Anatomy, Head and Neck, Adam's Apple

Article Author:
Thomas Fitzpatrick
Article Editor:
Marco Siccardi
Updated:
12/6/2018 3:46:09 PM
PubMed Link:
Anatomy, Head and Neck, Adam's Apple

Introduction

Adam’s Apple is the colloquial term used to describe what is officially named the laryngeal prominence of the thyroid cartilage. The colloquial name is thought to come from a reference to the forbidden fruit being stuck in Adam’s throat (Cobham Brewer), or just a mistranslation of the Hebrew term for the structure that is described as “the swelling of a man” (Haubrich).  In the American South, it is sometimes referred to as a goozle, playing on the verb guzzle.

It is one of the most significant external landmarks in the neck and is very useful for anatomical orientation in procedures such as cricothyroidotomies. It is notably more prominent in men than women and primarily acts to protect the vocal cords posteriorly.

Structure and Function

The thyroid cartilage is the largest of nine cartilages in the larynx. The laryngeal prominence, the Adam’s Apple specifically, is the most visible portion of this structure on the exterior and is where the two halves of cartilage meet. It has important historical, cultural, and interventional implications. It is a secondary sexual characteristic: meaning it appears around the time of puberty and helps distinguish between the sexes, as it is more prominent in men than it is in women. The swelling of the laryngeal prominence takes place during puberty and is logically thought to play a role in the voice mutation that also occurs in this period. However, no work has yet been done to prove this relationship decisively, only small reports of cadaver studies.[1]

The classic measurement of the interlaminar angle (ILA) at the level of the vocal processes is 90 degrees in the male population, and 120 in females. The broader angle in women causes it to protrudes less, not push up against the skin of the neck, and ultimately be less visible. In both sexes, regardless of the angle, the primary function of the Adam’s Apple is the same as that of the thyroid cartilage which it comprises, to protect the vocal cords immediately behind it.

Embryology

As the thyroid cartilage is connective tissue, it is a derivative of the neural crest mesenchyme of the pharyngeal arch. As with the surrounding structures in the larynx, the thyroid cartilage is an embryological derivative of both the fourth and sixth pharyngeal arches (Duke embryo).

Throughout maturity, the thyroid cartilage grows in size, descends, and becomes more cylindrical than funnel-shaped — the two lamina fuse anteriorly, except in the superior most portion, which forms the thyroid notch. The laryngeal prominence specifically starts puberty as equivalent in males and females, but the Adam’s Apple protrudes with a greater ILA and greater anterior angulation in males. Male larynges grow to be larger under the influence of differing hormone levels. During puberty, calcification of the thyroid cartilage is simultaneously occurring and does so on a spectrum throughout puberty. These calcification changes in this time are equal between males and females.[1]

Blood Supply and Lymphatics

The area surrounding the thyroid cartilage is drained by the superior laryngeal vein superiorly, as it protrudes from the thyrohyoid membrane to join the superior thyroid vein, which empties into the internal jugular, coursing up from the level of the cricothyroid membrane.

The arterial supply comes from divisions of the external carotid artery, with the superior laryngeal artery coursing superiorly, and the superior thyroid artery below. The superior laryngeal divides from the superior thyroid artery soon after it has branched off the external carotid, and before it courses inferiorly. The artery travels with the internal branch of the superior laryngeal nerve and pierces the thyrohyoid membrane.

The lymphatic drainage of this area is provided by the superior deep cervical nodes and the pretracheal nodes that drain into the superior deep cervical. The superior deep cervical chain runs underneath the sternocleidomastoid muscle along with the internal jugular vein and accessory nerve. On the left side, this merges with the thoracic duct and the brachiocephalic vein on the right.

Nerves

As the laryngeal prominence of the thyroid cartilage is a supportive, protective structure, there is no direct innervation. However, its location sits in between the internal and external branches of the superior laryngeal nerve, of the vagus (CN X). Superiorly, the internal branch pierces the thyrohyoid membrane to provide sensation to the laryngeal mucosa. Inferiorly, the external branch reaches to innervate the cricothyroid muscle.

Other important nerve structures in this region include the vagus nerve laterally, coursing down inferiorly in the carotid sheath. Also, ansa cervicalis is nearby innervating the surrounding strap muscles.

Muscles

All along the superior portion of the thyroid cartilage, the thyrohyoid membrane connects the thyroid cartilage to the hyoid bone superiorly. The laryngeal prominence itself is directly attached to the hyoid by the median thyrohyoid ligament. The thyrohyoid muscle receives innervation from CN XII and C1 and works to depress the larynx.

The infrahyoid or “strap” muscles serve to depress the hyoid bone and course anteriorly to the thyroid cartilage. These muscles obtain their nerve supply from the ansa cervicalis nerves.

Surgical Considerations

Chondrolaryngoplasty, also known as trachea (or “trach”) shave, is a purely cosmetic outpatient procedure done to reduce the girth of the Adam’s Apple. It has an excellent prognosis and is generally performed by plastic surgeons for patients who have undergone gender affirmation surgery or no longer desire to have a visible Adam’s Apple. In patients post-gender affirmation surgery, it is often performed in conjunction with a crico-thyroidopexy procedure that aims to raise the pitch of the patient’s voice.[2]

The ala, or laminae, of the thyroid cartilage, also have some use as the source for a graft in various cases. It has been used in laryngotracheoplasty to repair pediatric tracheocutaneous fistulas.[3] A recent case report showed a patient with posterior glottic stenosis effectively treated with a posterior cricoid split and thyroid ala cartilage graft.[4]

Clinical Significance

The Adam’s Apple is the most prominent, and one of the most significant laryngeal structures visible exteriorly. Its location is important in many surgical and emergency procedures, most notably in identifying the cricothyroid membrane for a cricothyroidotomy. Studies have shown this proves to be more difficult in women than in men, given the more pronounced angulation in males.

Additionally, as the Adam’s Apple is a secondary sex characteristic, its appearance is a cosmetic consideration in the transsexual community and those exploring gender affirmation/ reassignment surgery.



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