter.

Goiter0:36–1:47

When the gland gets big enough, it can be seen as a bulge in the lower part of the neck, and may even extend deep to the sternum.
Causes of a goiter include iodine deficiency, autoimmune disorders such as Hashimoto’s thyroiditis and Graves disease, thyroid cancer, or a thyroid cyst.
The thyroid gland can enlarge anteriorly, posteriorly, inferiorly, laterally, or even substernally, but it won't enlarge superiorly because of the superior attachments of the overlying sternothyroid and sternohyoid muscles.
If it enlarges, it has the potential to compress nearby structures such as the trachea, causing difficulty breathing; the esophagus, leading to difficulty swallowing; the recurrent laryngeal nerves, leading to hoarseness; as well as the jugular veins, leading to thrombosis and superior vena cava syndrome in rare cases.
Another condition that causes swelling of the neck is a thyroglossal duct cyst, which is the most common congenital cyst in the neck.

Thyroglossal duct cyst1:47–3:16

This condition occurs because during development, the thyroid gland actually develops in the floor of the embryonic pharynx in a small area identified as the foramen cecum which is found on the dorsum of the tongue.
During development, the thyroid gland migrates from the tongue into the neck passing anterior to the hyoid bone through the thyroglossal duct.
This duct attaches the developing thyroid gland to the foramen cecum and normally disappears after birth, however, sometimes parts of this duct remain, and a thyroglossal duct cyst can form along any part of it.This cyst is usually located along the midline of the anterior neck, close or just inferior to the hyoid bone, and can form a visual and palpable mass.
Most cysts are asymptomatic, but sometimes they can cause neck pain and dysphagia. Other complications include infections or rupture, where rupture can lead to a thyroglossal fistula.
In rare cases, a thyroglossal duct cyst carcinoma can develop from the ectopic thyroid tissue within the cyst. Clinically, the neck mass will move with swallowing or tongue protrusion as the duct is tethered to the tongue, which is the way to distinguish it from other neck swellings.
Now, when a tumor of the thyroid is diagnosed, partial surgical removal of the gland called a partial thyroidectomy, or complete removal called a thyroidectomy, is required.

Thyroidectomy3:16–5:15

However during a thyroidectomy, caution is needed in order to prevent damage to other important surrounding structures. For example, sometimes the parathyroid glands can also be removed during a thyroidectomy due to their small size and variable location within the thyroid gland, particularly the inferior parathyroid glands.
Removal of the parathyroid glands will lead to hypoparathyroidism and can result in tetany, which is a severe neurologic syndrome caused by low calcium levels in the blood due to the decrease in parathyroid hormone.
This manifests as muscle twitches, cramps, and contractions, and sometimes can even progress to death if the laryngeal and respiratory muscles are involved.
To prevent removal of the parathyroid glands during a thyroidectomy, surgeons usually preserve the posterior part of the lobes of the thyroid gland.
If that’s not possible, the parathyroid glands are carefully isolated with their blood vessels intact, and can be transplanted back into the body, for example into the arm so they won’t be damaged by subsequent thyroid surgery or radiation therapy.
Also remember, during a thyroidectomy a few other structures can be damaged as well. The recurrent laryngeal nerves run near the inferior pole of the thyroid gland and pass near the inferior thyroid artery, which needs to be ligated and cut, as well as the the external branch of the superior laryngeal nerve, which may be damaged, during removal of the superior portions of the thyroid gland.
Ok then! Now let’s switch gears and look at the larynx, which is responsible for voice production and maintaining a patent airway.

Larynx5:15–6:33

The larynx contains the vocal cords and the rima glottidis which are responsible for voice production. In fact, the pitch of the voice is changed by variations in the tension and length of the vocal folds, the width of the rima glottidis, and the intensity of the expiratory effort.
However one of the greatest changes to the larynx occurs during puberty. During puberty in biological males, the increased production of testosterone strengthens the walls of the larynx and enlarges the laryngeal cavity, where in biological females the size of the larynx only slightly increases.
Furthermore in biological males, the laryngeal cartilages enlarge and the laryngeal prominence becomes more apparent. The anteroposterior diameter of the rima glottidis almost doubles its size and the vocal folds become longer and thicker.
This is the reason why the voice in biological males typically becomes lower pitch after puberty - and why there’s that awkward transition stage while the anatomy of the larynx matures during puberty!So can you recall a few causes of a neck mass?

Quiz6:33–6:47

How about the structures damaged during a thyroidectomy? Let's talk a bit more about the larynx.

Laryngoscopy6:47–8:24

Now, everyone loves to hear someone who is good at singing, but have you ever wanted to take a look at their vocal cords to see what makes them an amazing singer?
Or maybe take a look at what makes your friend who never stops singing a bad singer? Ok, looking at the vocal cords might not tell us what makes a good singer, but visualizing the larynx can help us identify a variety of clinical conditions.
To look at the larynx a laryngoscopy can be performed, which is a procedure that helps visualize the interior of the larynx.
This can be done under direct laryngoscopy, when the larynx is examined with a tubular endoscopic instrument, called a laryngoscope.
Laryngoscopy is indicated in many clinical scenarios. It may be needed in acute scenarios during respiratory compromise in order to facilitate tracheal intubation, or intubation during general anesthesia.
It can also be used to visualize the larynx if cancer is suspected, or visualize the vocal cords to investigate vocal cord pathology such as polyps or paralysis.
Taking a look at this laryngoscopy image of the larynx, we can identity the piriform fossa, the cricoid cartilage which is covered in a layer of mucosa, the aryepiglottic fold, the vocal folds, the rima glottidis, the quadrangular membrane which is also covered in a layer of mucosa, the vestibular folds, the epiglottis, the median glossoepiglottic ligament, the valleculae, and the dorsum of the tongue.
Now, I am sure you have seen a movie where someone accidentally inhales their food down the wrong tube and frantically needs the Heimlich maneuver.

