The larynx is an organ that is part of the upper respiratory tract. It is a cavity surrounded by cartilage. The larynx is located above the trachea at the level of the fourth, fifth and sixth cervical vertebrae. But it is not permanently static at this level. When swallowing and pronouncing sounds, it shifts up or down. Read more about the structure, innervation and blood supply of the larynx later in the article.
Location of the larynx
Before we turn to the consideration of the blood vessels and innervation of the larynx, you should figure out where it is generally located, as well as what cartilage and muscles form it. This is really important, since the vessels and nerves are necessary for the nutrition of these muscles and cartilage.
The larynx can be well palpated, as it is located superficially, almost immediately under the skin. And some protrusions are visible to the naked eye. They serve as anatomical landmarks forperforming a tracheostomy. In men, the Adam's apple is well visualized, which is actually a protrusion of the thyroid cartilage. In girls and children, you can see the arch of the cricoid cartilage.
The upper border of the larynx is an opening, which is called the entrance to the larynx. From below, the larynx smoothly passes into the trachea - the breathing tube. On the sides of it are the lobes of the thyroid gland, as well as the vessels and nerves of the neck.
Cartilaginous skeleton
The study of the innervation of the larynx becomes easier if you know the cartilage that is part of it. After all, the name of the nerve often corresponds to the name of the cartilage.
The main cartilage of the larynx is called the cricoid. From the front it forms an arc, and from the back it looks like a quadrangular plate. Above it is the thyroid cartilage, which is the largest of all structures in the larynx. This formation consists of two plates that are combined in front at a certain angle.
Another cartilage of the larynx is the arytenoid. In its shape, it resembles a pyramid, in which a base and an apex are distinguished. Moreover, the top is turned upwards and somewhat backwards, and the base is downwards and forwards.
The most superior is the epiglottis - elastic cartilage. It closes the entrance to the larynx during swallowing, which prevents food from entering the respiratory tract.
Muscles of the larynx
Separate attention should be paid to the muscles of the larynx. They are divided into two types: own and skeletal. Muscles of the first variety are attached tothe cartilages of the larynx outside at one end, and at the other they are attached to the bones of the skeleton (sternum, collarbone, lower jaw, scapula, etc.). These muscles include:
- shirohyoid;
- sternothyroid;
- sternohyoid;
- digastric;
- scapular-hyoid;
- awl-hyoid.
Own muscles are divided into internal and external. Moreover, there are only two external muscles - the paired cricoid-thyroid.
Internal muscles are divided into several groups depending on their functional characteristics:
- muscles that regulate the width of the entrance to the larynx;
- muscles that control and change the state of the vocal cords;
- muscles of the epiglottis.
Blood vessels
The blood supply of the larynx is quite plentiful. She receives blood from the laryngeal arteries: upper and lower. The superior laryngeal artery, in turn, branches off from the superior thyroid artery. It occurs slightly above the edge of the thyroid cartilage. In the sublingual-thyroid septum there is a hole through which this artery penetrates the wall of the larynx.
On the opposite side is the same superior laryngeal artery. They anostomose, that is, they connect with each other, giving another branch to the inside of the larynx. The middle laryngeal vessel also departs from the superior thyroid artery.
The inferior laryngeal artery branches off, respectively, from the inferior thyroid vessel. The latter, in turn, departs fromsubclavian artery. In the larynx, the lower vessel passes behind the joint between the thyroid and cricoid cartilage, supplying blood to the posterior surface of the larynx. This artery forms anastomoses with the upper and middle vessels.
Thus, oxygenated blood flows through the arteries to the cartilage and muscles of the larynx. Oxygen-poor blood exits the laryngeal structures through the veins of the same name. It is collected in the venous plexuses, which then pass into the upper and lower laryngeal veins. They, in turn, flow into the superior and inferior thyroid veins. The superior vessel then carries blood to the internal jugular vein. The inferior vessel is a tributary of the brachiocephalic vein.
Innervation of the larynx
The transmission of nerve impulses to the skeletal muscles of the larynx is carried out by the branches of the vagus nerve (10 pairs of cranial nerves). The superior laryngeal nerve belongs to the mixed group. This means that both motor and sensory innervation of the larynx is carried out at its expense. That is, it takes part in the movement of the muscles, carrying an impulse to the larynx, and also carries an impulse from it to the organs of the central nervous system.
The superior laryngeal nerve branches off from the vagus nerve at the level of its inferior node. It goes down and branches into two branches, a little before reaching the level of the hyoid bone. These branches include:
- external - performs a motor function, while it carries an impulse to only one muscle - the anterior cricoid, and also innervates the lower pharyngeal constrictor;
- internal -is sensitive, penetrates into the larynx together with the superior laryngeal artery through a hole in the thyroid-sublingual membrane, innervates the mucous membrane of the organ; thus the sensitive innervation of the larynx is carried out.
The lower laryngeal nerve is purely motor. It provides contraction of all the muscles of the larynx, in addition to the anterior cricoid.
Recurrent laryngeal nerves
The right and left recurrent nerves play an essential role in the innervation of the larynx. The right one branches off from the vagus nerve at the level of its intersection with the subclavian artery. Rounding this vessel, the artery rises further along the side wall of the larynx. The left recurrent nerve also arises from the vagus nerve, but at the level of the ductus botalis, which is obliterated in children shortly after birth.
When these nerves are damaged, voice production and breathing are disturbed, as they innervate the vocal cords.
Thus, the larynx is innervated by the following nerves:
- inferior and superior laryngeal nerves;
- right and left recurrent laryngeal nerves.