Laryngeal obstruction8:24–10:05

This is an example of a foreign object being accidentally inhaled into the airways, in which case it goes through the laryngeal inlet into the vestibule of the larynx, and can become trapped superior to the vestibular folds.
This causes the laryngeal muscles to spasm, tensing the vocal folds. The vocal folds can then close off the rima glottidis so air cannot enter into the trachea, causing laryngeal obstruction, choking, and eventual asphyxiation if the obstruction is not removed.
Now, the vestibular folds are part of the protective mechanism of the larynx, so when foreign objects, such as food, come in contact with the vestibular mucosa, violent coughing occurs in an attempt to eject the object from the larynx.
If coughing doesn’t eject the foreign object, urgent help must be given to remove the object and open the airway. One important measure is to give the Heimlich maneuver, which consists of a sudden compression of the abdomen that causes the diaphragm to elevate and compress the lungs.
The lungs will still contain air, so compressing the diaphragm upwards will expel air from the lungs through the trachea and larynx, creating a backflow of pressure that usually dislodges the foreign object.In extreme cases, when the Heimlich maneuver fails, other procedures must be considered to get air into the lungs, such as a cricothyrotomy or a tracheostomy.
A cricothyrotomy is a procedure that can be performed in both emergency and controlled surgical situations. Emergency cricothyrotomy involves the insertion of a large bore needle through the cricothyroid ligament to permit fast entry of air into the trachea, and is typically indicated in situations such as laryngeal edema due to anaphylactic reactions, massive hemorrhage, trauma, and any other upper airway obstruction which can quickly progress to airway obstruction and compromise.

Cricothyrotomy10:05–11:19

The reason a cricothyrotomy is preferred in emergency situations is because the cricothyroid ligament is easily palpated, as it attaches the thyroid cartilage above to the cricoid cartilage below, and can be felt by palpating a soft spot inferior to the laryngeal prominence of the thyroid cartilage and above the cricoid cartilage.
However, emergency cricothyrotomy is only a temporary measure until a definitive airway can be established, which can be done with a surgical cricothyrotomy done under controlled conditions where a tracheostomy tube is placed into the trachea through the incision.
Another type of airway that can be established is a procedure called a tracheostomy, which is indicated in individuals with an upper airway obstruction or respiratory failure, and are preferred in situations that may require prolonged tube placement.

Tracheostomy11:19–11:57

A tracheostomy involves an incision through the skin of the neck and the anterior wall of the trachea. From here, an opening is made in the anterior wall of the trachea between the first and second tracheal rings, or anywhere through the second to fourth tracheal rings.
This procedure establishes a patent airway, allowing the person to breathe without using the nose or the mouth. Finally, let’s quickly discuss what a Zenker diverticulum is.

Zenker diverticulum11:57–13:04

A Zenker diverticulum describes a posterior outpouching of herniated esophageal mucosa through an area of muscle weakness on the posterior esophageal wall.
A Zenker diverticulum is typically found in an area called the Killian triangle, which is a focal weakness in the hypopharynx between the thyropharyngeus and cricopharyngeus parts of the inferior pharyngeal constrictor muscle, leading to a pseudo or false diverticulum where food and liquids can become trapped.
The best way to visualize this condition is through an upper gastrointestinal contrast study as seen here. In most cases, a Zenker diverticulum is asymptomatic, but it should be suspected in individuals who present with progressive dysphagia, regurgitation, cough, aspiration, and foul smelling breath, called halitosis, due to food getting trapped in this outpouching of esophageal mucosa.Alright, as a quick recap.

Review13:04–14:51

A goiter refers to the swelling of the thyroid gland, which can be caused by iodine deficiency and autoimmune diseases like Hashimoto thyroiditis and Graves disease.
A thyroglossal duct cyst is another cause of neck swelling, and is typically found in the anterior midline portion of the neck near the hyoid bone.
Surgical removal of the thyroid gland is called a thyroidectomy, and during this procedure the removal of the parathyroid glands can be done by mistake causing tetany.
A laryngoscopy can be performed to identify the cause of several issues involving the larynx, such as voice problems, throat pain, hoarseness, difficulty swallowing, or obstructive masses in the airway.
Laryngeal obstruction can be caused by a foreign object that is accidentally inhaled into the airways which can lead to asphyxiation if the object is not removed.
In order to open the airway, emergency measures must be taken, such as the Heimlich maneuver. If the Heimlich maneuver fails, other procedures must be considered, such as cricothyrotomy or tracheostomy.
Cricothyrotomy can be done in emergency situations for airway access as the cricothyroid ligament is easily palpated, where tracheostomy can also be done to maintain a patent airway and is preferred in situations that require prolonged tube placement.A Zenker diverticulum is a posterior outpouching of the esophageal mucosa through a weakened area of the inferior pharyngeal constrictor muscle, and is an area where food and liquids can become trapped leading to difficulty swallowing.